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);
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;
72 if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) {
73 /* We have been called from __dma_tx_complete() */
74 serial8250_rpm_put_tx(p);
78 dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
80 desc = dmaengine_prep_slave_single(dma->txchan,
81 dma->tx_addr + xmit->tail,
82 dma->tx_size, DMA_MEM_TO_DEV,
83 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
90 desc->callback = __dma_tx_complete;
91 desc->callback_param = p;
93 dma->tx_cookie = dmaengine_submit(desc);
95 dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
96 UART_XMIT_SIZE, DMA_TO_DEVICE);
98 dma_async_issue_pending(dma->txchan);
101 serial8250_clear_THRI(p);
109 int serial8250_rx_dma(struct uart_8250_port *p)
111 struct uart_8250_dma *dma = p->dma;
112 struct dma_async_tx_descriptor *desc;
117 desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
118 dma->rx_size, DMA_DEV_TO_MEM,
119 DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
124 desc->callback = __dma_rx_complete;
125 desc->callback_param = p;
127 dma->rx_cookie = dmaengine_submit(desc);
129 dma_async_issue_pending(dma->rxchan);
134 void serial8250_rx_dma_flush(struct uart_8250_port *p)
136 struct uart_8250_dma *dma = p->dma;
138 if (dma->rx_running) {
139 dmaengine_pause(dma->rxchan);
140 __dma_rx_complete(p);
141 dmaengine_terminate_async(dma->rxchan);
144 EXPORT_SYMBOL_GPL(serial8250_rx_dma_flush);
146 int serial8250_request_dma(struct uart_8250_port *p)
148 struct uart_8250_dma *dma = p->dma;
149 phys_addr_t rx_dma_addr = dma->rx_dma_addr ?
150 dma->rx_dma_addr : p->port.mapbase;
151 phys_addr_t tx_dma_addr = dma->tx_dma_addr ?
152 dma->tx_dma_addr : p->port.mapbase;
154 struct dma_slave_caps caps;
157 /* Default slave configuration parameters */
158 dma->rxconf.direction = DMA_DEV_TO_MEM;
159 dma->rxconf.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
160 dma->rxconf.src_addr = rx_dma_addr + UART_RX;
162 dma->txconf.direction = DMA_MEM_TO_DEV;
163 dma->txconf.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
164 dma->txconf.dst_addr = tx_dma_addr + UART_TX;
167 dma_cap_set(DMA_SLAVE, mask);
169 /* Get a channel for RX */
170 dma->rxchan = dma_request_slave_channel_compat(mask,
171 dma->fn, dma->rx_param,
176 /* 8250 rx dma requires dmaengine driver to support pause/terminate */
177 ret = dma_get_slave_caps(dma->rxchan, &caps);
180 if (!caps.cmd_pause || !caps.cmd_terminate ||
181 caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
186 dmaengine_slave_config(dma->rxchan, &dma->rxconf);
188 /* Get a channel for TX */
189 dma->txchan = dma_request_slave_channel_compat(mask,
190 dma->fn, dma->tx_param,
197 /* 8250 tx dma requires dmaengine driver to support terminate */
198 ret = dma_get_slave_caps(dma->txchan, &caps);
201 if (!caps.cmd_terminate) {
206 dmaengine_slave_config(dma->txchan, &dma->txconf);
210 dma->rx_size = PAGE_SIZE;
212 dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
213 &dma->rx_addr, GFP_KERNEL);
220 dma->tx_addr = dma_map_single(dma->txchan->device->dev,
221 p->port.state->xmit.buf,
224 if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) {
225 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size,
226 dma->rx_buf, dma->rx_addr);
231 dev_dbg_ratelimited(p->port.dev, "got both dma channels\n");
235 dma_release_channel(dma->txchan);
237 dma_release_channel(dma->rxchan);
240 EXPORT_SYMBOL_GPL(serial8250_request_dma);
242 void serial8250_release_dma(struct uart_8250_port *p)
244 struct uart_8250_dma *dma = p->dma;
249 /* Release RX resources */
250 dmaengine_terminate_sync(dma->rxchan);
251 dma_free_coherent(dma->rxchan->device->dev, dma->rx_size, dma->rx_buf,
253 dma_release_channel(dma->rxchan);
256 /* Release TX resources */
257 dmaengine_terminate_sync(dma->txchan);
258 dma_unmap_single(dma->txchan->device->dev, dma->tx_addr,
259 UART_XMIT_SIZE, DMA_TO_DEVICE);
260 dma_release_channel(dma->txchan);
264 dev_dbg_ratelimited(p->port.dev, "dma channels released\n");
266 EXPORT_SYMBOL_GPL(serial8250_release_dma);