[PATCH v2 0/2] serial: fsl_lpuart: DMA improvements

[PATCH v2 0/2] serial: fsl_lpuart: DMA improvements

[Stefan Agner]

This are the remaining to patches 2 and 4 from the first version of
this patchset. The patchset is based on the fixes patchset.
https://lkml.org/lkml/2015/1/9/757

Changes since v1:
- Reorderred and rebased on v3.19-rc3

Stefan Agner (2):
  serial: fsl_lpuart: move DMA channel request to probe
  serial: fsl_lpuart: update RX timer on successful DMA transfer

 drivers/tty/serial/fsl_lpuart.c | 97 +++++++++++++++++++----------------------
 1 file changed, 45 insertions(+), 52 deletions(-)

-- 
2.2.1

[PATCH v2 1/2] serial: fsl_lpuart: move DMA channel request to probe

[Stefan Agner]

Move the DMA channel request to probe to avoid requesting the DMA
channel on each opening of the ttyLPx device. This also fixes a
potential issue that TX channel is not freed when only RX channel
allocation fails. The DMA channels are now handled independently,
so one could use UART with DMA only in TX direction for instance.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/tty/serial/fsl_lpuart.c | 96 +++++++++++++++++++----------------------
 1 file changed, 44 insertions(+), 52 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index e95c497..0ea0af7 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -237,7 +237,8 @@ struct lpuart_port {
 	unsigned int		rxfifo_size;
 	bool			lpuart32;
 
-	bool			lpuart_dma_use;
+	bool			lpuart_dma_tx_use;
+	bool			lpuart_dma_rx_use;
 	struct dma_chan		*dma_tx_chan;
 	struct dma_chan		*dma_rx_chan;
 	struct dma_async_tx_descriptor  *dma_tx_desc;
@@ -568,7 +569,7 @@ static void lpuart_start_tx(struct uart_port *port)
 	temp = readb(port->membase + UARTCR2);
 	writeb(temp | UARTCR2_TIE, port->membase + UARTCR2);
 
-	if (sport->lpuart_dma_use) {
+	if (sport->lpuart_dma_tx_use) {
 		if (!uart_circ_empty(xmit) && !sport->dma_tx_in_progress)
 			lpuart_prepare_tx(sport);
 	} else {
@@ -761,13 +762,13 @@ static irqreturn_t lpuart_int(int irq, void *dev_id)
 	crdma = readb(sport->port.membase + UARTCR5);
 
 	if (sts & UARTSR1_RDRF && !(crdma & UARTCR5_RDMAS)) {
-		if (sport->lpuart_dma_use)
+		if (sport->lpuart_dma_rx_use)
 			lpuart_prepare_rx(sport);
 		else
 			lpuart_rxint(irq, dev_id);
 	}
 	if (sts & UARTSR1_TDRE && !(crdma & UARTCR5_TDMAS)) {
-		if (sport->lpuart_dma_use)
+		if (sport->lpuart_dma_tx_use)
 			lpuart_pio_tx(sport);
 		else
 			lpuart_txint(irq, dev_id);
@@ -950,26 +951,17 @@ static int lpuart_dma_tx_request(struct uart_port *port)
 {
 	struct lpuart_port *sport = container_of(port,
 					struct lpuart_port, port);
-	struct dma_chan *tx_chan;
 	struct dma_slave_config dma_tx_sconfig;
 	dma_addr_t dma_bus;
 	unsigned char *dma_buf;
 	int ret;
 
-	tx_chan  = dma_request_slave_channel(sport->port.dev, "tx");
-
-	if (!tx_chan) {
-		dev_err(sport->port.dev, "Dma tx channel request failed!\n");
-		return -ENODEV;
-	}
-
-	dma_bus = dma_map_single(tx_chan->device->dev,
+	dma_bus = dma_map_single(sport->dma_tx_chan->device->dev,
 				sport->port.state->xmit.buf,
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
 
-	if (dma_mapping_error(tx_chan->device->dev, dma_bus)) {
+	if (dma_mapping_error(sport->dma_tx_chan->device->dev, dma_bus)) {
 		dev_err(sport->port.dev, "dma_map_single tx failed\n");
-		dma_release_channel(tx_chan);
 		return -ENOMEM;
 	}
 
