drivers/mtd/devices/mchp23k256.c

   1 /*
   2  * mchp23k256.c
   3  *
   4  * Driver for Microchip 23k256 SPI RAM chips
   5  *
   6  * Copyright © 2016 Andrew Lunn <andrew@lunn.ch>
   7  *
   8  * This code is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  */
  13 #include <linux/device.h>
  14 #include <linux/module.h>
  15 #include <linux/mtd/mtd.h>
  16 #include <linux/mtd/partitions.h>
  17 #include <linux/mutex.h>
  18 #include <linux/sched.h>
  19 #include <linux/sizes.h>
  20 #include <linux/spi/flash.h>
  21 #include <linux/spi/spi.h>
  22 #include <linux/of_device.h>
  23
  24 #define MAX_CMD_SIZE            4
  25
  26 struct mchp23_caps {
  27         u8 addr_width;
  28         unsigned int size;
  29 };
  30
  31 struct mchp23k256_flash {
  32         struct spi_device       *spi;
  33         struct mutex            lock;
  34         struct mtd_info         mtd;
  35         const struct mchp23_caps        *caps;
  36 };
  37
  38 #define MCHP23K256_CMD_WRITE_STATUS     0x01
  39 #define MCHP23K256_CMD_WRITE            0x02
  40 #define MCHP23K256_CMD_READ             0x03
  41 #define MCHP23K256_MODE_SEQ             BIT(6)
  42
  43 #define to_mchp23k256_flash(x) container_of(x, struct mchp23k256_flash, mtd)
  44
  45 static void mchp23k256_addr2cmd(struct mchp23k256_flash *flash,
  46                                 unsigned int addr, u8 *cmd)
  47 {
  48         int i;
  49
  50         /*
  51          * Address is sent in big endian (MSB first) and we skip
  52          * the first entry of the cmd array which contains the cmd
  53          * opcode.
  54          */
  55         for (i = flash->caps->addr_width; i > 0; i--, addr >>= 8)
  56                 cmd[i] = addr;
  57 }
  58
  59 static int mchp23k256_cmdsz(struct mchp23k256_flash *flash)
  60 {
  61         return 1 + flash->caps->addr_width;
  62 }
  63
  64 static int mchp23k256_write(struct mtd_info *mtd, loff_t to, size_t len,
  65                             size_t *retlen, const unsigned char *buf)
  66 {
  67         struct mchp23k256_flash *flash = to_mchp23k256_flash(mtd);
  68         struct spi_transfer transfer[2] = {};
  69         struct spi_message message;
  70         unsigned char command[MAX_CMD_SIZE];
  71
  72         spi_message_init(&message);
  73
  74         command[0] = MCHP23K256_CMD_WRITE;
  75         mchp23k256_addr2cmd(flash, to, command);
  76
  77         transfer[0].tx_buf = command;
  78         transfer[0].len = mchp23k256_cmdsz(flash);
  79         spi_message_add_tail(&transfer[0], &message);
  80
  81         transfer[1].tx_buf = buf;
  82         transfer[1].len = len;
  83         spi_message_add_tail(&transfer[1], &message);
  84
  85         mutex_lock(&flash->lock);
  86
  87         spi_sync(flash->spi, &message);
  88
  89         if (retlen && message.actual_length > sizeof(command))
  90                 *retlen += message.actual_length - sizeof(command);
  91
  92         mutex_unlock(&flash->lock);
  93         return 0;
  94 }
  95
  96 static int mchp23k256_read(struct mtd_info *mtd, loff_t from, size_t len,
  97                            size_t *retlen, unsigned char *buf)
  98 {
  99         struct mchp23k256_flash *flash = to_mchp23k256_flash(mtd);
 100         struct spi_transfer transfer[2] = {};
 101         struct spi_message message;
 102         unsigned char command[MAX_CMD_SIZE];
 103
 104         spi_message_init(&message);
 105
 106         memset(&transfer, 0, sizeof(transfer));
 107         command[0] = MCHP23K256_CMD_READ;
 108         mchp23k256_addr2cmd(flash, from, command);
 109
 110         transfer[0].tx_buf = command;
 111         transfer[0].len = mchp23k256_cmdsz(flash);
 112         spi_message_add_tail(&transfer[0], &message);
 113
 114         transfer[1].rx_buf = buf;
 115         transfer[1].len = len;
 116         spi_message_add_tail(&transfer[1], &message);
