[mirror_ubuntu-artful-kernel.git] / drivers / nfc / trf7970a.c

/*
 * TI TRF7970a RFID/NFC Transceiver Driver
 *
 * Copyright (C) 2013 Texas Instruments Incorporated - http://www.ti.com
 *
 * Author: Erick Macias <emacias@ti.com>
 * Author: Felipe Balbi <balbi@ti.com>
 * Author: Mark A. Greer <mgreer@animalcreek.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2  of
 * the License as published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/device.h>
#include <linux/netdevice.h>
#include <linux/interrupt.h>
#include <linux/pm_runtime.h>
#include <linux/nfc.h>
#include <linux/skbuff.h>
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/spi/spi.h>
#include <linux/regulator/consumer.h>

#include <net/nfc/nfc.h>
#include <net/nfc/digital.h>

/* There are 3 ways the host can communicate with the trf7970a:
 * parallel mode, SPI with Slave Select (SS) mode, and SPI without
 * SS mode.  The driver only supports the two SPI modes.
 *
 * The trf7970a is very timing sensitive and the VIN, EN2, and EN
 * pins must asserted in that order and with specific delays in between.
 * The delays used in the driver were provided by TI and have been
 * confirmed to work with this driver.  There is a bug with the current
 * version of the trf7970a that requires that EN2 remain low no matter
 * what.  If it goes high, it will generate an RF field even when in
 * passive target mode.  TI has indicated that the chip will work okay
 * when EN2 is left low.  The 'en2-rf-quirk' device tree property
 * indicates that trf7970a currently being used has the erratum and
 * that EN2 must be kept low.
 *
 * Timeouts are implemented using the delayed workqueue kernel facility.
 * Timeouts are required so things don't hang when there is no response
 * from the trf7970a (or tag).  Using this mechanism creates a race with
 * interrupts, however.  That is, an interrupt and a timeout could occur
 * closely enough together that one is blocked by the mutex while the other
 * executes.  When the timeout handler executes first and blocks the
 * interrupt handler, it will eventually set the state to IDLE so the
 * interrupt handler will check the state and exit with no harm done.
 * When the interrupt handler executes first and blocks the timeout handler,
 * the cancel_delayed_work() call will know that it didn't cancel the
 * work item (i.e., timeout) and will return zero.  That return code is
 * used by the timer handler to indicate that it should ignore the timeout
 * once its unblocked.
 *
 * Aborting an active command isn't as simple as it seems because the only
 * way to abort a command that's already been sent to the tag is so turn
 * off power to the tag.  If we do that, though, we'd have to go through
 * the entire anticollision procedure again but the digital layer doesn't
 * support that.  So, if an abort is received before trf7970a_in_send_cmd()
 * has sent the command to the tag, it simply returns -ECANCELED.  If the
 * command has already been sent to the tag, then the driver continues
 * normally and recieves the response data (or error) but just before
 * sending the data upstream, it frees the rx_skb and sends -ECANCELED
 * upstream instead.  If the command failed, that error will be sent
 * upstream.
 *
 * When recieving data from a tag and the interrupt status register has
 * only the SRX bit set, it means that all of the data has been received
 * (once what's in the fifo has been read).  However, depending on timing
 * an interrupt status with only the SRX bit set may not be recived.  In
 * those cases, the timeout mechanism is used to wait 20 ms in case more
 * data arrives.  After 20 ms, it is assumed that all of the data has been
 * received and the accumulated rx data is sent upstream.  The
 * 'TRF7970A_ST_WAIT_FOR_RX_DATA_CONT' state is used for this purpose
 * (i.e., it indicates that some data has been received but we're not sure
 * if there is more coming so a timeout in this state means all data has
 * been received and there isn't an error).  The delay is 20 ms since delays
 * of ~16 ms have been observed during testing.
 *
 * Type 2 write and sector select commands respond with a 4-bit ACK or NACK.
 * Having only 4 bits in the FIFO won't normally generate an interrupt so
 * driver enables the '4_bit_RX' bit of the Special Functions register 1
 * to cause an interrupt in that case.  Leaving that bit for a read command
 * messes up the data returned so it is only enabled when the framing is
 * 'NFC_DIGITAL_FRAMING_NFCA_T2T' and the command is not a read command.
 * Unfortunately, that means that the driver has to peek into tx frames
 * when the framing is 'NFC_DIGITAL_FRAMING_NFCA_T2T'.  This is done by
 * the trf7970a_per_cmd_config() routine.
 *
 * ISO/IEC 15693 frames specify whether to use single or double sub-carrier
 * frequencies and whether to use low or high data rates in the flags byte
 * of the frame.  This means that the driver has to peek at all 15693 frames
 * to determine what speed to set the communication to.  In addition, write
 * and lock commands use the OPTION flag to indicate that an EOF must be
 * sent to the tag before it will send its response.  So the driver has to
 * examine all frames for that reason too.
 *
 * It is unclear how long to wait before sending the EOF.  According to the
 * Note under Table 1-1 in section 1.6 of
 * http://www.ti.com/lit/ug/scbu011/scbu011.pdf, that wait should be at least
 * 10 ms for TI Tag-it HF-I tags; however testing has shown that is not long
 * enough.  For this reason, the driver waits 20 ms which seems to work
 * reliably.
 */

#define TRF7970A_SUPPORTED_PROTOCOLS \
                (NFC_PROTO_MIFARE_MASK | NFC_PROTO_ISO14443_MASK |      \
                 NFC_PROTO_ISO14443_B_MASK | NFC_PROTO_FELICA_MASK | \
                 NFC_PROTO_ISO15693_MASK)

#define TRF7970A_AUTOSUSPEND_DELAY              30000 /* 30 seconds */

/* TX data must be prefixed with a FIFO reset cmd, a cmd that depends
 * on what the current framing is, the address of the TX length byte 1
 * register (0x1d), and the 2 byte length of the data to be transmitted.
 * That totals 5 bytes.
 */
#define TRF7970A_TX_SKB_HEADROOM                5

#define TRF7970A_RX_SKB_ALLOC_SIZE              256

#define TRF7970A_FIFO_SIZE                      127

/* TX length is 3 nibbles long ==> 4KB - 1 bytes max */
#define TRF7970A_TX_MAX                         (4096 - 1)

#define TRF7970A_WAIT_FOR_RX_DATA_TIMEOUT       20
#define TRF7970A_WAIT_FOR_FIFO_DRAIN_TIMEOUT    3
#define TRF7970A_WAIT_TO_ISSUE_ISO15693_EOF     20

/* Quirks */
/* Erratum: When reading IRQ Status register on trf7970a, we must issue a
 * read continuous command for IRQ Status and Collision Position registers.
 */
#define TRF7970A_QUIRK_IRQ_STATUS_READ          BIT(0)
#define TRF7970A_QUIRK_EN2_MUST_STAY_LOW        BIT(1)

/* Direct commands */
#define TRF7970A_CMD_IDLE                       0x00
#define TRF7970A_CMD_SOFT_INIT                  0x03
#define TRF7970A_CMD_RF_COLLISION               0x04
#define TRF7970A_CMD_RF_COLLISION_RESPONSE_N    0x05
#define TRF7970A_CMD_RF_COLLISION_RESPONSE_0    0x06
#define TRF7970A_CMD_FIFO_RESET                 0x0f
#define TRF7970A_CMD_TRANSMIT_NO_CRC            0x10
#define TRF7970A_CMD_TRANSMIT                   0x11
#define TRF7970A_CMD_DELAY_TRANSMIT_NO_CRC      0x12
#define TRF7970A_CMD_DELAY_TRANSMIT             0x13
#define TRF7970A_CMD_EOF                        0x14
#define TRF7970A_CMD_CLOSE_SLOT                 0x15
#define TRF7970A_CMD_BLOCK_RX                   0x16
#define TRF7970A_CMD_ENABLE_RX                  0x17
#define TRF7970A_CMD_TEST_EXT_RF                0x18
#define TRF7970A_CMD_TEST_INT_RF                0x19
#define TRF7970A_CMD_RX_GAIN_ADJUST             0x1a

