2 * 8250_dma.c - DMA Engine API support for 8250.c
4 * Copyright (C) 2013 Intel Corporation
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.
11 #include <linux/tty.h>
12 #include <linux/tty_flip.h>
13 #include <linux/serial_reg.h>
14 #include <linux/dma-mapping.h>
18 static void __dma_tx_complete(void *param)
20 struct uart_8250_port *p = param;
21 struct uart_8250_dma *dma = p->dma;
22 struct circ_buf *xmit = &p->port.state->xmit;
26 dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
27 UART_XMIT_SIZE, DMA_TO_DEVICE);
29 spin_lock_irqsave(&p->port.lock, flags);
33 xmit->tail += dma->tx_size;
34 xmit->tail &= UART_XMIT_SIZE - 1;
35 p->port.icount.tx += dma->tx_size;
37 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
38 uart_write_wakeup(&p->port);
40 ret = serial8250_tx_dma(p);
42 p->ier |= UART_IER_THRI;
43 serial_port_out(&p->port, UART_IER, p->ier);
46 spin_unlock_irqrestore(&p->port.lock, flags);
49 static void __dma_rx_complete(void *param)
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 enum dma_status dma_status;
59 * New DMA Rx can be started during the completion handler before it
60 * could acquire port's lock and it might still be ongoing. Don't to
61 * anything in such case.
63 dma_status = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
64 if (dma_status == DMA_IN_PROGRESS)
67 count = dma->rx_size - state.residue;
69 tty_insert_flip_string(tty_port, dma->rx_buf, count);
70 p->port.icount.rx += count;
73 tty_flip_buffer_push(tty_port);
76 static void dma_rx_complete(void *param)
78 struct uart_8250_port *p = param;
79 struct uart_8250_dma *dma = p->dma;
82 spin_lock_irqsave(&p->port.lock, flags);
85 spin_unlock_irqrestore(&p->port.lock, flags);
88 int serial8250_tx_dma(struct uart_8250_port *p)
90 struct uart_8250_dma *dma = p->dma;
91 struct circ_buf *xmit = &p->port.state->xmit;
92 struct dma_async_tx_descriptor *desc;
98 if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) {
99 /* We have been called from __dma_tx_complete() */
100 serial8250_rpm_put_tx(p);
104 dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
106 desc = dmaengine_prep_slave_single(dma->txchan,
107 dma->tx_addr + xmit->tail,
108 dma->tx_size, DMA_MEM_TO_DEV,
109 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
116 desc->callback = __dma_tx_complete;
117 desc->callback_param = p;
119 dma->tx_cookie = dmaengine_submit(desc);
121 dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
122 UART_XMIT_SIZE, DMA_TO_DEVICE);
124 dma_async_issue_pending(dma->txchan);
127 if (p->ier & UART_IER_THRI) {
128 p->ier &= ~UART_IER_THRI;
129 serial_out(p, UART_IER, p->ier);
138 int serial8250_rx_dma(struct uart_8250_port *p)
140 struct uart_8250_dma *dma = p->dma;
141 struct dma_async_tx_descriptor *desc;
146 desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
147 dma->rx_size, DMA_DEV_TO_MEM,
148 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
153 desc->callback = dma_rx_complete;
154 desc->callback_param = p;
156 dma->rx_cookie = dmaengine_submit(desc);
158 dma_async_issue_pending(dma->rxchan);
163 void serial8250_rx_dma_flush(struct uart_8250_port *p)
165 struct uart_8250_dma *dma = p->dma;
167 if (dma->rx_running) {
168 dmaengine_pause(dma->rxchan);
169 __dma_rx_complete(p);
170 dmaengine_terminate_async(dma->rxchan);
173 EXPORT_SYMBOL_GPL(serial8250_rx_dma_flush);
175 int serial8250_request_dma(struct uart_8250_port *p)
177 struct uart_8250_dma *dma = p->dma;
178 phys_addr_t rx_dma_addr = dma->rx_dma_addr ?
179 dma->rx_dma_addr : p->port.mapbase;
180 phys_addr_t tx_dma_addr = dma->tx_dma_addr ?
181 dma->tx_dma_addr : p->port.mapbase;
183 struct dma_slave_caps caps;
186 /* Default slave configuration parameters */
187 dma->rxconf.direction = DMA_DEV_TO_MEM;
188 dma->rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
189 dma->rxconf.src_addr = rx_dma_addr + UART_RX;
191 dma->txconf.direction = DMA_MEM_TO_DEV;
192 dma->txconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
193 dma->txconf.dst_addr = tx_dma_addr + UART_TX;
196 dma_cap_set(DMA_SLAVE, mask);
198 /* Get a channel for RX */
199 dma->rxchan = dma_request_slave_channel_compat(mask,
200 dma->fn, dma->rx_param,
205 /* 8250 rx dma requires dmaengine driver to support pause/terminate */
206 ret = dma_get_slave_caps(dma->rxchan, &caps);
209 if (!caps.cmd_pause || !caps.cmd_terminate ||
210 caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
215 dmaengine_slave_config(dma->rxchan, &dma->rxconf);
217 /* Get a channel for TX */
218 dma->txchan = dma_request_slave_channel_compat(mask,
219 dma->fn, dma->tx_param,
226 /* 8250 tx dma requires dmaengine driver to support terminate */
227 ret = dma_get_slave_caps(dma->txchan, &caps);
230 if (!caps.cmd_terminate) {
235 dmaengine_slave_config(dma->txchan, &dma->txconf);
239 dma->rx_size = PAGE_SIZE;
241 dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
242 &dma->rx_addr, GFP_KERNEL);
249 dma->tx_addr = dma_map_single(dma->txchan->device->dev,
250 p->port.state->xmit.buf,
253 if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) {
254 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size,
255 dma->rx_buf, dma->rx_addr);
260 dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
264 dma_release_channel(dma->txchan);
266 dma_release_channel(dma->rxchan);
269 EXPORT_SYMBOL_GPL(serial8250_request_dma);
271 void serial8250_release_dma(struct uart_8250_port *p)
273 struct uart_8250_dma *dma = p->dma;
278 /* Release RX resources */
279 dmaengine_terminate_sync(dma->rxchan);
280 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
282 dma_release_channel(dma->rxchan);
285 /* Release TX resources */
286 dmaengine_terminate_sync(dma->txchan);
287 dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
288 UART_XMIT_SIZE, DMA_TO_DEVICE);
289 dma_release_channel(dma->txchan);
293 dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
295 EXPORT_SYMBOL_GPL(serial8250_release_dma);