1 files changed, 295 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
new file mode 100644
index 000000000..33ce4b218
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -0,0 +1,295 @@
+// 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;
+
+	xmit->tail += dma->tx_size;
+	xmit->tail &= UART_XMIT_SIZE - 1;
+	p->port.icount.tx += dma->tx_size;
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&p->port);
+
+	ret = serial8250_tx_dma(p);
+	if (ret)
+		serial8250_set_THRI(p);
+
+	spin_unlock_irqrestore(&p->port.lock, flags);
+}
+
+static void __dma_rx_complete(void *param)
+{
+	struct uart_8250_port	*p = param;
+	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);
+	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() */
+		serial8250_rpm_put_tx(p);
+		return 0;
+	}
+
+	dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+
+	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);
+	if (dma->tx_err) {
+		dma->tx_err = 0;
+		serial8250_clear_THRI(p);
+	}
+	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;
+
+	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);