/* Bits determining whether its a direct command or register R/W,
 * whether to use a continuous SPI transaction or not, and the actual
 * direct cmd opcode or regster address.
 */
#define TRF7970A_CMD_BIT_CTRL                   BIT(7)
#define TRF7970A_CMD_BIT_RW                     BIT(6)
#define TRF7970A_CMD_BIT_CONTINUOUS             BIT(5)
#define TRF7970A_CMD_BIT_OPCODE(opcode)         ((opcode) & 0x1f)

/* Registers addresses */
#define TRF7970A_CHIP_STATUS_CTRL               0x00
#define TRF7970A_ISO_CTRL                       0x01
#define TRF7970A_ISO14443B_TX_OPTIONS           0x02
#define TRF7970A_ISO14443A_HIGH_BITRATE_OPTIONS 0x03
#define TRF7970A_TX_TIMER_SETTING_H_BYTE        0x04
#define TRF7970A_TX_TIMER_SETTING_L_BYTE        0x05
#define TRF7970A_TX_PULSE_LENGTH_CTRL           0x06
#define TRF7970A_RX_NO_RESPONSE_WAIT            0x07
#define TRF7970A_RX_WAIT_TIME                   0x08
#define TRF7970A_MODULATOR_SYS_CLK_CTRL         0x09
#define TRF7970A_RX_SPECIAL_SETTINGS            0x0a
#define TRF7970A_REG_IO_CTRL                    0x0b
#define TRF7970A_IRQ_STATUS                     0x0c
#define TRF7970A_COLLISION_IRQ_MASK             0x0d
#define TRF7970A_COLLISION_POSITION             0x0e
#define TRF7970A_RSSI_OSC_STATUS                0x0f
#define TRF7970A_SPECIAL_FCN_REG1               0x10
#define TRF7970A_SPECIAL_FCN_REG2               0x11
#define TRF7970A_RAM1                           0x12
#define TRF7970A_RAM2                           0x13
#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS      0x14
#define TRF7970A_NFC_LOW_FIELD_LEVEL            0x16
#define TRF7970A_NFCID1                         0x17
#define TRF7970A_NFC_TARGET_LEVEL               0x18
#define TRF79070A_NFC_TARGET_PROTOCOL           0x19
#define TRF7970A_TEST_REGISTER1                 0x1a
#define TRF7970A_TEST_REGISTER2                 0x1b
#define TRF7970A_FIFO_STATUS                    0x1c
#define TRF7970A_TX_LENGTH_BYTE1                0x1d
#define TRF7970A_TX_LENGTH_BYTE2                0x1e
#define TRF7970A_FIFO_IO_REGISTER               0x1f

/* Chip Status Control Register Bits */
#define TRF7970A_CHIP_STATUS_VRS5_3             BIT(0)
#define TRF7970A_CHIP_STATUS_REC_ON             BIT(1)
#define TRF7970A_CHIP_STATUS_AGC_ON             BIT(2)
#define TRF7970A_CHIP_STATUS_PM_ON              BIT(3)
#define TRF7970A_CHIP_STATUS_RF_PWR             BIT(4)
#define TRF7970A_CHIP_STATUS_RF_ON              BIT(5)
#define TRF7970A_CHIP_STATUS_DIRECT             BIT(6)
#define TRF7970A_CHIP_STATUS_STBY               BIT(7)

/* ISO Control Register Bits */
#define TRF7970A_ISO_CTRL_15693_SGL_1OF4_662    0x00
#define TRF7970A_ISO_CTRL_15693_SGL_1OF256_662  0x01
#define TRF7970A_ISO_CTRL_15693_SGL_1OF4_2648   0x02
#define TRF7970A_ISO_CTRL_15693_SGL_1OF256_2648 0x03
#define TRF7970A_ISO_CTRL_15693_DBL_1OF4_667a   0x04
#define TRF7970A_ISO_CTRL_15693_DBL_1OF256_667  0x05
#define TRF7970A_ISO_CTRL_15693_DBL_1OF4_2669   0x06
#define TRF7970A_ISO_CTRL_15693_DBL_1OF256_2669 0x07
#define TRF7970A_ISO_CTRL_14443A_106            0x08
#define TRF7970A_ISO_CTRL_14443A_212            0x09
#define TRF7970A_ISO_CTRL_14443A_424            0x0a
#define TRF7970A_ISO_CTRL_14443A_848            0x0b
#define TRF7970A_ISO_CTRL_14443B_106            0x0c
#define TRF7970A_ISO_CTRL_14443B_212            0x0d
#define TRF7970A_ISO_CTRL_14443B_424            0x0e
#define TRF7970A_ISO_CTRL_14443B_848            0x0f
#define TRF7970A_ISO_CTRL_FELICA_212            0x1a
#define TRF7970A_ISO_CTRL_FELICA_424            0x1b
#define TRF7970A_ISO_CTRL_RFID                  BIT(5)
#define TRF7970A_ISO_CTRL_DIR_MODE              BIT(6)
#define TRF7970A_ISO_CTRL_RX_CRC_N              BIT(7)  /* true == No CRC */

#define TRF7970A_ISO_CTRL_RFID_SPEED_MASK       0x1f

/* Modulator and SYS_CLK Control Register Bits */
#define TRF7970A_MODULATOR_DEPTH(n)             ((n) & 0x7)
#define TRF7970A_MODULATOR_DEPTH_ASK10          (TRF7970A_MODULATOR_DEPTH(0))
#define TRF7970A_MODULATOR_DEPTH_OOK            (TRF7970A_MODULATOR_DEPTH(1))
#define TRF7970A_MODULATOR_DEPTH_ASK7           (TRF7970A_MODULATOR_DEPTH(2))
#define TRF7970A_MODULATOR_DEPTH_ASK8_5         (TRF7970A_MODULATOR_DEPTH(3))
#define TRF7970A_MODULATOR_DEPTH_ASK13          (TRF7970A_MODULATOR_DEPTH(4))
#define TRF7970A_MODULATOR_DEPTH_ASK16          (TRF7970A_MODULATOR_DEPTH(5))
#define TRF7970A_MODULATOR_DEPTH_ASK22          (TRF7970A_MODULATOR_DEPTH(6))
#define TRF7970A_MODULATOR_DEPTH_ASK30          (TRF7970A_MODULATOR_DEPTH(7))
#define TRF7970A_MODULATOR_EN_ANA               BIT(3)
#define TRF7970A_MODULATOR_CLK(n)               (((n) & 0x3) << 4)
#define TRF7970A_MODULATOR_CLK_DISABLED         (TRF7970A_MODULATOR_CLK(0))
#define TRF7970A_MODULATOR_CLK_3_6              (TRF7970A_MODULATOR_CLK(1))
#define TRF7970A_MODULATOR_CLK_6_13             (TRF7970A_MODULATOR_CLK(2))
#define TRF7970A_MODULATOR_CLK_13_27            (TRF7970A_MODULATOR_CLK(3))
#define TRF7970A_MODULATOR_EN_OOK               BIT(6)
#define TRF7970A_MODULATOR_27MHZ                BIT(7)

