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

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * 8250_dma.c - DMA Engine API support for 8250.c
   4  *
   5  * Copyright (C) 2013 Intel Corporation
   6  */
   7 #include <linux/tty.h>
   8 #include <linux/tty_flip.h>
   9 #include <linux/serial_reg.h>
  10 #include <linux/dma-mapping.h>
  11
  12 #include "8250.h"
  13
  14 static void __dma_tx_complete(void *param)
  15 {
  16         struct uart_8250_port   *p = param;
  17         struct uart_8250_dma    *dma = p->dma;
  18         struct circ_buf         *xmit = &p->port.state->xmit;
  19         unsigned long   flags;
  20         int             ret;
  21
  22         dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
  23                                 UART_XMIT_SIZE, DMA_TO_DEVICE);
  24
  25         spin_lock_irqsave(&p->port.lock, flags);
  26
  27         dma->tx_running = 0;
  28
  29         xmit->tail += dma->tx_size;
  30         xmit->tail &= UART_XMIT_SIZE - 1;
  31         p->port.icount.tx += dma->tx_size;
  32
  33         if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
  34                 uart_write_wakeup(&p->port);
  35
  36         ret = serial8250_tx_dma(p);
  37         if (ret)
  38                 serial8250_set_THRI(p);
  39
  40         spin_unlock_irqrestore(&p->port.lock, flags);
  41 }
  42
  43 static void __dma_rx_complete(void *param)
  44 {
  45         struct uart_8250_port   *p = param;
  46         struct uart_8250_dma    *dma = p->dma;
  47         struct tty_port         *tty_port = &p->port.state->port;
  48         struct dma_tx_state     state;
  49         int                     count;
  50
  51         dma->rx_running = 0;
  52         dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
  53
  54         count = dma->rx_size - state.residue;
  55
  56         tty_insert_flip_string(tty_port, dma->rx_buf, count);
  57         p->port.icount.rx += count;
  58
  59         tty_flip_buffer_push(tty_port);
  60 }
  61
  62 int serial8250_tx_dma(struct uart_8250_port *p)
  63 {
  64         struct uart_8250_dma            *dma = p->dma;
  65         struct circ_buf                 *xmit = &p->port.state->xmit;
  66         struct dma_async_tx_descriptor  *desc;
  67         struct uart_port                *up = &p->port;
  68         int ret;
  69
  70         if (dma->tx_running) {
  71                 if (up->x_char) {
  72                         dmaengine_pause(dma->txchan);
  73                         uart_xchar_out(up, UART_TX);
  74                         dmaengine_resume(dma->txchan);
  75                 }
  76                 return 0;
  77         } else if (up->x_char) {
  78                 uart_xchar_out(up, UART_TX);
  79         }
  80
  81         if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) {
  82                 /* We have been called from __dma_tx_complete() */
  83                 serial8250_rpm_put_tx(p);
  84                 return 0;
  85         }
  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         desc->callback = __dma_tx_complete;
 100         desc->callback_param = p;
 101
 102         dma->tx_cookie = dmaengine_submit(desc);
 103
 104         dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
 105                                    UART_XMIT_SIZE, DMA_TO_DEVICE);
 106
 107         dma_async_issue_pending(dma->txchan);
 108         if (dma->tx_err) {
 109                 dma->tx_err = 0;
 110                 serial8250_clear_THRI(p);
 111         }
 112         return 0;
 113 err:
 114         dma->tx_err = 1;
 115         return ret;
 116 }
 117
 118 int serial8250_rx_dma(struct uart_8250_port *p)
 119 {
 120         struct uart_8250_dma            *dma = p->dma;
 121         struct dma_async_tx_descriptor  *desc;
 122
 123         if (dma->rx_running)
 124                 return 0;
 125
 126         desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
 127                                            dma->rx_size, DMA_DEV_TO_MEM,
 128                                            DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 129         if (!desc)
 130                 return -EBUSY;
 131
 132         dma->rx_running = 1;
 133         desc->callback = __dma_rx_complete;
 134         desc->callback_param = p;
 135
 136         dma->rx_cookie = dmaengine_submit(desc);
 137
 138         dma_async_issue_pending(dma->rxchan);
 139
 140         return 0;
 141 }
 142
 143 void serial8250_rx_dma_flush(struct uart_8250_port *p)
 144 {
 145         struct uart_8250_dma *dma = p->dma;
 146
 147         if (dma->rx_running) {
 148                 dmaengine_pause(dma->rxchan);
 149                 __dma_rx_complete(p);
 150                 dmaengine_terminate_async(dma->rxchan);
 151         }
 152 }
 153 EXPORT_SYMBOL_GPL(serial8250_rx_dma_flush);
 154
 155 int serial8250_request_dma(struct uart_8250_port *p)
 156 {
 157         struct uart_8250_dma    *dma = p->dma;
 158         phys_addr_t rx_dma_addr = dma->rx_dma_addr ?
