summaryrefslogtreecommitdiff
path: root/drivers/tty/serial/8250/8250_dma.c
blob: 7fa66501792dd8043304af153ae9072ff287ce8c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
// SPDX-License-Identifier: GPL-2.0+
/*
 * 8250_dma.c - DMA Engine API support for 8250.c
 *
 * Copyright (C) 2013 Intel Corporation
 */
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_reg.h>
#include <linux/dma-mapping.h>

#include "8250.h"

static void __dma_tx_complete(void *param)
{
	struct uart_8250_port	*p = param;
	struct uart_8250_dma	*dma = p->dma;
	struct circ_buf		*xmit = &p->port.state->xmit;
	unsigned long	flags;
	int		ret;

	dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
				UART_XMIT_SIZE, DMA_TO_DEVICE);

	spin_lock_irqsave(&p->port.lock, flags);

	dma->tx_running = 0;

	uart_xmit_advance(&p->port, dma->tx_size);

	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
		uart_write_wakeup(&p->port);

	ret = serial8250_tx_dma(p);
	if (ret || !dma->tx_running)
		serial8250_set_THRI(p);

	spin_unlock_irqrestore(&p->port.lock, flags);
}

static void __dma_rx_complete(struct uart_8250_port *p)
{
	struct uart_8250_dma	*dma = p->dma;
	struct tty_port		*tty_port = &p->port.state->port;
	struct dma_tx_state	state;
	enum dma_status		dma_status;
	int			count;

	/*
	 * New DMA Rx can be started during the completion handler before it
	 * could acquire port's lock and it might still be ongoing. Don't to
	 * anything in such case.
	 */
	dma_status = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
	if (dma_status == DMA_IN_PROGRESS)
		return;

	count = dma->rx_size - state.residue;

	tty_insert_flip_string(tty_port, dma->rx_buf, count);
	p->port.icount.rx += count;
	dma->rx_running = 0;

	tty_flip_buffer_push(tty_port);
}

static void dma_rx_complete(void *param)
{
	struct uart_8250_port *p = param;
	struct uart_8250_dma *dma = p->dma;
	unsigned long flags;

	spin_lock_irqsave(&p->port.lock, flags);
	if (dma->rx_running)
		__dma_rx_complete(p);

	/*
	 * Cannot be combined with the previous check because __dma_rx_complete()
	 * changes dma->rx_running.
	 */
	if (!dma->rx_running && (serial_lsr_in(p) & UART_LSR_DR))
		p->dma->rx_dma(p);
	spin_unlock_irqrestore(&p->port.lock, flags);
}

int serial8250_tx_dma(struct uart_8250_port *p)
{
	struct uart_8250_dma		*dma = p->dma;
	struct circ_buf			*xmit = &p->port.state->xmit;
	struct dma_async_tx_descriptor	*desc;
	struct uart_port		*up = &p->port;
	int ret;

	if (dma->tx_running) {
		if (up->x_char) {
			dmaengine_pause(dma->txchan);
			uart_xchar_out(up, UART_TX);
			dmaengine_resume(dma->txchan);
		}
		return 0;
	} else if (up->x_char) {
		uart_xchar_out(up, UART_TX);
	}

	if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) {
		/* We have been called from __dma_tx_complete() */
		return 0;
	}

	dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);

	serial8250_do_prepare_tx_dma(p);

	desc = dmaengine_prep_slave_single(dma->txchan,
					   dma->tx_addr + xmit->tail,
					   dma->tx_size, DMA_MEM_TO_DEV,
					   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
	if (!desc) {
		ret = -EBUSY;
		goto err;
	}

	dma->tx_running = 1;
	desc->callback = __dma_tx_complete;
	desc->callback_param = p;

	dma->tx_cookie = dmaengine_submit(desc);

	dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
				   UART_XMIT_SIZE, DMA_TO_DEVICE);

	dma_async_issue_pending(dma->txchan);
	serial8250_clear_THRI(p);
	dma->tx_err = 0;

	return 0;
err:
	dma->tx_err = 1;
	return ret;
}

int serial8250_rx_dma(struct uart_8250_port *p)
{
	struct uart_8250_dma		*dma = p->dma;
	struct dma_async_tx_descriptor	*desc;

	if (dma->rx_running)
		return 0;

	serial8250_do_prepare_rx_dma(p);

	desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
					   dma->rx_size, DMA_DEV_TO_MEM,
					   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
	if (!desc)
		return -EBUSY;

	dma->rx_running = 1;
	desc->callback = dma_rx_complete;
	desc->callback_param = p;