/* IRQ Status Register Bits */
#define TRF7970A_IRQ_STATUS_NORESP              BIT(0) /* ISO15693 only */
#define TRF7970A_IRQ_STATUS_COL                 BIT(1)
#define TRF7970A_IRQ_STATUS_FRAMING_EOF_ERROR   BIT(2)
#define TRF7970A_IRQ_STATUS_PARITY_ERROR        BIT(3)
#define TRF7970A_IRQ_STATUS_CRC_ERROR           BIT(4)
#define TRF7970A_IRQ_STATUS_FIFO                BIT(5)
#define TRF7970A_IRQ_STATUS_SRX                 BIT(6)
#define TRF7970A_IRQ_STATUS_TX                  BIT(7)

#define TRF7970A_IRQ_STATUS_ERROR                               \
                (TRF7970A_IRQ_STATUS_COL |                      \
                 TRF7970A_IRQ_STATUS_FRAMING_EOF_ERROR |        \
                 TRF7970A_IRQ_STATUS_PARITY_ERROR |             \
                 TRF7970A_IRQ_STATUS_CRC_ERROR)

#define TRF7970A_SPECIAL_FCN_REG1_COL_7_6               BIT(0)
#define TRF7970A_SPECIAL_FCN_REG1_14_ANTICOLL           BIT(1)
#define TRF7970A_SPECIAL_FCN_REG1_4_BIT_RX              BIT(2)
#define TRF7970A_SPECIAL_FCN_REG1_SP_DIR_MODE           BIT(3)
#define TRF7970A_SPECIAL_FCN_REG1_NEXT_SLOT_37US        BIT(4)
#define TRF7970A_SPECIAL_FCN_REG1_PAR43                 BIT(5)

#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLH_124      (0x0 << 2)
#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLH_120      (0x1 << 2)
#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLH_112      (0x2 << 2)
#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLH_96       (0x3 << 2)
#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLL_4        0x0
#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLL_8        0x1
#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLL_16       0x2
#define TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLL_32       0x3

#define TRF7970A_FIFO_STATUS_OVERFLOW           BIT(7)

/* NFC (ISO/IEC 14443A) Type 2 Tag commands */
#define NFC_T2T_CMD_READ                        0x30

/* ISO 15693 commands codes */
#define ISO15693_CMD_INVENTORY                  0x01
#define ISO15693_CMD_READ_SINGLE_BLOCK          0x20
#define ISO15693_CMD_WRITE_SINGLE_BLOCK         0x21
#define ISO15693_CMD_LOCK_BLOCK                 0x22
#define ISO15693_CMD_READ_MULTIPLE_BLOCK        0x23
#define ISO15693_CMD_WRITE_MULTIPLE_BLOCK       0x24
#define ISO15693_CMD_SELECT                     0x25
#define ISO15693_CMD_RESET_TO_READY             0x26
#define ISO15693_CMD_WRITE_AFI                  0x27
#define ISO15693_CMD_LOCK_AFI                   0x28
#define ISO15693_CMD_WRITE_DSFID                0x29
#define ISO15693_CMD_LOCK_DSFID                 0x2a
#define ISO15693_CMD_GET_SYSTEM_INFO            0x2b
#define ISO15693_CMD_GET_MULTIPLE_BLOCK_SECURITY_STATUS 0x2c

/* ISO 15693 request and response flags */
#define ISO15693_REQ_FLAG_SUB_CARRIER           BIT(0)
#define ISO15693_REQ_FLAG_DATA_RATE             BIT(1)
#define ISO15693_REQ_FLAG_INVENTORY             BIT(2)
#define ISO15693_REQ_FLAG_PROTOCOL_EXT          BIT(3)
#define ISO15693_REQ_FLAG_SELECT                BIT(4)
#define ISO15693_REQ_FLAG_AFI                   BIT(4)
#define ISO15693_REQ_FLAG_ADDRESS               BIT(5)
#define ISO15693_REQ_FLAG_NB_SLOTS              BIT(5)
#define ISO15693_REQ_FLAG_OPTION                BIT(6)

#define ISO15693_REQ_FLAG_SPEED_MASK \
                (ISO15693_REQ_FLAG_SUB_CARRIER | ISO15693_REQ_FLAG_DATA_RATE)

enum trf7970a_state {
        TRF7970A_ST_OFF,
        TRF7970A_ST_IDLE,
        TRF7970A_ST_IDLE_RX_BLOCKED,
        TRF7970A_ST_WAIT_FOR_TX_FIFO,
        TRF7970A_ST_WAIT_FOR_RX_DATA,
        TRF7970A_ST_WAIT_FOR_RX_DATA_CONT,
        TRF7970A_ST_WAIT_TO_ISSUE_EOF,
        TRF7970A_ST_MAX
};

struct trf7970a {
        enum trf7970a_state             state;
        struct device                   *dev;
        struct spi_device               *spi;
        struct regulator                *regulator;
        struct nfc_digital_dev          *ddev;
        u32                             quirks;
        bool                            aborting;
        struct sk_buff                  *tx_skb;
        struct sk_buff                  *rx_skb;
        nfc_digital_cmd_complete_t      cb;
        void                            *cb_arg;
        u8                              chip_status_ctrl;
        u8                              iso_ctrl;
        u8                              iso_ctrl_tech;
        u8                              modulator_sys_clk_ctrl;
        u8                              special_fcn_reg1;
        int                             technology;
        int                             framing;
        u8                              tx_cmd;
        bool                            issue_eof;
        int                             en2_gpio;
        int                             en_gpio;
        struct mutex                    lock;
        unsigned int                    timeout;
        bool                            ignore_timeout;
        struct delayed_work             timeout_work;
};


static int trf7970a_cmd(struct trf7970a *trf, u8 opcode)
{
        u8 cmd = TRF7970A_CMD_BIT_CTRL | TRF7970A_CMD_BIT_OPCODE(opcode);
        int ret;

        dev_dbg(trf->dev, "cmd: 0x%x\n", cmd);

        ret = spi_write(trf->spi, &cmd, 1);
        if (ret)
                dev_err(trf->dev, "%s - cmd: 0x%x, ret: %d\n", __func__, cmd,
                                ret);
        return ret;
}

static int trf7970a_read(struct trf7970a *trf, u8 reg, u8 *val)
{
        u8 addr = TRF7970A_CMD_BIT_RW | reg;
        int ret;

        ret = spi_write_then_read(trf->spi, &addr, 1, val, 1);
        if (ret)
                dev_err(trf->dev, "%s - addr: 0x%x, ret: %d\n", __func__, addr,
                                ret);

        dev_dbg(trf->dev, "read(0x%x): 0x%x\n", addr, *val);

        return ret;
}

static int trf7970a_read_cont(struct trf7970a *trf, u8 reg, u8 *buf, size_t len)
{
        u8 addr = reg | TRF7970A_CMD_BIT_RW | TRF7970A_CMD_BIT_CONTINUOUS;
        struct spi_transfer t[2];
        struct spi_message m;
        int ret;

        dev_dbg(trf->dev, "read_cont(0x%x, %zd)\n", addr, len);

        spi_message_init(&m);

        memset(&t, 0, sizeof(t));

        t[0].tx_buf = &addr;
        t[0].len = sizeof(addr);
        spi_message_add_tail(&t[0], &m);

        t[1].rx_buf = buf;
        t[1].len = len;
        spi_message_add_tail(&t[1], &m);

        ret = spi_sync(trf->spi, &m);
        if (ret)
                dev_err(trf->dev, "%s - addr: 0x%x, ret: %d\n", __func__, addr,
                                ret);
        return ret;
}

static int trf7970a_write(struct trf7970a *trf, u8 reg, u8 val)
{
        u8 buf[2] = { reg, val };
        int ret;

        dev_dbg(trf->dev, "write(0x%x): 0x%x\n", reg, val);

        ret = spi_write(trf->spi, buf, 2);
        if (ret)
                dev_err(trf->dev, "%s - write: 0x%x 0x%x, ret: %d\n", __func__,
                                buf[0], buf[1], ret);

