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 int ret; 25 26 dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr, 27 UART_XMIT_SIZE, DMA_TO_DEVICE); 28 29 spin_lock_irqsave(&p->port.lock, flags); 30 31 dma->tx_running = 0; 32 33 xmit->tail += dma->tx_size; 34 xmit->tail &= UART_XMIT_SIZE - 1; 35 p->port.icount.tx += dma->tx_size; 36 37 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) 38 uart_write_wakeup(&p->port); 39 40 ret = serial8250_tx_dma(p); 41 if (ret) { 42 p->ier |= UART_IER_THRI; 43 serial_port_out(&p->port, UART_IER, p->ier); 44 } 45 46 spin_unlock_irqrestore(&p->port.lock, flags); 47 } 48 49 static void __dma_rx_complete(void *param) 50 { 51 struct uart_8250_port *p = param; 52 struct uart_8250_dma *dma = p->dma; 53 struct tty_port *tty_port = &p->port.state->port; 54 struct dma_tx_state state; 55 int count; 56 57 dma->rx_running = 0; 58 dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state); 59 60 count = dma->rx_size - state.residue; 61 62 tty_insert_flip_string(tty_port, dma->rx_buf, count); 63 p->port.icount.rx += count; 64 65 tty_flip_buffer_push(tty_port); 66 } 67 68 int serial8250_tx_dma(struct uart_8250_port *p) 69 { 70 struct uart_8250_dma *dma = p->dma; 71 struct circ_buf *xmit = &p->port.state->xmit; 72 struct dma_async_tx_descriptor *desc; 73 int ret; 74 75 if (uart_tx_stopped(&p->port) || dma->tx_running || 76 uart_circ_empty(xmit)) 77 return 0; 78 79 dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE); 80 81 desc = dmaengine_prep_slave_single(dma->txchan, 82 dma->tx_addr + xmit->tail, 83 dma->tx_size, DMA_MEM_TO_DEV, 84 DMA_PREP_INTERRUPT | DMA_CTRL_ACK); 85 if (!desc) { 86 ret = -EBUSY; 87 goto err; 88 } 89 90 dma->tx_running = 1; 91 desc->callback = __dma_tx_complete; 92 desc->callback_param = p; 93 94 dma->tx_cookie = dmaengine_submit(desc); 95 96 dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr, 97 UART_XMIT_SIZE, DMA_TO_DEVICE); 98 99 dma_async_issue_pending(dma->txchan); 100 if (dma->tx_err) { 101 dma->tx_err = 0; 102 if (p->ier & UART_IER_THRI) { 103 p->ier &= ~UART_IER_THRI; 104 serial_out(p, UART_IER, p->ier); 105 } 106 } 107 return 0; 108 err: 109 dma->tx_err = 1; 110 return ret; 111 } 112 113 int serial8250_rx_dma(struct uart_8250_port *p) 114 { 115 struct uart_8250_dma *dma = p->dma; 116 struct dma_async_tx_descriptor *desc; 117 118 if (dma->rx_running) 119 return 0; 120 121 desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr, 122 dma->rx_size, DMA_DEV_TO_MEM, 123 DMA_PREP_INTERRUPT | DMA_CTRL_ACK); 124 if (!desc) 125 return -EBUSY; 126 127 dma->rx_running = 1; 128 desc->callback = __dma_rx_complete; 129 desc->callback_param = p; 130 131 dma->rx_cookie = dmaengine_submit(desc); 132 133 dma_async_issue_pending(dma->rxchan); 134 135 return 0; 136 } 137 138 void serial8250_rx_dma_flush(struct uart_8250_port *p) 139 { 140 struct uart_8250_dma *dma = p->dma; 141 142 if (dma->rx_running) { 143 dmaengine_pause(dma->rxchan); 144 __dma_rx_complete(p); 145 dmaengine_terminate_all(dma->rxchan); 146 } 147 } 148 149 int serial8250_request_dma(struct uart_8250_port *p) 150 { 151 struct uart_8250_dma *dma = p->dma; 152 dma_cap_mask_t