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
14static void __dma_tx_complete(void *param)
15{
16 struct uart_8250_port *p = param;
17 struct uart_8250_dma *dma = p->dma;
18 struct tty_port *tport = &p->port.state->port;
19 unsigned long flags;
20 int ret;
21
22 dma_sync_single_for_cpu(dev: dma->txchan->device->dev, addr: dma->tx_addr,
23 UART_XMIT_SIZE, dir: DMA_TO_DEVICE);
24
25 uart_port_lock_irqsave(up: &p->port, flags: &flags);
26
27 dma->tx_running = 0;
28
29 uart_xmit_advance(up: &p->port, chars: dma->tx_size);
30
31 if (kfifo_len(&tport->xmit_fifo) < WAKEUP_CHARS)
32 uart_write_wakeup(port: &p->port);
33
34 ret = serial8250_tx_dma(p);
35 if (ret || !dma->tx_running)
36 serial8250_set_THRI(up: p);
37
38 uart_port_unlock_irqrestore(up: &p->port, flags);
39}
40
41static void __dma_rx_complete(struct uart_8250_port *p)
42{
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 enum dma_status dma_status;
47 int count;
48
49 /*
50 * New DMA Rx can be started during the completion handler before it
51 * could acquire port's lock and it might still be ongoing. Don't to
52 * anything in such case.
53 */
54 dma_status = dmaengine_tx_status(chan: dma->rxchan, cookie: dma->rx_cookie, state: &state);
55 if (dma_status == DMA_IN_PROGRESS)
56 return;
57
58 count = dma->rx_size - state.residue;
59
60 tty_insert_flip_string(port: tty_port, chars: dma->rx_buf, size: count);
61 p->port.icount.rx += count;
62 dma->rx_running = 0;
63
64 tty_flip_buffer_push(port: tty_port);
65}
66
67static void dma_rx_complete(void *param)
68{
69 struct uart_8250_port *p = param;
70 struct uart_8250_dma *dma = p->dma;
71 unsigned long flags;
72
73 uart_port_lock_irqsave(up: &p->port, flags: &flags);
74 if (dma->rx_running)
75 __dma_rx_complete(p);
76
77 /*
78 * Cannot be combined with the previous check because __dma_rx_complete()
79 * changes dma->rx_running.
80 */
81 if (!dma->rx_running && (serial_lsr_in(up: p) & UART_LSR_DR))
82 p->dma->rx_dma(p);
83 uart_port_unlock_irqrestore(up: &p->port, flags);
84}
85
86int serial8250_tx_dma(struct uart_8250_port *p)
87{
88 struct uart_8250_dma *dma = p->dma;
89 struct tty_port *tport = &p->port.state->port;
90 struct dma_async_tx_descriptor *desc;
91 struct uart_port *up = &p->port;
92 struct scatterlist *sg;
93 struct scatterlist sgl[2];
94 int i;
95 int ret;
96
97 if (dma->tx_running) {
98 if (up->x_char) {
99 dmaengine_pause(chan: dma->txchan);
100 uart_xchar_out(uport: up, UART_TX);
101 dmaengine_resume(chan: dma->txchan);
102 }
103 return 0;
104 } else if (up->x_char) {
105 uart_xchar_out(uport: up, UART_TX);
106 }
107
108 if (uart_tx_stopped(port: &p->port) || kfifo_is_empty(&tport->xmit_fifo)) {
109 /* We have been called from __dma_tx_complete() */
110 return 0;
111 }
112
113 serial8250_do_prepare_tx_dma(p);
114
115 sg_init_table(sgl, ARRAY_SIZE(sgl));
116
117 ret = kfifo_dma_out_prepare_mapped(&tport->xmit_fifo, sgl, ARRAY_SIZE(sgl),
118 UART_XMIT_SIZE, dma->tx_addr);
119
120 dma->tx_size = 0;
121
122 for_each_sg(sgl, sg, ret, i)
123 dma->tx_size += sg_dma_len(sg);
124
125 desc = dmaengine_prep_slave_sg(chan: dma->txchan, sgl, sg_len: ret,
126 dir: DMA_MEM_TO_DEV,
127 flags: DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
128 if (!desc) {
129 ret = -EBUSY;
130 goto err;
131 }
132
133 dma->tx_running = 1;
134 desc->callback = __dma_tx_complete;
135 desc->callback_param = p;
136
137 dma->tx_cookie = dmaengine_submit(desc);
138
139 dma_sync_single_for_device(dev: dma->txchan->device->dev, addr: dma->tx_addr,
140 UART_XMIT_SIZE, dir: DMA_TO_DEVICE);
141
142 dma_async_issue_pending(chan: dma->txchan);
143 serial8250_clear_THRI(up: p);
144 dma->tx_err = 0;
145
146 return 0;
147err:
148 dma->tx_err = 1;
149 return ret;
150}
151
152void serial8250_tx_dma_flush(struct uart_8250_port *p)
153{
154 struct uart_8250_dma *dma = p->dma;
155
156 if (!dma->tx_running)
157 return;
158
159 /*
160 * kfifo_reset() has been called by the serial core, avoid
161 * advancing and underflowing in __dma_tx_complete().