        return ret;
}

static int trf7970a_read_irqstatus(struct trf7970a *trf, u8 *status)
{
        int ret;
        u8 buf[2];
        u8 addr;

        addr = TRF7970A_IRQ_STATUS | TRF7970A_CMD_BIT_RW;

        if (trf->quirks & TRF7970A_QUIRK_IRQ_STATUS_READ) {
                addr |= TRF7970A_CMD_BIT_CONTINUOUS;
                ret = spi_write_then_read(trf->spi, &addr, 1, buf, 2);
        } else {
                ret = spi_write_then_read(trf->spi, &addr, 1, buf, 1);
        }

        if (ret)
                dev_err(trf->dev, "%s - irqstatus: Status read failed: %d\n",
                                __func__, ret);
        else
                *status = buf[0];

        return ret;
}

static void trf7970a_send_upstream(struct trf7970a *trf)
{
        u8 rssi;

        dev_kfree_skb_any(trf->tx_skb);
        trf->tx_skb = NULL;

        if (trf->rx_skb && !IS_ERR(trf->rx_skb) && !trf->aborting)
                print_hex_dump_debug("trf7970a rx data: ", DUMP_PREFIX_NONE,
                                16, 1, trf->rx_skb->data, trf->rx_skb->len,
                                false);

        /* According to the manual it is "good form" to reset the fifo and
         * read the RSSI levels & oscillator status register here.  It doesn't
         * explain why.
         */
        trf7970a_cmd(trf, TRF7970A_CMD_FIFO_RESET);
        trf7970a_read(trf, TRF7970A_RSSI_OSC_STATUS, &rssi);

        trf->state = TRF7970A_ST_IDLE;

        if (trf->aborting) {
                dev_dbg(trf->dev, "Abort process complete\n");

                if (!IS_ERR(trf->rx_skb)) {
                        kfree_skb(trf->rx_skb);
                        trf->rx_skb = ERR_PTR(-ECANCELED);
                }

                trf->aborting = false;
        }

        trf->cb(trf->ddev, trf->cb_arg, trf->rx_skb);

        trf->rx_skb = NULL;
}

static void trf7970a_send_err_upstream(struct trf7970a *trf, int errno)
{
        dev_dbg(trf->dev, "Error - state: %d, errno: %d\n", trf->state, errno);

        kfree_skb(trf->rx_skb);
        trf->rx_skb = ERR_PTR(errno);

        trf7970a_send_upstream(trf);
}

static int trf7970a_transmit(struct trf7970a *trf, struct sk_buff *skb,
                unsigned int len)
{
        unsigned int timeout;
        int ret;

        print_hex_dump_debug("trf7970a tx data: ", DUMP_PREFIX_NONE,
                        16, 1, skb->data, len, false);

        ret = spi_write(trf->spi, skb->data, len);
        if (ret) {
                dev_err(trf->dev, "%s - Can't send tx data: %d\n", __func__,
                                ret);
                return ret;
        }

        skb_pull(skb, len);

        if (skb->len > 0) {
                trf->state = TRF7970A_ST_WAIT_FOR_TX_FIFO;
                timeout = TRF7970A_WAIT_FOR_FIFO_DRAIN_TIMEOUT;
        } else {
                if (trf->issue_eof) {
                        trf->state = TRF7970A_ST_WAIT_TO_ISSUE_EOF;
                        timeout = TRF7970A_WAIT_TO_ISSUE_ISO15693_EOF;
                } else {
                        trf->state = TRF7970A_ST_WAIT_FOR_RX_DATA;
                        timeout = trf->timeout;
                }
        }

        dev_dbg(trf->dev, "Setting timeout for %d ms, state: %d\n", timeout,
                        trf->state);

        schedule_delayed_work(&trf->timeout_work, msecs_to_jiffies(timeout));

        return 0;
}

static void trf7970a_fill_fifo(struct trf7970a *trf)
{
        struct sk_buff *skb = trf->tx_skb;
        unsigned int len;
        int ret;
        u8 fifo_bytes;

        ret = trf7970a_read(trf, TRF7970A_FIFO_STATUS, &fifo_bytes);
        if (ret) {
                trf7970a_send_err_upstream(trf, ret);
                return;
        }

        dev_dbg(trf->dev, "Filling FIFO - fifo_bytes: 0x%x\n", fifo_bytes);

        fifo_bytes &= ~TRF7970A_FIFO_STATUS_OVERFLOW;

        /* Calculate how much more data can be written to the fifo */
        len = TRF7970A_FIFO_SIZE - fifo_bytes;
        len = min(skb->len, len);

        ret = trf7970a_transmit(trf, skb, len);
        if (ret)
                trf7970a_send_err_upstream(trf, ret);
}

static void trf7970a_drain_fifo(struct trf7970a *trf, u8 status)
{
        struct sk_buff *skb = trf->rx_skb;
        int ret;
        u8 fifo_bytes;

        if (status & TRF7970A_IRQ_STATUS_ERROR) {
                trf7970a_send_err_upstream(trf, -EIO);
                return;
        }

        ret = trf7970a_read(trf, TRF7970A_FIFO_STATUS, &fifo_bytes);
        if (ret) {
                trf7970a_send_err_upstream(trf, ret);
                return;
        }

        dev_dbg(trf->dev, "Draining FIFO - fifo_bytes: 0x%x\n", fifo_bytes);

        fifo_bytes &= ~TRF7970A_FIFO_STATUS_OVERFLOW;

        if (!fifo_bytes)
                goto no_rx_data;

        if (fifo_bytes > skb_tailroom(skb)) {
                skb = skb_copy_expand(skb, skb_headroom(skb),
                                max_t(int, fifo_bytes,
                                        TRF7970A_RX_SKB_ALLOC_SIZE),
                                GFP_KERNEL);
                if (!skb) {
                        trf7970a_send_err_upstream(trf, -ENOMEM);
                        return;
                }

                kfree_skb(trf->rx_skb);
                trf->rx_skb = skb;
        }

        ret = trf7970a_read_cont(trf, TRF7970A_FIFO_IO_REGISTER,
                        skb_put(skb, fifo_bytes), fifo_bytes);
        if (ret) {
                trf7970a_send_err_upstream(trf, ret);
                return;
        }

        /* If received Type 2 ACK/NACK, shift right 4 bits and pass up */
        if ((trf->framing == NFC_DIGITAL_FRAMING_NFCA_T2T) && (skb->len == 1) &&
                        (trf->special_fcn_reg1 ==
                                 TRF7970A_SPECIAL_FCN_REG1_4_BIT_RX)) {
                skb->data[0] >>= 4;
                status = TRF7970A_IRQ_STATUS_SRX;
        } else {
                trf->state = TRF7970A_ST_WAIT_FOR_RX_DATA_CONT;
        }

no_rx_data:
        if (status == TRF7970A_IRQ_STATUS_SRX) { /* Receive complete */
                trf7970a_send_upstream(trf);
                return;
        }

        dev_dbg(trf->dev, "Setting timeout for %d ms\n",
                        TRF7970A_WAIT_FOR_RX_DATA_TIMEOUT);

        schedule_delayed_work(&trf->timeout_work,
                        msecs_to_jiffies(TRF7970A_WAIT_FOR_RX_DATA_TIMEOUT));
}

static irqreturn_t trf7970a_irq(int irq, void *dev_id)
{
        struct trf7970a *trf = dev_id;
        int ret;
        u8 status;

        mutex_lock(&trf->lock);

        if (trf->state == TRF7970A_ST_OFF) {
                mutex_unlock(&trf->lock);
                return IRQ_NONE;
        }

        ret = trf7970a_read_irqstatus(trf, &status);
        if (ret) {
                mutex_unlock(&trf->lock);
                return IRQ_NONE;
        }

