1 // SPDX-License-Identifier: GPL-2.0+
3 * 8250_dma.c - DMA Engine API support for 8250.c
5 * Copyright (C) 2013 Intel Corporation
8 #include <linux/tty_flip.h>
9 #include <linux/serial_reg.h>
10 #include <linux/dma-mapping.h>
14 static void __dma_tx_complete(void *param)
16 struct uart_8250_port *p = param;
17 struct uart_8250_dma *dma = p->dma;
18 struct circ_buf *xmit = &p->port.state->xmit;
22 dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
23 UART_XMIT_SIZE, DMA_TO_DEVICE);
25 spin_lock_irqsave(&p->port.lock, flags);
29 xmit->tail += dma->tx_size;
30 xmit->tail &= UART_XMIT_SIZE - 1;
31 p->port.icount.tx += dma->tx_size;
33 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
34 uart_write_wakeup(&p->port);
36 ret = serial8250_tx_dma(p);
37 if (ret || !dma->tx_running)
38 serial8250_set_THRI(p);
40 spin_unlock_irqrestore(&p->port.lock, flags);
43 static void __dma_rx_complete(void *param)
45 struct uart_8250_port *p = param;
46 struct uart_8250_dma *dma = p->dma;
47 struct tty_port *tty_port = &p->port.state->port;
48 struct dma_tx_state state;
52 dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
54 count = dma->rx_size - state.residue;
56 tty_insert_flip_string(tty_port, dma->rx_buf, count);
57 p->port.icount.rx += count;
59 tty_flip_buffer_push(tty_port);
62 int serial8250_tx_dma(struct uart_8250_port *p)
64 struct uart_8250_dma *dma = p->dma;
65 struct circ_buf *xmit = &p->port.state->xmit;
66 struct dma_async_tx_descriptor *desc;
67 struct uart_port *up = &p->port;
70 if (dma->tx_running) {
72 dmaengine_pause(dma->txchan);
73 uart_xchar_out(up, UART_TX);
74 dmaengine_resume(dma->txchan);
77 } else if (up->x_char) {
78 uart_xchar_out(up, UART_TX);
81 if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) {
82 /* We have been called from __dma_tx_complete() */
86 dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
88 serial8250_do_prepare_tx_dma(p);
90 desc = dmaengine_prep_slave_single(dma->txchan,
91 dma->tx_addr + xmit->tail,
92 dma->tx_size, DMA_MEM_TO_DEV,
93 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
100 desc->callback = __dma_tx_complete;
101 desc->callback_param = p;
103 dma->tx_cookie = dmaengine_submit(desc);
105 dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
106 UART_XMIT_SIZE, DMA_TO_DEVICE);
108 dma_async_issue_pending(dma->txchan);
109 serial8250_clear_THRI(p);
119 int serial8250_rx_dma(struct uart_8250_port *p)
121 struct uart_8250_dma *dma = p->dma;
122 struct dma_async_tx_descriptor *desc;
127 serial8250_do_prepare_rx_dma(p);
129 desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
130 dma->rx_size, DMA_DEV_TO_MEM,
131 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
136 desc->callback = __dma_rx_complete;
137 desc->callback_param = p;
139 dma->rx_cookie = dmaengine_submit(desc);
141 dma_async_issue_pending(dma->rxchan);
146 void serial8250_rx_dma_flush(struct uart_8250_port *p)
148 struct uart_8250_dma *dma = p->dma;
150 if (dma->rx_running) {
151 dmaengine_pause(dma->rxchan);
152 __dma_rx_complete(p);
153 dmaengine_terminate_async(dma->rxchan);
156 EXPORT_SYMBOL_GPL(serial8250_rx_dma_flush);
158 int serial8250_request_dma(struct uart_8250_port *p)
160 struct uart_8250_dma *dma = p->dma;
161 phys_addr_t rx_dma_addr = dma->rx_dma_addr ?
162 dma->rx_dma_addr : p->port.mapbase;
163 phys_addr_t tx_dma_addr = dma->tx_dma_addr ?
164 dma->tx_dma_addr : p->port.mapbase;
166 struct dma_slave_caps caps;
169 /* Default slave configuration parameters */
170 dma->rxconf.direction = DMA_DEV_TO_MEM;
171 dma->rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
172 dma->rxconf.src_addr = rx_dma_addr + UART_RX;
174 dma->txconf.direction = DMA_MEM_TO_DEV;
175 dma->txconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
176 dma->txconf.dst_addr = tx_dma_addr + UART_TX;
179 dma_cap_set(DMA_SLAVE, mask);
181 /* Get a channel for RX */
182 dma->rxchan = dma_request_slave_channel_compat(mask,
183 dma->fn, dma->rx_param,
188 /* 8250 rx dma requires dmaengine driver to support pause/terminate */
189 ret = dma_get_slave_caps(dma->rxchan, &caps);
192 if (!caps.cmd_pause || !caps.cmd_terminate ||
193 caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
198 dmaengine_slave_config(dma->rxchan, &dma->rxconf);
200 /* Get a channel for TX */
201 dma->txchan = dma_request_slave_channel_compat(mask,
202 dma->fn, dma->tx_param,
209 /* 8250 tx dma requires dmaengine driver to support terminate */
210 ret = dma_get_slave_caps(dma->txchan, &caps);
213 if (!caps.cmd_terminate) {
218 dmaengine_slave_config(dma->txchan, &dma->txconf);
222 dma->rx_size = PAGE_SIZE;
224 dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
225 &dma->rx_addr, GFP_KERNEL);
232 dma->tx_addr = dma_map_single(dma->txchan->device->dev,
233 p->port.state->xmit.buf,
236 if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) {
237 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size,
238 dma->rx_buf, dma->rx_addr);
243 dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
247 dma_release_channel(dma->txchan);
249 dma_release_channel(dma->rxchan);
252 EXPORT_SYMBOL_GPL(serial8250_request_dma);
254 void serial8250_release_dma(struct uart_8250_port *p)
256 struct uart_8250_dma *dma = p->dma;
261 /* Release RX resources */
262 dmaengine_terminate_sync(dma->rxchan);
263 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
265 dma_release_channel(dma->rxchan);
268 /* Release TX resources */
269 dmaengine_terminate_sync(dma->txchan);
270 dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
271 UART_XMIT_SIZE, DMA_TO_DEVICE);
272 dma_release_channel(dma->txchan);
276 dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
278 EXPORT_SYMBOL_GPL(serial8250_release_dma);