162 */
163 dma->tx_size = 0;
164
165 dmaengine_terminate_async(chan: dma->txchan);
166}
167
168int serial8250_rx_dma(struct uart_8250_port *p)
169{
170 struct uart_8250_dma *dma = p->dma;
171 struct dma_async_tx_descriptor *desc;
172
173 if (dma->rx_running)
174 return 0;
175
176 serial8250_do_prepare_rx_dma(p);
177
178 desc = dmaengine_prep_slave_single(chan: dma->rxchan, buf: dma->rx_addr,
179 len: dma->rx_size, dir: DMA_DEV_TO_MEM,
180 flags: DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
181 if (!desc)
182 return -EBUSY;
183
184 dma->rx_running = 1;
185 desc->callback = dma_rx_complete;
186 desc->callback_param = p;
187
188 dma->rx_cookie = dmaengine_submit(desc);
189
190 dma_async_issue_pending(chan: dma->rxchan);
191
192 return 0;
193}
194
195void serial8250_rx_dma_flush(struct uart_8250_port *p)
196{
197 struct uart_8250_dma *dma = p->dma;
198
199 if (dma->rx_running) {
200 dmaengine_pause(chan: dma->rxchan);
201 __dma_rx_complete(p);
202 dmaengine_terminate_async(chan: dma->rxchan);
203 }
204}
205EXPORT_SYMBOL_GPL(serial8250_rx_dma_flush);
206
207int serial8250_request_dma(struct uart_8250_port *p)
208{
209 struct uart_8250_dma *dma = p->dma;
210 phys_addr_t rx_dma_addr = dma->rx_dma_addr ?
211 dma->rx_dma_addr : p->port.mapbase;
212 phys_addr_t tx_dma_addr = dma->tx_dma_addr ?
213 dma->tx_dma_addr : p->port.mapbase;
214 dma_cap_mask_t mask;
215 struct dma_slave_caps caps;
216 int ret;
217
218 /* Default slave configuration parameters */
219 dma->rxconf.direction = DMA_DEV_TO_MEM;
220 dma->rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
221 dma->rxconf.src_addr = rx_dma_addr + UART_RX;
222
223 dma->txconf.direction = DMA_MEM_TO_DEV;
224 dma->txconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
225 dma->txconf.dst_addr = tx_dma_addr + UART_TX;
226
227 dma_cap_zero(mask);
228 dma_cap_set(DMA_SLAVE, mask);
229
230 /* Get a channel for RX */
231 dma->rxchan = dma_request_slave_channel_compat(mask,
232 fn: dma->fn, fn_param: dma->rx_param,
233 dev: p->port.dev, name: "rx");
234 if (!dma->rxchan)
235 return -ENODEV;
236
237 /* 8250 rx dma requires dmaengine driver to support pause/terminate */
238 ret = dma_get_slave_caps(chan: dma->rxchan, caps: &caps);
239 if (ret)
240 goto release_rx;
241 if (!caps.cmd_pause || !caps.cmd_terminate ||
242 caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
243 ret = -EINVAL;
244 goto release_rx;
245 }
246
247 dmaengine_slave_config(chan: dma->rxchan, config: &dma->rxconf);
248
249 /* Get a channel for TX */
250 dma->txchan = dma_request_slave_channel_compat(mask,
251 fn: dma->fn, fn_param: dma->tx_param,
252 dev: p->port.dev, name: "tx");
253 if (!dma->txchan) {
254 ret = -ENODEV;
255 goto release_rx;
256 }
257
258 /* 8250 tx dma requires dmaengine driver to support terminate */
259 ret = dma_get_slave_caps(chan: dma->txchan, caps: &caps);
260 if (ret)
261 goto err;
262 if (!caps.cmd_terminate) {
263 ret = -EINVAL;
264 goto err;
265 }
266
267 dmaengine_slave_config(chan: dma->txchan, config: &dma->txconf);
268
269 /* RX buffer */
270 if (!dma->rx_size)
271 dma->rx_size = PAGE_SIZE;
272
273 dma->rx_buf = dma_alloc_coherent(dev: dma->rxchan->device->dev, size: dma->rx_size,
274 dma_handle: &dma->rx_addr, GFP_KERNEL);
275 if (!dma->rx_buf) {
276 ret = -ENOMEM;
277 goto err;
278 }
279
280 /* TX buffer */
281 dma->tx_addr = dma_map_single(dma->txchan->device->dev,
282 p->port.state->port.xmit_buf,
283 UART_XMIT_SIZE,
284 DMA_TO_DEVICE);
285 if (dma_mapping_error(dev: dma->txchan->device->dev, dma_addr: dma->tx_addr)) {
286 dma_free_coherent(dev: dma->rxchan->device->dev, size: dma->rx_size,
287 cpu_addr: dma->rx_buf, dma_handle: dma->rx_addr);
288 ret = -ENOMEM;
289 goto err;
290 }
291
292 dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
293
294 return 0;
295err:
296 dma_release_channel(chan: dma->txchan);
297release_rx:
298 dma_release_channel(chan: dma->rxchan);
299 return ret;
300}
301EXPORT_SYMBOL_GPL(serial8250_request_dma);
302
303void serial8250_release_dma(struct uart_8250_port *p)
304{
305 struct uart_8250_dma *dma = p->dma;
306
307 if (!dma)
308 return;
309
310 /* Release RX resources */
311 dmaengine_terminate_sync(chan: dma->rxchan);
312 dma_free_coherent(dev: dma->rxchan->device->dev, size: dma->rx_size, cpu_addr: dma->rx_buf,
313 dma_handle: dma->rx_addr);
314 dma_release_channel(chan: dma->rxchan);
315 dma->rxchan = NULL;
316
317 /* Release TX resources */
318 dmaengine_terminate_sync(chan: dma->txchan);
319 dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
320 UART_XMIT_SIZE, DMA_TO_DEVICE);
321 dma_release_channel(chan: dma->txchan);
322 dma->txchan = NULL;
323 dma->tx_running = 0;
324
325 dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
326}
327EXPORT_SYMBOL_GPL(serial8250_release_dma);
328

source code of linux/drivers/tty/serial/8250/8250_dma.c