        dev_dbg(trf->dev, "IRQ - state: %d, status: 0x%x\n", trf->state,
                        status);

        if (!status) {
                mutex_unlock(&trf->lock);
                return IRQ_NONE;
        }

        switch (trf->state) {
        case TRF7970A_ST_IDLE:
        case TRF7970A_ST_IDLE_RX_BLOCKED:
                /* If getting interrupts caused by RF noise, turn off the
                 * receiver to avoid unnecessary interrupts.  It will be
                 * turned back on in trf7970a_in_send_cmd() when the next
                 * command is issued.
                 */
                if (status & TRF7970A_IRQ_STATUS_ERROR) {
                        trf7970a_cmd(trf, TRF7970A_CMD_BLOCK_RX);
                        trf->state = TRF7970A_ST_IDLE_RX_BLOCKED;
                }

                trf7970a_cmd(trf, TRF7970A_CMD_FIFO_RESET);
                break;
        case TRF7970A_ST_WAIT_FOR_TX_FIFO:
                if (status & TRF7970A_IRQ_STATUS_TX) {
                        trf->ignore_timeout =
                                !cancel_delayed_work(&trf->timeout_work);
                        trf7970a_fill_fifo(trf);
                } else {
                        trf7970a_send_err_upstream(trf, -EIO);
                }
                break;
        case TRF7970A_ST_WAIT_FOR_RX_DATA:
        case TRF7970A_ST_WAIT_FOR_RX_DATA_CONT:
                if (status & TRF7970A_IRQ_STATUS_SRX) {
                        trf->ignore_timeout =
                                !cancel_delayed_work(&trf->timeout_work);
                        trf7970a_drain_fifo(trf, status);
                } else if (status == TRF7970A_IRQ_STATUS_TX) {
                        trf7970a_cmd(trf, TRF7970A_CMD_FIFO_RESET);
                } else {
                        trf7970a_send_err_upstream(trf, -EIO);
                }
                break;
        case TRF7970A_ST_WAIT_TO_ISSUE_EOF:
                if (status != TRF7970A_IRQ_STATUS_TX)
                        trf7970a_send_err_upstream(trf, -EIO);
                break;
        default:
                dev_err(trf->dev, "%s - Driver in invalid state: %d\n",
                                __func__, trf->state);
        }

        mutex_unlock(&trf->lock);
        return IRQ_HANDLED;
}

static void trf7970a_issue_eof(struct trf7970a *trf)
{
        int ret;

        dev_dbg(trf->dev, "Issuing EOF\n");

        ret = trf7970a_cmd(trf, TRF7970A_CMD_FIFO_RESET);
        if (ret)
                trf7970a_send_err_upstream(trf, ret);

        ret = trf7970a_cmd(trf, TRF7970A_CMD_EOF);
        if (ret)
                trf7970a_send_err_upstream(trf, ret);

        trf->state = TRF7970A_ST_WAIT_FOR_RX_DATA;

        dev_dbg(trf->dev, "Setting timeout for %d ms, state: %d\n",
                        trf->timeout, trf->state);

        schedule_delayed_work(&trf->timeout_work,
                        msecs_to_jiffies(trf->timeout));
}

static void trf7970a_timeout_work_handler(struct work_struct *work)
{
        struct trf7970a *trf = container_of(work, struct trf7970a,
                        timeout_work.work);

        dev_dbg(trf->dev, "Timeout - state: %d, ignore_timeout: %d\n",
                        trf->state, trf->ignore_timeout);

        mutex_lock(&trf->lock);

        if (trf->ignore_timeout)
                trf->ignore_timeout = false;
        else if (trf->state == TRF7970A_ST_WAIT_FOR_RX_DATA_CONT)
                trf7970a_send_upstream(trf); /* No more rx data so send up */
        else if (trf->state == TRF7970A_ST_WAIT_TO_ISSUE_EOF)
                trf7970a_issue_eof(trf);
        else
                trf7970a_send_err_upstream(trf, -ETIMEDOUT);

        mutex_unlock(&trf->lock);
}

static int trf7970a_init(struct trf7970a *trf)
{
        int ret;

        dev_dbg(trf->dev, "Initializing device - state: %d\n", trf->state);

        ret = trf7970a_cmd(trf, TRF7970A_CMD_SOFT_INIT);
        if (ret)
                goto err_out;

        ret = trf7970a_cmd(trf, TRF7970A_CMD_IDLE);
        if (ret)
                goto err_out;

        ret = trf7970a_write(trf, TRF7970A_MODULATOR_SYS_CLK_CTRL, 0);
        if (ret)
                goto err_out;

        trf->modulator_sys_clk_ctrl = 0;

        /* Must clear NFC Target Detection Level reg due to erratum */
        ret = trf7970a_write(trf, TRF7970A_NFC_TARGET_LEVEL, 0);
        if (ret)
                goto err_out;

        ret = trf7970a_write(trf, TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS,
                        TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLH_96 |
                        TRF7970A_ADJUTABLE_FIFO_IRQ_LEVELS_WLL_32);
        if (ret)
                goto err_out;

        ret = trf7970a_write(trf, TRF7970A_SPECIAL_FCN_REG1, 0);
        if (ret)
                goto err_out;

        trf->special_fcn_reg1 = 0;

        trf->iso_ctrl = 0xff;
        return 0;

err_out:
        dev_dbg(trf->dev, "Couldn't init device: %d\n", ret);
        return ret;
}

static void trf7970a_switch_rf_off(struct trf7970a *trf)
{
        dev_dbg(trf->dev, "Switching rf off\n");

        trf->chip_status_ctrl &= ~TRF7970A_CHIP_STATUS_RF_ON;

        trf7970a_write(trf, TRF7970A_CHIP_STATUS_CTRL, trf->chip_status_ctrl);

        trf->aborting = false;
        trf->state = TRF7970A_ST_OFF;

        pm_runtime_mark_last_busy(trf->dev);
        pm_runtime_put_autosuspend(trf->dev);
}

static void trf7970a_switch_rf_on(struct trf7970a *trf)
{
        int ret;

        dev_dbg(trf->dev, "Switching rf on\n");

        pm_runtime_get_sync(trf->dev);

        ret = trf7970a_init(trf);
        if (ret) {
                dev_err(trf->dev, "%s - Can't initialize: %d\n", __func__, ret);
                return;
        }

        trf->state = TRF7970A_ST_IDLE;
}

static int trf7970a_switch_rf(struct nfc_digital_dev *ddev, bool on)
{
        struct trf7970a *trf = nfc_digital_get_drvdata(ddev);

        dev_dbg(trf->dev, "Switching RF - state: %d, on: %d\n", trf->state, on);

        mutex_lock(&trf->lock);

        if (on) {
                switch (trf->state) {
                case TRF7970A_ST_OFF:
                        trf7970a_switch_rf_on(trf);
                        break;
                case TRF7970A_ST_IDLE:
                case TRF7970A_ST_IDLE_RX_BLOCKED:
                        break;
                default:
                        dev_err(trf->dev, "%s - Invalid request: %d %d\n",
                                        __func__, trf->state, on);
                        trf7970a_switch_rf_off(trf);
                }
        } else {
                switch (trf->state) {
                case TRF7970A_ST_OFF:
                        break;
                default:
                        dev_err(trf->dev, "%s - Invalid request: %d %d\n",
                                        __func__, trf->state, on);
                        /* FALLTHROUGH */
                case TRF7970A_ST_IDLE:
                case TRF7970A_ST_IDLE_RX_BLOCKED:
                        trf7970a_switch_rf_off(trf);
                }
        }

