drivers/tty/serial/8250/8250_dma.c - linux - Git at Google

 // 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);

 	uart_port_lock_irqsave(&p->port, &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);

 	uart_port_unlock_irqrestore(&p->port, 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;

 	uart_port_lock_irqsave(&p->port, &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);
 	uart_port_unlock_irqrestore(&p->port, 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);
	// 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);

	uart_port_lock_irqsave(&p->port, &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);

	uart_port_unlock_irqrestore(&p->port, 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;

	uart_port_lock_irqsave(&p->port, &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);
	uart_port_unlock_irqrestore(&p->port, 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);