 159                                   dma->rx_dma_addr : p->port.mapbase;
 160         phys_addr_t tx_dma_addr = dma->tx_dma_addr ?
 161                                   dma->tx_dma_addr : p->port.mapbase;
 162         dma_cap_mask_t          mask;
 163         struct dma_slave_caps   caps;
 164         int                     ret;
 165
 166         /* Default slave configuration parameters */
 167         dma->rxconf.direction           = DMA_DEV_TO_MEM;
 168         dma->rxconf.src_addr_width      = DMA_SLAVE_BUSWIDTH_1_BYTE;
 169         dma->rxconf.src_addr            = rx_dma_addr + UART_RX;
 170
 171         dma->txconf.direction           = DMA_MEM_TO_DEV;
 172         dma->txconf.dst_addr_width      = DMA_SLAVE_BUSWIDTH_1_BYTE;
 173         dma->txconf.dst_addr            = tx_dma_addr + UART_TX;
 174
 175         dma_cap_zero(mask);
 176         dma_cap_set(DMA_SLAVE, mask);
 177
 178         /* Get a channel for RX */
 179         dma->rxchan = dma_request_slave_channel_compat(mask,
 180                                                        dma->fn, dma->rx_param,
 181                                                        p->port.dev, "rx");
 182         if (!dma->rxchan)
 183                 return -ENODEV;
 184
 185         /* 8250 rx dma requires dmaengine driver to support pause/terminate */
 186         ret = dma_get_slave_caps(dma->rxchan, &caps);
 187         if (ret)
 188                 goto release_rx;
 189         if (!caps.cmd_pause || !caps.cmd_terminate ||
 190             caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
 191                 ret = -EINVAL;
 192                 goto release_rx;
 193         }
 194
 195         dmaengine_slave_config(dma->rxchan, &dma->rxconf);
 196
 197         /* Get a channel for TX */
 198         dma->txchan = dma_request_slave_channel_compat(mask,
 199                                                        dma->fn, dma->tx_param,
 200                                                        p->port.dev, "tx");
 201         if (!dma->txchan) {
 202                 ret = -ENODEV;
 203                 goto release_rx;
 204         }
 205
 206         /* 8250 tx dma requires dmaengine driver to support terminate */
 207         ret = dma_get_slave_caps(dma->txchan, &caps);
 208         if (ret)
 209                 goto err;
 210         if (!caps.cmd_terminate) {
 211                 ret = -EINVAL;
 212                 goto err;
 213         }
 214
 215         dmaengine_slave_config(dma->txchan, &dma->txconf);
 216
 217         /* RX buffer */
 218         if (!dma->rx_size)
 219                 dma->rx_size = PAGE_SIZE;
 220
 221         dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
 222                                         &dma->rx_addr, GFP_KERNEL);
 223         if (!dma->rx_buf) {
 224                 ret = -ENOMEM;
 225                 goto err;
 226         }
 227
 228         /* TX buffer */
 229         dma->tx_addr = dma_map_single(dma->txchan->device->dev,
 230                                         p->port.state->xmit.buf,
 231                                         UART_XMIT_SIZE,
 232                                         DMA_TO_DEVICE);
 233         if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) {
 234                 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size,
 235                                   dma->rx_buf, dma->rx_addr);
 236                 ret = -ENOMEM;
 237                 goto err;
 238         }
 239
 240         dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
 241
 242         return 0;
 243 err:
 244         dma_release_channel(dma->txchan);
 245 release_rx:
 246         dma_release_channel(dma->rxchan);
 247         return ret;
 248 }
 249 EXPORT_SYMBOL_GPL(serial8250_request_dma);
 250
 251 void serial8250_release_dma(struct uart_8250_port *p)
 252 {
 253         struct uart_8250_dma *dma = p->dma;
 254
 255         if (!dma)
 256                 return;
 257
 258         /* Release RX resources */
 259         dmaengine_terminate_sync(dma->rxchan);
 260         dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
 261                           dma->rx_addr);
 262         dma_release_channel(dma->rxchan);
 263         dma->rxchan = NULL;
 264
 265         /* Release TX resources */
 266         dmaengine_terminate_sync(dma->txchan);
 267         dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
 268                          UART_XMIT_SIZE, DMA_TO_DEVICE);
 269         dma_release_channel(dma->txchan);
 270         dma->txchan = NULL;
 271         dma->tx_running = 0;
 272
 273         dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
 274 }
 275 EXPORT_SYMBOL_GPL(serial8250_release_dma);