        mutex_unlock(&trf->lock);
        return 0;
}

static int trf7970a_config_rf_tech(struct trf7970a *trf, int tech)
{
        int ret = 0;

        dev_dbg(trf->dev, "rf technology: %d\n", tech);

        switch (tech) {
        case NFC_DIGITAL_RF_TECH_106A:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_14443A_106;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_OOK;
                break;
        case NFC_DIGITAL_RF_TECH_106B:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_14443B_106;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_ASK10;
                break;
        case NFC_DIGITAL_RF_TECH_212F:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_FELICA_212;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_ASK10;
                break;
        case NFC_DIGITAL_RF_TECH_424F:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_FELICA_424;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_ASK10;
                break;
        case NFC_DIGITAL_RF_TECH_ISO15693:
                trf->iso_ctrl_tech = TRF7970A_ISO_CTRL_15693_SGL_1OF4_2648;
                trf->modulator_sys_clk_ctrl = TRF7970A_MODULATOR_DEPTH_OOK;
                break;
        default:
                dev_dbg(trf->dev, "Unsupported rf technology: %d\n", tech);
                return -EINVAL;
        }

        trf->technology = tech;

        return ret;
}

static int trf7970a_config_framing(struct trf7970a *trf, int framing)
{
        u8 iso_ctrl = trf->iso_ctrl_tech;
        int ret;

        dev_dbg(trf->dev, "framing: %d\n", framing);

        switch (framing) {
        case NFC_DIGITAL_FRAMING_NFCA_SHORT:
        case NFC_DIGITAL_FRAMING_NFCA_STANDARD:
                trf->tx_cmd = TRF7970A_CMD_TRANSMIT_NO_CRC;
                iso_ctrl |= TRF7970A_ISO_CTRL_RX_CRC_N;
                break;
        case NFC_DIGITAL_FRAMING_NFCA_STANDARD_WITH_CRC_A:
        case NFC_DIGITAL_FRAMING_NFCA_T4T:
        case NFC_DIGITAL_FRAMING_NFCB:
        case NFC_DIGITAL_FRAMING_NFCB_T4T:
        case NFC_DIGITAL_FRAMING_NFCF:
        case NFC_DIGITAL_FRAMING_NFCF_T3T:
        case NFC_DIGITAL_FRAMING_ISO15693_INVENTORY:
        case NFC_DIGITAL_FRAMING_ISO15693_T5T:
                trf->tx_cmd = TRF7970A_CMD_TRANSMIT;
                iso_ctrl &= ~TRF7970A_ISO_CTRL_RX_CRC_N;
                break;
        case NFC_DIGITAL_FRAMING_NFCA_T2T:
                trf->tx_cmd = TRF7970A_CMD_TRANSMIT;
                iso_ctrl |= TRF7970A_ISO_CTRL_RX_CRC_N;
                break;
        default:
                dev_dbg(trf->dev, "Unsupported Framing: %d\n", framing);
                return -EINVAL;
        }

        trf->framing = framing;

        if (iso_ctrl != trf->iso_ctrl) {
                ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
                if (ret)
                        return ret;

                trf->iso_ctrl = iso_ctrl;

                ret = trf7970a_write(trf, TRF7970A_MODULATOR_SYS_CLK_CTRL,
                                trf->modulator_sys_clk_ctrl);
                if (ret)
                        return ret;
        }

        if (!(trf->chip_status_ctrl & TRF7970A_CHIP_STATUS_RF_ON)) {
                ret = trf7970a_write(trf, TRF7970A_CHIP_STATUS_CTRL,
                                trf->chip_status_ctrl |
                                        TRF7970A_CHIP_STATUS_RF_ON);
                if (ret)
                        return ret;

                trf->chip_status_ctrl |= TRF7970A_CHIP_STATUS_RF_ON;

                usleep_range(5000, 6000);
        }

        return 0;
}

static int trf7970a_in_configure_hw(struct nfc_digital_dev *ddev, int type,
                int param)
{
        struct trf7970a *trf = nfc_digital_get_drvdata(ddev);
        int ret;

        dev_dbg(trf->dev, "Configure hw - type: %d, param: %d\n", type, param);

        mutex_lock(&trf->lock);

        if (trf->state == TRF7970A_ST_OFF)
                trf7970a_switch_rf_on(trf);

        switch (type) {
        case NFC_DIGITAL_CONFIG_RF_TECH:
                ret = trf7970a_config_rf_tech(trf, param);
                break;
        case NFC_DIGITAL_CONFIG_FRAMING:
                ret = trf7970a_config_framing(trf, param);
                break;
        default:
                dev_dbg(trf->dev, "Unknown type: %d\n", type);
                ret = -EINVAL;
        }

        mutex_unlock(&trf->lock);
        return ret;
}

static int trf7970a_is_iso15693_write_or_lock(u8 cmd)
{
        switch (cmd) {
        case ISO15693_CMD_WRITE_SINGLE_BLOCK:
        case ISO15693_CMD_LOCK_BLOCK:
        case ISO15693_CMD_WRITE_MULTIPLE_BLOCK:
        case ISO15693_CMD_WRITE_AFI:
        case ISO15693_CMD_LOCK_AFI:
        case ISO15693_CMD_WRITE_DSFID:
        case ISO15693_CMD_LOCK_DSFID:
                return 1;
                break;
        default:
                return 0;
        }
}

static int trf7970a_per_cmd_config(struct trf7970a *trf, struct sk_buff *skb)
{
        u8 *req = skb->data;
        u8 special_fcn_reg1, iso_ctrl;
        int ret;

        trf->issue_eof = false;

        /* When issuing Type 2 read command, make sure the '4_bit_RX' bit in
         * special functions register 1 is cleared; otherwise, its a write or
         * sector select command and '4_bit_RX' must be set.
         *
         * When issuing an ISO 15693 command, inspect the flags byte to see
         * what speed to use.  Also, remember if the OPTION flag is set on
         * a Type 5 write or lock command so the driver will know that it
         * has to send an EOF in order to get a response.
         */
        if ((trf->technology == NFC_DIGITAL_RF_TECH_106A) &&
                        (trf->framing == NFC_DIGITAL_FRAMING_NFCA_T2T)) {
                if (req[0] == NFC_T2T_CMD_READ)
                        special_fcn_reg1 = 0;
                else
                        special_fcn_reg1 = TRF7970A_SPECIAL_FCN_REG1_4_BIT_RX;

                if (special_fcn_reg1 != trf->special_fcn_reg1) {
                        ret = trf7970a_write(trf, TRF7970A_SPECIAL_FCN_REG1,
                                        special_fcn_reg1);
                        if (ret)
                                return ret;

                        trf->special_fcn_reg1 = special_fcn_reg1;
                }
        } else if (trf->technology == NFC_DIGITAL_RF_TECH_ISO15693) {
                iso_ctrl = trf->iso_ctrl & ~TRF7970A_ISO_CTRL_RFID_SPEED_MASK;

                switch (req[0] & ISO15693_REQ_FLAG_SPEED_MASK) {
                case 0x00:
                        iso_ctrl |= TRF7970A_ISO_CTRL_15693_SGL_1OF4_662;
                        break;
                case ISO15693_REQ_FLAG_SUB_CARRIER:
                        iso_ctrl |= TRF7970A_ISO_CTRL_15693_DBL_1OF4_667a;
                        break;
                case ISO15693_REQ_FLAG_DATA_RATE:
                        iso_ctrl |= TRF7970A_ISO_CTRL_15693_SGL_1OF4_2648;
                        break;
                case (ISO15693_REQ_FLAG_SUB_CARRIER |
                                ISO15693_REQ_FLAG_DATA_RATE):
                        iso_ctrl |= TRF7970A_ISO_CTRL_15693_DBL_1OF4_2669;
                        break;
                }

                if (iso_ctrl != trf->iso_ctrl) {
                        ret = trf7970a_write(trf, TRF7970A_ISO_CTRL, iso_ctrl);
                        if (ret)
                                return ret;

