drivers/tty/serial/8250/8250_dma.c

   1 /*
   2  * 8250_dma.c - DMA Engine API support for 8250.c
   3  *
   4  * Copyright (C) 2013 Intel Corporation
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  */
  11 #include <linux/tty.h>
  12 #include <linux/tty_flip.h>
  13 #include <linux/serial_reg.h>
  14 #include <linux/dma-mapping.h>
  15
  16 #include "8250.h"
  17
  18 static void __dma_tx_complete(void *param)
  19 {
  20         struct uart_8250_port   *p = param;
  21         struct uart_8250_dma    *dma = p->dma;
  22         struct circ_buf         *xmit = &p->port.state->xmit;
  23         unsigned long   flags;
  24
  25         dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
  26                                 UART_XMIT_SIZE, DMA_TO_DEVICE);
  27
  28         spin_lock_irqsave(&p->port.lock, flags);
  29
  30         dma->tx_running = 0;
  31
  32         xmit->tail += dma->tx_size;
  33         xmit->tail &= UART_XMIT_SIZE - 1;
  34         p->port.icount.tx += dma->tx_size;
  35
  36         if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
  37                 uart_write_wakeup(&p->port);
  38
  39         if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port)) {
  40                 int ret;
  41
  42                 ret = serial8250_tx_dma(p);
  43                 if (ret) {
  44                         dma->tx_err = 1;
  45                         p->ier |= UART_IER_THRI;
  46                         serial_port_out(&p->port, UART_IER, p->ier);
  47                 }
  48         }
  49
  50         spin_unlock_irqrestore(&p->port.lock, flags);
  51 }
  52
  53 static void __dma_rx_complete(void *param)
  54 {
  55         struct uart_8250_port   *p = param;
  56         struct uart_8250_dma    *dma = p->dma;
  57         struct tty_port         *tty_port = &p->port.state->port;
  58         struct dma_tx_state     state;
  59         int                     count;
  60
  61         dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
  62                                 dma->rx_size, DMA_FROM_DEVICE);
  63
  64         dma->rx_running = 0;
  65         dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
  66         dmaengine_terminate_all(dma->rxchan);
  67
  68         count = dma->rx_size - state.residue;
  69
  70         tty_insert_flip_string(tty_port, dma->rx_buf, count);
  71         p->port.icount.rx += count;
  72
  73         tty_flip_buffer_push(tty_port);
  74 }
  75
  76 int serial8250_tx_dma(struct uart_8250_port *p)
  77 {
  78         struct uart_8250_dma            *dma = p->dma;
  79         struct circ_buf                 *xmit = &p->port.state->xmit;
  80         struct dma_async_tx_descriptor  *desc;
  81         int ret;
  82
  83         if (uart_tx_stopped(&p->port) || dma->tx_running ||
  84             uart_circ_empty(xmit))
  85                 return 0;
  86
  87         dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
  88
  89         desc = dmaengine_prep_slave_single(dma->txchan,
  90                                            dma->tx_addr + xmit->tail,
  91                                            dma->tx_size, DMA_MEM_TO_DEV,
  92                                            DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
  93         if (!desc) {
  94                 ret = -EBUSY;
  95                 goto err;
  96         }
  97
  98         dma->tx_running = 1;
  99
 100         desc->callback = __dma_tx_complete;
 101         desc->callback_param = p;
 102
 103         dma->tx_cookie = dmaengine_submit(desc);
 104
 105         dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
 106                                    UART_XMIT_SIZE, DMA_TO_DEVICE);
 107
 108         dma_async_issue_pending(dma->txchan);
 109         if (dma->tx_err) {
 110                 dma->tx_err = 0;
 111                 if (p->ier & UART_IER_THRI) {
 112                         p->ier &= ~UART_IER_THRI;
 113                         serial_out(p, UART_IER, p->ier);
 114                 }
 115         }
 116         return 0;
 117 err:
 118         dma->tx_err = 1;
 119         return ret;
 120 }
 121
 122 int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
 123 {
 124         struct uart_8250_dma            *dma = p->dma;
 125         struct dma_async_tx_descriptor  *desc;
 126
 127         switch (iir & 0x3f) {
 128         case UART_IIR_RLSI:
 129                 /* 8250_core handles errors and break interrupts */
 130                 return -EIO;
 131         case UART_IIR_RX_TIMEOUT:
 132                 /*
 133                  * If RCVR FIFO trigger level was not reached, complete the
 134                  * transfer and let 8250_core copy the remaining data.
