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
  24         dma->tx_running = 0;
  25
  26         dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
  27                                 UART_XMIT_SIZE, DMA_TO_DEVICE);
  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         if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port))
  37                 serial8250_tx_dma(p);
  38 }
  39
  40 static void __dma_rx_complete(void *param)
  41 {
  42         struct uart_8250_port   *p = param;
  43         struct uart_8250_dma    *dma = p->dma;
  44         struct tty_port         *tty_port = &p->port.state->port;
  45         struct dma_tx_state     state;
  46         int                     count;
  47
  48         dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
  49                                 dma->rx_size, DMA_FROM_DEVICE);
  50
  51         dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
  52         dmaengine_terminate_all(dma->rxchan);
  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
  68         if (uart_tx_stopped(&p->port) || dma->tx_running ||
  69             uart_circ_empty(xmit))
  70                 return 0;
  71
  72         dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
  73
  74         desc = dmaengine_prep_slave_single(dma->txchan,
  75                                            dma->tx_addr + xmit->tail,
  76                                            dma->tx_size, DMA_MEM_TO_DEV,
  77                                            DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
  78         if (!desc)
  79                 return -EBUSY;
  80
  81         dma->tx_running = 1;
  82
  83         desc->callback = __dma_tx_complete;
  84         desc->callback_param = p;
  85
  86         dma->tx_cookie = dmaengine_submit(desc);
  87
  88         dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
  89                                    UART_XMIT_SIZE, DMA_TO_DEVICE);
  90
  91         dma_async_issue_pending(dma->txchan);
  92
  93         return 0;
  94 }
  95 EXPORT_SYMBOL_GPL(serial8250_tx_dma);
  96
  97 int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
  98 {
  99         struct uart_8250_dma            *dma = p->dma;
 100         struct dma_async_tx_descriptor  *desc;
 101         struct dma_tx_state             state;
 102         int                             dma_status;
 103
 104         /*
 105          * If RCVR FIFO trigger level was not reached, complete the transfer and
 106          * let 8250.c copy the remaining data.
 107          */
 108         if ((iir & 0x3f) == UART_IIR_RX_TIMEOUT) {
 109                 dma_status = dmaengine_tx_status(dma->rxchan, dma->rx_cookie,
 110                                                 &state);
 111                 if (dma_status == DMA_IN_PROGRESS) {
 112                         dmaengine_pause(dma->rxchan);
 113                         __dma_rx_complete(p);
 114                 }
 115                 return -ETIMEDOUT;
 116         }
 117
 118         desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
 119                                            dma->rx_size, DMA_DEV_TO_MEM,
 120                                            DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 121         if (!desc)
 122                 return -EBUSY;
 123
 124         desc->callback = __dma_rx_complete;
 125         desc->callback_param = p;
 126
 127         dma->rx_cookie = dmaengine_submit(desc);
 128
 129         dma_sync_single_for_device(dma->rxchan->device->dev, dma->rx_addr,
 130                                    dma->rx_size, DMA_FROM_DEVICE);
 131
 132         dma_async_issue_pending(dma->rxchan);
 133
 134         return 0;
 135 }
 136 EXPORT_SYMBOL_GPL(serial8250_rx_dma);
 137
 138 int serial8250_request_dma(struct uart_8250_port *p)
 139 {
 140         struct uart_8250_dma    *dma = p->dma;
 141         dma_cap_mask_t          mask;
 142
 143         dma->rxconf.src_addr = p->port.mapbase + UART_RX;
 144         dma->txconf.dst_addr = p->port.mapbase + UART_TX;
 145
 146         dma_cap_zero(mask);
 147         dma_cap_set(DMA_SLAVE, mask);
 148
 149         /* Get a channel for RX */
 150         dma->rxchan = dma_request_channel(mask, dma->fn, dma->rx_param);
 151         if (!dma->rxchan)
 152                 return -ENODEV;
 153
 154         dmaengine_slave_config(dma->rxchan, &dma->rxconf);
 155
 156         /* Get a channel for TX */
 157         dma->txchan = dma_request_channel(mask, dma->fn, dma->tx_param);
 158         if (!dma->txchan) {
 159                 dma_release_channel(dma->rxchan);
 160                 return -ENODEV;
 161         }
 162
 163         dmaengine_slave_config(dma->txchan, &dma->txconf);
 164
 165         /* RX buffer */
 166         if (!dma->rx_size)
 167                 dma->rx_size = PAGE_SIZE;
 168
 169         dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
 170                                         &dma->rx_addr, GFP_KERNEL);
 171         if (!dma->rx_buf) {
 172                 dma_release_channel(dma->rxchan);
 173                 dma_release_channel(dma->txchan);
 174                 return -ENOMEM;
 175         }
 176
 177         /* TX buffer */
 178         dma->tx_addr = dma_map_single(dma->txchan->device->dev,
 179                                         p->port.state->xmit.buf,
 180                                         UART_XMIT_SIZE,
 181                                         DMA_TO_DEVICE);
 182
 183         dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
 184
 185         return 0;
 186 }
 187 EXPORT_SYMBOL_GPL(serial8250_request_dma);
 188
 189 void serial8250_release_dma(struct uart_8250_port *p)
 190 {
 191         struct uart_8250_dma *dma = p->dma;
 192
 193         if (!dma)
 194                 return;
 195
 196         /* Release RX resources */
 197         dmaengine_terminate_all(dma->rxchan);
 198         dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
 199                           dma->rx_addr);
 200         dma_release_channel(dma->rxchan);
 201         dma->rxchan = NULL;
 202
 203         /* Release TX resources */
 204         dmaengine_terminate_all(dma->txchan);
 205         dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
 206                          UART_XMIT_SIZE, DMA_TO_DEVICE);
 207         dma_release_channel(dma->txchan);
 208         dma->txchan = NULL;
 209         dma->tx_running = 0;
 210
 211         dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
 212 }
 213 EXPORT_SYMBOL_GPL(serial8250_release_dma);