                        trf->iso_ctrl = iso_ctrl;
                }

                if ((trf->framing == NFC_DIGITAL_FRAMING_ISO15693_T5T) &&
                                trf7970a_is_iso15693_write_or_lock(req[1]) &&
                                (req[0] & ISO15693_REQ_FLAG_OPTION))
                        trf->issue_eof = true;
        }

        return 0;
}

static int trf7970a_in_send_cmd(struct nfc_digital_dev *ddev,
                struct sk_buff *skb, u16 timeout,
                nfc_digital_cmd_complete_t cb, void *arg)
{
        struct trf7970a *trf = nfc_digital_get_drvdata(ddev);
        char *prefix;
        unsigned int len;
        int ret;

        dev_dbg(trf->dev, "New request - state: %d, timeout: %d ms, len: %d\n",
                        trf->state, timeout, skb->len);

        if (skb->len > TRF7970A_TX_MAX)
                return -EINVAL;

        mutex_lock(&trf->lock);

        if ((trf->state != TRF7970A_ST_IDLE) &&
                        (trf->state != TRF7970A_ST_IDLE_RX_BLOCKED)) {
                dev_err(trf->dev, "%s - Bogus state: %d\n", __func__,
                                trf->state);
                ret = -EIO;
                goto out_err;
        }

        if (trf->aborting) {
                dev_dbg(trf->dev, "Abort process complete\n");
                trf->aborting = false;
                ret = -ECANCELED;
                goto out_err;
        }

        trf->rx_skb = nfc_alloc_recv_skb(TRF7970A_RX_SKB_ALLOC_SIZE,
                        GFP_KERNEL);
        if (!trf->rx_skb) {
                dev_dbg(trf->dev, "Can't alloc rx_skb\n");
                ret = -ENOMEM;
                goto out_err;
        }

        if (trf->state == TRF7970A_ST_IDLE_RX_BLOCKED) {
                ret = trf7970a_cmd(trf, TRF7970A_CMD_ENABLE_RX);
                if (ret)
                        goto out_err;

                trf->state = TRF7970A_ST_IDLE;
        }

        ret = trf7970a_per_cmd_config(trf, skb);
        if (ret)
                goto out_err;

        trf->ddev = ddev;
        trf->tx_skb = skb;
        trf->cb = cb;
        trf->cb_arg = arg;
        trf->timeout = timeout;
        trf->ignore_timeout = false;

        len = skb->len;
        prefix = skb_push(skb, TRF7970A_TX_SKB_HEADROOM);

        /* TX data must be prefixed with a FIFO reset cmd, a cmd that depends
         * on what the current framing is, the address of the TX length byte 1
         * register (0x1d), and the 2 byte length of the data to be transmitted.
         */
        prefix[0] = TRF7970A_CMD_BIT_CTRL |
                        TRF7970A_CMD_BIT_OPCODE(TRF7970A_CMD_FIFO_RESET);
        prefix[1] = TRF7970A_CMD_BIT_CTRL |
                        TRF7970A_CMD_BIT_OPCODE(trf->tx_cmd);
        prefix[2] = TRF7970A_CMD_BIT_CONTINUOUS | TRF7970A_TX_LENGTH_BYTE1;

        if (trf->framing == NFC_DIGITAL_FRAMING_NFCA_SHORT) {
                prefix[3] = 0x00;
                prefix[4] = 0x0f; /* 7 bits */
        } else {
                prefix[3] = (len & 0xf00) >> 4;
                prefix[3] |= ((len & 0xf0) >> 4);
                prefix[4] = ((len & 0x0f) << 4);
        }

        len = min_t(int, skb->len, TRF7970A_FIFO_SIZE);

        ret = trf7970a_transmit(trf, skb, len);
        if (ret) {
                kfree_skb(trf->rx_skb);
                trf->rx_skb = NULL;
        }

out_err:
        mutex_unlock(&trf->lock);
        return ret;
}

static int trf7970a_tg_configure_hw(struct nfc_digital_dev *ddev,
                int type, int param)
{
        struct trf7970a *trf = nfc_digital_get_drvdata(ddev);

        dev_dbg(trf->dev, "Unsupported interface\n");

        return -EINVAL;
}

static int trf7970a_tg_send_cmd(struct nfc_digital_dev *ddev,
                struct sk_buff *skb, u16 timeout,
                nfc_digital_cmd_complete_t cb, void *arg)
{
        struct trf7970a *trf = nfc_digital_get_drvdata(ddev);

        dev_dbg(trf->dev, "Unsupported interface\n");

        return -EINVAL;
}

static int trf7970a_tg_listen(struct nfc_digital_dev *ddev,
                u16 timeout, nfc_digital_cmd_complete_t cb, void *arg)
{
        struct trf7970a *trf = nfc_digital_get_drvdata(ddev);

        dev_dbg(trf->dev, "Unsupported interface\n");

        return -EINVAL;
}

static void trf7970a_abort_cmd(struct nfc_digital_dev *ddev)
{
        struct trf7970a *trf = nfc_digital_get_drvdata(ddev);

        dev_dbg(trf->dev, "Abort process initiated\n");

        mutex_lock(&trf->lock);

        switch (trf->state) {
        case TRF7970A_ST_WAIT_FOR_TX_FIFO:
        case TRF7970A_ST_WAIT_FOR_RX_DATA:
        case TRF7970A_ST_WAIT_FOR_RX_DATA_CONT:
        case TRF7970A_ST_WAIT_TO_ISSUE_EOF:
                trf->aborting = true;
                break;
        default:
                break;
        }

        mutex_unlock(&trf->lock);
}

static struct nfc_digital_ops trf7970a_nfc_ops = {
        .in_configure_hw        = trf7970a_in_configure_hw,
        .in_send_cmd            = trf7970a_in_send_cmd,
        .tg_configure_hw        = trf7970a_tg_configure_hw,
        .tg_send_cmd            = trf7970a_tg_send_cmd,
        .tg_listen              = trf7970a_tg_listen,
        .switch_rf              = trf7970a_switch_rf,
        .abort_cmd              = trf7970a_abort_cmd,
};

static int trf7970a_get_autosuspend_delay(struct device_node *np)
{
        int autosuspend_delay, ret;

        ret = of_property_read_u32(np, "autosuspend-delay", &autosuspend_delay);
        if (ret)
                autosuspend_delay = TRF7970A_AUTOSUSPEND_DELAY;

        return autosuspend_delay;
}

static int trf7970a_get_vin_voltage_override(struct device_node *np,
                u32 *vin_uvolts)
{
        return of_property_read_u32(np, "vin-voltage-override", vin_uvolts);
}

static int trf7970a_probe(struct spi_device *spi)
{
        struct device_node *np = spi->dev.of_node;
        struct trf7970a *trf;
        int uvolts, autosuspend_delay, ret;

        if (!np) {
                dev_err(&spi->dev, "No Device Tree entry\n");
                return -EINVAL;
        }

        trf = devm_kzalloc(&spi->dev, sizeof(*trf), GFP_KERNEL);
        if (!trf)
                return -ENOMEM;

        trf->state = TRF7970A_ST_OFF;
        trf->dev = &spi->dev;
        trf->spi = spi;

        spi->mode = SPI_MODE_1;
        spi->bits_per_word = 8;

        ret = spi_setup(spi);
        if (ret < 0) {
                dev_err(trf->dev, "Can't set up SPI Communication\n");
                return ret;
        }

        if (of_property_read_bool(np, "irq-status-read-quirk"))
                trf->quirks |= TRF7970A_QUIRK_IRQ_STATUS_READ;