 135                  */
 136                 if (dma->rx_running) {
 137                         dmaengine_pause(dma->rxchan);
 138                         __dma_rx_complete(p);
 139                 }
 140                 return -ETIMEDOUT;
 141         default:
 142                 break;
 143         }
 144
 145         if (dma->rx_running)
 146                 return 0;
 147
 148         desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
 149                                            dma->rx_size, DMA_DEV_TO_MEM,
 150                                            DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 151         if (!desc)
 152                 return -EBUSY;
 153
 154         dma->rx_running = 1;
 155         desc->callback = __dma_rx_complete;
 156         desc->callback_param = p;
 157
 158         dma->rx_cookie = dmaengine_submit(desc);
 159
 160         dma_sync_single_for_device(dma->rxchan->device->dev, dma->rx_addr,
 161                                    dma->rx_size, DMA_FROM_DEVICE);
 162
 163         dma_async_issue_pending(dma->rxchan);
 164
 165         return 0;
 166 }
 167
 168 int serial8250_request_dma(struct uart_8250_port *p)
 169 {
 170         struct uart_8250_dma    *dma = p->dma;
 171         dma_cap_mask_t          mask;
 172
 173         /* Default slave configuration parameters */
 174         dma->rxconf.direction           = DMA_DEV_TO_MEM;
 175         dma->rxconf.src_addr_width      = DMA_SLAVE_BUSWIDTH_1_BYTE;
 176         dma->rxconf.src_addr            = p->port.mapbase + UART_RX;
 177
 178         dma->txconf.direction           = DMA_MEM_TO_DEV;
 179         dma->txconf.dst_addr_width      = DMA_SLAVE_BUSWIDTH_1_BYTE;
 180         dma->txconf.dst_addr            = p->port.mapbase + UART_TX;
 181
 182         dma_cap_zero(mask);
 183         dma_cap_set(DMA_SLAVE, mask);
 184
 185         /* Get a channel for RX */
 186         dma->rxchan = dma_request_slave_channel_compat(mask,
 187                                                        dma->fn, dma->rx_param,
 188                                                        p->port.dev, "rx");
 189         if (!dma->rxchan)
 190                 return -ENODEV;
 191
 192         dmaengine_slave_config(dma->rxchan, &dma->rxconf);
 193
 194         /* Get a channel for TX */
 195         dma->txchan = dma_request_slave_channel_compat(mask,
 196                                                        dma->fn, dma->tx_param,
 197                                                        p->port.dev, "tx");
 198         if (!dma->txchan) {
 199                 dma_release_channel(dma->rxchan);
 200                 return -ENODEV;
 201         }
 202
 203         dmaengine_slave_config(dma->txchan, &dma->txconf);
 204
 205         /* RX buffer */
 206         if (!dma->rx_size)
 207                 dma->rx_size = PAGE_SIZE;
 208
 209         dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
 210                                         &dma->rx_addr, GFP_KERNEL);
 211         if (!dma->rx_buf)
 212                 goto err;
 213
 214         /* TX buffer */
 215         dma->tx_addr = dma_map_single(dma->txchan->device->dev,
 216                                         p->port.state->xmit.buf,
 217                                         UART_XMIT_SIZE,
 218                                         DMA_TO_DEVICE);
 219         if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) {
 220                 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size,
 221                                   dma->rx_buf, dma->rx_addr);
 222                 goto err;
 223         }
 224
 225         dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
 226
 227         return 0;
 228 err:
 229         dma_release_channel(dma->rxchan);
 230         dma_release_channel(dma->txchan);
 231
 232         return -ENOMEM;
 233 }
 234 EXPORT_SYMBOL_GPL(serial8250_request_dma);
 235
 236 void serial8250_release_dma(struct uart_8250_port *p)
 237 {
 238         struct uart_8250_dma *dma = p->dma;
 239
 240         if (!dma)
 241                 return;
 242
 243         /* Release RX resources */
 244         dmaengine_terminate_all(dma->rxchan);
 245         dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
 246                           dma->rx_addr);
 247         dma_release_channel(dma->rxchan);
 248         dma->rxchan = NULL;
 249
 250         /* Release TX resources */
 251         dmaengine_terminate_all(dma->txchan);
 252         dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
 253                          UART_XMIT_SIZE, DMA_TO_DEVICE);
 254         dma_release_channel(dma->txchan);
 255         dma->txchan = NULL;
 256         dma->tx_running = 0;
 257
 258         dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
 259 }
 260 EXPORT_SYMBOL_GPL(serial8250_release_dma);