 117
 118         mutex_lock(&flash->lock);
 119
 120         spi_sync(flash->spi, &message);
 121
 122         if (retlen && message.actual_length > sizeof(command))
 123                 *retlen += message.actual_length - sizeof(command);
 124
 125         mutex_unlock(&flash->lock);
 126         return 0;
 127 }
 128
 129 /*
 130  * Set the device into sequential mode. This allows read/writes to the
 131  * entire SRAM in a single operation
 132  */
 133 static int mchp23k256_set_mode(struct spi_device *spi)
 134 {
 135         struct spi_transfer transfer = {};
 136         struct spi_message message;
 137         unsigned char command[2];
 138
 139         spi_message_init(&message);
 140
 141         command[0] = MCHP23K256_CMD_WRITE_STATUS;
 142         command[1] = MCHP23K256_MODE_SEQ;
 143
 144         transfer.tx_buf = command;
 145         transfer.len = sizeof(command);
 146         spi_message_add_tail(&transfer, &message);
 147
 148         return spi_sync(spi, &message);
 149 }
 150
 151 static const struct mchp23_caps mchp23k256_caps = {
 152         .size = SZ_32K,
 153         .addr_width = 2,
 154 };
 155
 156 static const struct mchp23_caps mchp23lcv1024_caps = {
 157         .size = SZ_128K,
 158         .addr_width = 3,
 159 };
 160
 161 static int mchp23k256_probe(struct spi_device *spi)
 162 {
 163         struct mchp23k256_flash *flash;
 164         struct flash_platform_data *data;
 165         int err;
 166
 167         flash = devm_kzalloc(&spi->dev, sizeof(*flash), GFP_KERNEL);
 168         if (!flash)
 169                 return -ENOMEM;
 170
 171         flash->spi = spi;
 172         mutex_init(&flash->lock);
 173         spi_set_drvdata(spi, flash);
 174
 175         err = mchp23k256_set_mode(spi);
 176         if (err)
 177                 return err;
 178
 179         data = dev_get_platdata(&spi->dev);
 180
 181         flash->caps = of_device_get_match_data(&spi->dev);
 182         if (!flash->caps)
 183                 flash->caps = &mchp23k256_caps;
 184
 185         mtd_set_of_node(&flash->mtd, spi->dev.of_node);
 186         flash->mtd.dev.parent   = &spi->dev;
 187         flash->mtd.type         = MTD_RAM;
 188         flash->mtd.flags        = MTD_CAP_RAM;
 189         flash->mtd.writesize    = 1;
 190         flash->mtd.size         = flash->caps->size;
 191         flash->mtd._read        = mchp23k256_read;
 192         flash->mtd._write       = mchp23k256_write;
 193
 194         err = mtd_device_register(&flash->mtd, data ? data->parts : NULL,
 195                                   data ? data->nr_parts : 0);
 196         if (err)
 197                 return err;
 198
 199         return 0;
 200 }
 201
 202 static int mchp23k256_remove(struct spi_device *spi)
 203 {
 204         struct mchp23k256_flash *flash = spi_get_drvdata(spi);
 205
 206         return mtd_device_unregister(&flash->mtd);
 207 }
 208
 209 static const struct of_device_id mchp23k256_of_table[] = {
 210         {
 211                 .compatible = "microchip,mchp23k256",
 212                 .data = &mchp23k256_caps,
 213         },
 214         {
 215                 .compatible = "microchip,mchp23lcv1024",
 216                 .data = &mchp23lcv1024_caps,
 217         },
 218         {}
 219 };
 220 MODULE_DEVICE_TABLE(of, mchp23k256_of_table);
 221
 222 static struct spi_driver mchp23k256_driver = {
 223         .driver = {
 224                 .name   = "mchp23k256",
 225                 .of_match_table = of_match_ptr(mchp23k256_of_table),
 226         },
 227         .probe          = mchp23k256_probe,
 228         .remove         = mchp23k256_remove,
 229 };
 230
 231 module_spi_driver(mchp23k256_driver);
 232
 233 MODULE_DESCRIPTION("MTD SPI driver for MCHP23K256 RAM chips");
 234 MODULE_AUTHOR("Andrew Lunn <andre@lunn.ch>");
 235 MODULE_LICENSE("GPL v2");
 236 MODULE_ALIAS("spi:mchp23k256");