        /* There are two enable pins - both must be present */
        trf->en_gpio = of_get_named_gpio(np, "ti,enable-gpios", 0);
        if (!gpio_is_valid(trf->en_gpio)) {
                dev_err(trf->dev, "No EN GPIO property\n");
                return trf->en_gpio;
        }

        ret = devm_gpio_request_one(trf->dev, trf->en_gpio,
                        GPIOF_DIR_OUT | GPIOF_INIT_LOW, "trf7970a EN");
        if (ret) {
                dev_err(trf->dev, "Can't request EN GPIO: %d\n", ret);
                return ret;
        }

        trf->en2_gpio = of_get_named_gpio(np, "ti,enable-gpios", 1);
        if (!gpio_is_valid(trf->en2_gpio)) {
                dev_err(trf->dev, "No EN2 GPIO property\n");
                return trf->en2_gpio;
        }

        ret = devm_gpio_request_one(trf->dev, trf->en2_gpio,
                        GPIOF_DIR_OUT | GPIOF_INIT_LOW, "trf7970a EN2");
        if (ret) {
                dev_err(trf->dev, "Can't request EN2 GPIO: %d\n", ret);
                return ret;
        }

        if (of_property_read_bool(np, "en2-rf-quirk"))
                trf->quirks |= TRF7970A_QUIRK_EN2_MUST_STAY_LOW;

        ret = devm_request_threaded_irq(trf->dev, spi->irq, NULL,
                        trf7970a_irq, IRQF_TRIGGER_RISING | IRQF_ONESHOT,
                        "trf7970a", trf);
        if (ret) {
                dev_err(trf->dev, "Can't request IRQ#%d: %d\n", spi->irq, ret);
                return ret;
        }

        mutex_init(&trf->lock);
        INIT_DELAYED_WORK(&trf->timeout_work, trf7970a_timeout_work_handler);

        trf->regulator = devm_regulator_get(&spi->dev, "vin");
        if (IS_ERR(trf->regulator)) {
                ret = PTR_ERR(trf->regulator);
                dev_err(trf->dev, "Can't get VIN regulator: %d\n", ret);
                goto err_destroy_lock;
        }

        ret = regulator_enable(trf->regulator);
        if (ret) {
                dev_err(trf->dev, "Can't enable VIN: %d\n", ret);
                goto err_destroy_lock;
        }

        ret = trf7970a_get_vin_voltage_override(np, &uvolts);
        if (ret)
                uvolts = regulator_get_voltage(trf->regulator);

        if (uvolts > 4000000)
                trf->chip_status_ctrl = TRF7970A_CHIP_STATUS_VRS5_3;

        trf->ddev = nfc_digital_allocate_device(&trf7970a_nfc_ops,
                        TRF7970A_SUPPORTED_PROTOCOLS,
                        NFC_DIGITAL_DRV_CAPS_IN_CRC, TRF7970A_TX_SKB_HEADROOM,
                        0);
        if (!trf->ddev) {
                dev_err(trf->dev, "Can't allocate NFC digital device\n");
                ret = -ENOMEM;
                goto err_disable_regulator;
        }

        nfc_digital_set_parent_dev(trf->ddev, trf->dev);
        nfc_digital_set_drvdata(trf->ddev, trf);
        spi_set_drvdata(spi, trf);

        autosuspend_delay = trf7970a_get_autosuspend_delay(np);

        pm_runtime_set_autosuspend_delay(trf->dev, autosuspend_delay);
        pm_runtime_use_autosuspend(trf->dev);
        pm_runtime_enable(trf->dev);

        ret = nfc_digital_register_device(trf->ddev);
        if (ret) {
                dev_err(trf->dev, "Can't register NFC digital device: %d\n",
                                ret);
                goto err_free_ddev;
        }

        return 0;

err_free_ddev:
        pm_runtime_disable(trf->dev);
        nfc_digital_free_device(trf->ddev);
err_disable_regulator:
        regulator_disable(trf->regulator);
err_destroy_lock:
        mutex_destroy(&trf->lock);
        return ret;
}

static int trf7970a_remove(struct spi_device *spi)
{
        struct trf7970a *trf = spi_get_drvdata(spi);

        mutex_lock(&trf->lock);

        switch (trf->state) {
        case TRF7970A_ST_WAIT_FOR_TX_FIFO:
        case TRF7970A_ST_WAIT_FOR_RX_DATA:
        case TRF7970A_ST_WAIT_FOR_RX_DATA_CONT:
        case TRF7970A_ST_WAIT_TO_ISSUE_EOF:
                trf7970a_send_err_upstream(trf, -ECANCELED);
                /* FALLTHROUGH */
        case TRF7970A_ST_IDLE:
        case TRF7970A_ST_IDLE_RX_BLOCKED:
                pm_runtime_put_sync(trf->dev);
                break;
        default:
                break;
        }

        mutex_unlock(&trf->lock);

        pm_runtime_disable(trf->dev);

        nfc_digital_unregister_device(trf->ddev);
        nfc_digital_free_device(trf->ddev);

        regulator_disable(trf->regulator);

        mutex_destroy(&trf->lock);

        return 0;
}

#ifdef CONFIG_PM_RUNTIME
static int trf7970a_pm_runtime_suspend(struct device *dev)
{
        struct spi_device *spi = container_of(dev, struct spi_device, dev);
        struct trf7970a *trf = spi_get_drvdata(spi);
        int ret;

        dev_dbg(dev, "Runtime suspend\n");

        if (trf->state != TRF7970A_ST_OFF) {
                dev_dbg(dev, "Can't suspend - not in OFF state (%d)\n",
                                trf->state);
                return -EBUSY;
        }

        gpio_set_value(trf->en_gpio, 0);
        gpio_set_value(trf->en2_gpio, 0);

        ret = regulator_disable(trf->regulator);
        if (ret)
                dev_err(dev, "%s - Can't disable VIN: %d\n", __func__, ret);

        return ret;
}

static int trf7970a_pm_runtime_resume(struct device *dev)
{
        struct spi_device *spi = container_of(dev, struct spi_device, dev);
        struct trf7970a *trf = spi_get_drvdata(spi);
        int ret;

        dev_dbg(dev, "Runtime resume\n");

        ret = regulator_enable(trf->regulator);
        if (ret) {
                dev_err(dev, "%s - Can't enable VIN: %d\n", __func__, ret);
                return ret;
        }

        usleep_range(5000, 6000);

        if (!(trf->quirks & TRF7970A_QUIRK_EN2_MUST_STAY_LOW)) {
                gpio_set_value(trf->en2_gpio, 1);
                usleep_range(1000, 2000);
        }

        gpio_set_value(trf->en_gpio, 1);

        usleep_range(20000, 21000);

        pm_runtime_mark_last_busy(dev);

        return 0;
}
#endif

static const struct dev_pm_ops trf7970a_pm_ops = {
        SET_RUNTIME_PM_OPS(trf7970a_pm_runtime_suspend,
                        trf7970a_pm_runtime_resume, NULL)
};

static const struct spi_device_id trf7970a_id_table[] = {
        { "trf7970a", 0 },
        { }
};
MODULE_DEVICE_TABLE(spi, trf7970a_id_table);

static struct spi_driver trf7970a_spi_driver = {
        .probe          = trf7970a_probe,
        .remove         = trf7970a_remove,
        .id_table       = trf7970a_id_table,
        .driver         = {
                .name   = "trf7970a",
                .owner  = THIS_MODULE,
                .pm     = &trf7970a_pm_ops,
        },
};

module_spi_driver(trf7970a_spi_driver);

MODULE_AUTHOR("Mark A. Greer <mgreer@animalcreek.com>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("TI trf7970a RFID/NFC Transceiver Driver");