	dma->rx_cookie = dmaengine_submit(desc);

	dma_async_issue_pending(dma->rxchan);

	return 0;
}

void serial8250_rx_dma_flush(struct uart_8250_port *p)
{
	struct uart_8250_dma *dma = p->dma;

	if (dma->rx_running) {
		dmaengine_pause(dma->rxchan);
		__dma_rx_complete(p);
		dmaengine_terminate_async(dma->rxchan);
	}
}
EXPORT_SYMBOL_GPL(serial8250_rx_dma_flush);

int serial8250_request_dma(struct uart_8250_port *p)
{
	struct uart_8250_dma	*dma = p->dma;
	phys_addr_t rx_dma_addr = dma->rx_dma_addr ?
				  dma->rx_dma_addr : p->port.mapbase;
	phys_addr_t tx_dma_addr = dma->tx_dma_addr ?
				  dma->tx_dma_addr : p->port.mapbase;
	dma_cap_mask_t		mask;
	struct dma_slave_caps	caps;
	int			ret;

	/* Default slave configuration parameters */
	dma->rxconf.direction		= DMA_DEV_TO_MEM;
	dma->rxconf.src_addr_width	= DMA_SLAVE_BUSWIDTH_1_BYTE;
	dma->rxconf.src_addr		= rx_dma_addr + UART_RX;

	dma->txconf.direction		= DMA_MEM_TO_DEV;
	dma->txconf.dst_addr_width	= DMA_SLAVE_BUSWIDTH_1_BYTE;
	dma->txconf.dst_addr		= tx_dma_addr + UART_TX;

	dma_cap_zero(mask);
	dma_cap_set(DMA_SLAVE, mask);

	/* Get a channel for RX */
	dma->rxchan = dma_request_slave_channel_compat(mask,
						       dma->fn, dma->rx_param,
						       p->port.dev, "rx");
	if (!dma->rxchan)
		return -ENODEV;

	/* 8250 rx dma requires dmaengine driver to support pause/terminate */
	ret = dma_get_slave_caps(dma->rxchan, &caps);
	if (ret)
		goto release_rx;
	if (!caps.cmd_pause || !caps.cmd_terminate ||
	    caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
		ret = -EINVAL;
		goto release_rx;
	}

	dmaengine_slave_config(dma->rxchan, &dma->rxconf);

	/* Get a channel for TX */
	dma->txchan = dma_request_slave_channel_compat(mask,
						       dma->fn, dma->tx_param,
						       p->port.dev, "tx");
	if (!dma->txchan) {
		ret = -ENODEV;
		goto release_rx;
	}

	/* 8250 tx dma requires dmaengine driver to support terminate */
	ret = dma_get_slave_caps(dma->txchan, &caps);
	if (ret)
		goto err;
	if (!caps.cmd_terminate) {
		ret = -EINVAL;
		goto err;
	}

	dmaengine_slave_config(dma->txchan, &dma->txconf);

	/* RX buffer */
	if (!dma->rx_size)
		dma->rx_size = PAGE_SIZE;

	dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
					&dma->rx_addr, GFP_KERNEL);
	if (!dma->rx_buf) {
		ret = -ENOMEM;
		goto err;
	}

	/* TX buffer */
	dma->tx_addr = dma_map_single(dma->txchan->device->dev,
					p->port.state->xmit.buf,
					UART_XMIT_SIZE,
					DMA_TO_DEVICE);
	if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) {
		dma_free_coherent(dma->rxchan->device->dev, dma->rx_size,
				  dma->rx_buf, dma->rx_addr);
		ret = -ENOMEM;
		goto err;
	}

	dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");

	return 0;
err:
	dma_release_channel(dma->txchan);
release_rx:
	dma_release_channel(dma->rxchan);
	return ret;
}
EXPORT_SYMBOL_GPL(serial8250_request_dma);

void serial8250_release_dma(struct uart_8250_port *p)
{
	struct uart_8250_dma *dma = p->dma;

	if (!dma)
		return;

	/* Release RX resources */
	dmaengine_terminate_sync(dma->rxchan);
	dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
			  dma->rx_addr);
	dma_release_channel(dma->rxchan);
	dma->rxchan = NULL;

	/* Release TX resources */
	dmaengine_terminate_sync(dma->txchan);
	dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
			 UART_XMIT_SIZE, DMA_TO_DEVICE);
	dma_release_channel(dma->txchan);
	dma->txchan = NULL;
	dma->tx_running = 0;

	dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
}
EXPORT_SYMBOL_GPL(serial8250_release_dma);