mask; 153 struct dma_slave_caps caps; 154 int ret; 155 156 /* Default slave configuration parameters */ 157 dma->rxconf.direction = DMA_DEV_TO_MEM; 158 dma->rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE; 159 dma->rxconf.src_addr = p->port.mapbase + UART_RX; 160 161 dma->txconf.direction = DMA_MEM_TO_DEV; 162 dma->txconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE; 163 dma->txconf.dst_addr = p->port.mapbase + UART_TX; 164 165 dma_cap_zero(mask); 166 dma_cap_set(DMA_SLAVE, mask); 167 168 /* Get a channel for RX */ 169 dma->rxchan = dma_request_slave_channel_compat(mask, 170 dma->fn, dma->rx_param, 171 p->port.dev, "rx"); 172 if (!dma->rxchan) 173 return -ENODEV; 174 175 /* 8250 rx dma requires dmaengine driver to support pause/terminate */ 176 ret = dma_get_slave_caps(dma->rxchan, &caps); 177 if (ret) 178 goto release_rx; 179 if (!caps.cmd_pause || !caps.cmd_terminate || 180 caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) { 181 ret = -EINVAL; 182 goto release_rx; 183 } 184 185 dmaengine_slave_config(dma->rxchan, &dma->rxconf); 186 187 /* Get a channel for TX */ 188 dma->txchan = dma_request_slave_channel_compat(mask, 189 dma->fn, dma->tx_param, 190 p->port.dev, "tx"); 191 if (!dma->txchan) { 192 ret = -ENODEV; 193 goto release_rx; 194 } 195 196 /* 8250 tx dma requires dmaengine driver to support terminate */ 197 ret = dma_get_slave_caps(dma->txchan, &caps); 198 if (ret) 199 goto err; 200 if (!caps.cmd_terminate) { 201 ret = -EINVAL; 202 goto err; 203 } 204 205 dmaengine_slave_config(dma->txchan, &dma->txconf); 206 207 /* RX buffer */ 208 if (!dma->rx_size) 209 dma->rx_size = PAGE_SIZE; 210 211 dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size, 212 &dma->rx_addr, GFP_KERNEL); 213 if (!dma->rx_buf) { 214 ret = -ENOMEM; 215 goto err; 216 } 217 218 /* TX buffer */ 219 dma->tx_addr = dma_map_single(dma->txchan->device->dev, 220 p->port.state->xmit.buf, 221 UART_XMIT_SIZE, 222 DMA_TO_DEVICE); 223 if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) { 224 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, 225 dma->rx_buf, dma->rx_addr); 226 ret = -ENOMEM; 227 goto err; 228 } 229 230 dev_dbg_ratelimited(p->port.dev, "got both dma channels\n"); 231 232 return 0; 233 err: 234 dma_release_channel(dma->txchan); 235 release_rx: 236 dma_release_channel(dma->rxchan); 237 return ret; 238 } 239 EXPORT_SYMBOL_GPL(serial8250_request_dma); 240 241 void serial8250_release_dma(struct uart_8250_port *p) 242 { 243 struct uart_8250_dma *dma = p->dma; 244 245 if (!dma) 246 return; 247 248 /* Release RX resources */ 249 dmaengine_terminate_all(dma->rxchan); 250 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf, 251 dma->rx_addr); 252 dma_release_channel(dma->rxchan); 253 dma->rxchan = NULL; 254 255 /* Release TX resources */ 256 dmaengine_terminate_all(dma->txchan); 257 dma_unmap_single(dma->txchan->device->dev, dma->tx_addr, 258 UART_XMIT_SIZE, DMA_TO_DEVICE); 259 dma_release_channel(dma->txchan); 260 dma->txchan = NULL; 261 dma->tx_running = 0; 262 263 dev_dbg_ratelimited(p->port.dev, "dma channels released\n"); 264 } 265 EXPORT_SYMBOL_GPL(serial8250_release_dma); 266