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, unsigned int iir) 114 { 115 struct uart_8250_dma *dma = p->dma; 116 struct dma_async_tx_descriptor *desc; 117 118 switch (iir & 0x3f) { 119 case UART_IIR_RLSI: 120 /* 8250_core handles errors and break interrupts */ 121 return -EIO; 122 case UART_IIR_RX_TIMEOUT: 123 /* 124 * If RCVR FIFO trigger level was not reached, complete the 125 * transfer and let 8250_core copy the remaining data. 126 */ 127 if (dma->rx_running) { 128 dmaengine_pause(dma->rxchan); 129 __dma_rx_complete(p); 130 dmaengine_terminate_all(dma->rxchan); 131 } 132 return -ETIMEDOUT; 133 default: 134 break; 135 } 136 137 if (dma->rx_running) 138 return 0; 139 140 desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr, 141 dma->rx_size, DMA_DEV_TO_MEM, 142 DMA_PREP_INTERRUPT | DMA_CTRL_ACK); 143 if (!desc) 144 return -EBUSY; 145 146 dma->rx_running = 1; 147 desc->callback = __dma_rx_complete; 148 desc->callback_param = p; 149 150 dma->rx_cookie = dmaengine_submit(desc); 151 152 dma_async_issue_pending(dma->rxchan); 153 154 return 0; 155 } 156 157 int serial8250_request_dma(struct uart_8250_port *p) 158 { 159 struct uart_8250_dma *dma = p->dma; 160 dma_cap_mask_t mask; 161 162 /* Default slave configuration parameters */ 163 dma->rxconf.direction = DMA_DEV_TO_MEM; 164 dma->rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE; 165 dma->rxconf.src_addr = p->port.mapbase + UART_RX; 166 167 dma->txconf.direction = DMA_MEM_TO_DEV; 168 dma->txconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE; 169 dma->txconf.dst_addr = p->port.mapbase + UART_TX; 170 171 dma_cap_zero(mask); 172 dma_cap_set(DMA_SLAVE, mask); 173 174 /* Get a channel for RX */ 175 dma->rxchan = dma_request_slave_channel_compat(mask, 176 dma->fn, dma->rx_param, 177 p->port.dev, "rx"); 178 if (!dma->rxchan) 179 return -ENODEV; 180 181 dmaengine_slave_config(dma->rxchan, &dma->rxconf); 182 183 /* Get a channel for TX */ 184 dma->txchan = dma_request_slave_channel_compat(mask, 185 dma->fn, dma->tx_param, 186 p->port.dev, "tx"); 187 if (!dma->txchan) { 188 dma_release_channel(dma->rxchan); 189 return -ENODEV; 190 } 191 192 dmaengine_slave_config(dma->txchan, &dma->txconf); 193 194 /* RX buffer */ 195 if (!dma->rx_size) 196 dma->rx_size = PAGE_SIZE; 197 198 dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size, 199 &dma->rx_addr, GFP_KERNEL); 200 if (!dma->rx_buf) 201 goto err; 202 203 /* TX buffer */ 204 dma->tx_addr = dma_map_single(dma->txchan->device->dev, 205 p->port.state->xmit.buf, 206 UART_XMIT_SIZE, 207 DMA_TO_DEVICE); 208 if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) { 209 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, 210 dma->rx_buf, dma->rx_addr); 211 goto err; 212 } 213 214 dev_dbg_ratelimited(p->port.dev, "got both dma channels\n"); 215 216 return 0; 217 err: 218 dma_release_channel(dma->rxchan); 219 dma_release_channel(dma->txchan); 220 221 return -ENOMEM; 222 } 223 EXPORT_SYMBOL_GPL(serial8250_request_dma); 224 225 void serial8250_release_dma(struct uart_8250_port *p) 226 { 227 struct uart_8250_dma *dma = p->dma; 228 229 if (!dma) 230 return; 231 232 /* Release RX resources */ 233 dmaengine_terminate_all(dma->rxchan); 234 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf, 235 dma->rx_addr); 236 dma_release_channel(dma->rxchan); 237 dma->rxchan = NULL; 238 239 /* Release TX resources */ 240 dmaengine_terminate_all(dma->txchan); 241 dma_unmap_single(dma->txchan->device->dev, dma->tx_addr, 242 UART_XMIT_SIZE, DMA_TO_DEVICE); 243 dma_release_channel(dma->txchan); 244 dma->txchan = NULL; 245 dma->tx_running = 0; 246 247 dev_dbg_ratelimited(p->port.dev, "dma channels released\n"); 248 } 249 EXPORT_SYMBOL_GPL(serial8250_release_dma); 250