@@ -978,16 +970,14 @@ static int lpuart_dma_tx_request(struct uart_port *port)
 	dma_tx_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
 	dma_tx_sconfig.dst_maxburst = sport->txfifo_size;
 	dma_tx_sconfig.direction = DMA_MEM_TO_DEV;
-	ret = dmaengine_slave_config(tx_chan, &dma_tx_sconfig);
+	ret = dmaengine_slave_config(sport->dma_tx_chan, &dma_tx_sconfig);
 
 	if (ret < 0) {
 		dev_err(sport->port.dev,
 				"Dma slave config failed, err = %d\n", ret);
-		dma_release_channel(tx_chan);
 		return ret;
 	}
 
-	sport->dma_tx_chan = tx_chan;
 	sport->dma_tx_buf_virt = dma_buf;
 	sport->dma_tx_buf_bus = dma_bus;
 	sport->dma_tx_in_progress = 0;
@@ -999,34 +989,24 @@ static int lpuart_dma_rx_request(struct uart_port *port)
 {
 	struct lpuart_port *sport = container_of(port,
 					struct lpuart_port, port);
-	struct dma_chan *rx_chan;
 	struct dma_slave_config dma_rx_sconfig;
 	dma_addr_t dma_bus;
 	unsigned char *dma_buf;
 	int ret;
 
-	rx_chan  = dma_request_slave_channel(sport->port.dev, "rx");
-
-	if (!rx_chan) {
-		dev_err(sport->port.dev, "Dma rx channel request failed!\n");
-		return -ENODEV;
-	}
-
 	dma_buf = devm_kzalloc(sport->port.dev,
 				FSL_UART_RX_DMA_BUFFER_SIZE, GFP_KERNEL);
 
 	if (!dma_buf) {
 		dev_err(sport->port.dev, "Dma rx alloc failed\n");
-		dma_release_channel(rx_chan);
 		return -ENOMEM;
 	}
 
-	dma_bus = dma_map_single(rx_chan->device->dev, dma_buf,
+	dma_bus = dma_map_single(sport->dma_rx_chan->device->dev, dma_buf,
 				FSL_UART_RX_DMA_BUFFER_SIZE, DMA_FROM_DEVICE);
 
-	if (dma_mapping_error(rx_chan->device->dev, dma_bus)) {
+	if (dma_mapping_error(sport->dma_rx_chan->device->dev, dma_bus)) {
 		dev_err(sport->port.dev, "dma_map_single rx failed\n");
-		dma_release_channel(rx_chan);
 		return -ENOMEM;
 	}
 
@@ -1034,16 +1014,14 @@ static int lpuart_dma_rx_request(struct uart_port *port)
 	dma_rx_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
 	dma_rx_sconfig.src_maxburst = 1;
 	dma_rx_sconfig.direction = DMA_DEV_TO_MEM;
-	ret = dmaengine_slave_config(rx_chan, &dma_rx_sconfig);
+	ret = dmaengine_slave_config(sport->dma_rx_chan, &dma_rx_sconfig);
 
 	if (ret < 0) {
 		dev_err(sport->port.dev,
 				"Dma slave config failed, err = %d\n", ret);
-		dma_release_channel(rx_chan);
 		return ret;
 	}
 
-	sport->dma_rx_chan = rx_chan;
 	sport->dma_rx_buf_virt = dma_buf;
 	sport->dma_rx_buf_bus = dma_bus;
 	sport->dma_rx_in_progress = 0;
@@ -1055,31 +1033,24 @@ static void lpuart_dma_tx_free(struct uart_port *port)
 {
 	struct lpuart_port *sport = container_of(port,
 					struct lpuart_port, port);
-	struct dma_chan *dma_chan;
 
 	dma_unmap_single(sport->port.dev, sport->dma_tx_buf_bus,
 			UART_XMIT_SIZE, DMA_TO_DEVICE);
-	dma_chan = sport->dma_tx_chan;
-	sport->dma_tx_chan = NULL;
+
 	sport->dma_tx_buf_bus = 0;
 	sport->dma_tx_buf_virt = NULL;
-	dma_release_channel(dma_chan);
 }
 
 static void lpuart_dma_rx_free(struct uart_port *port)
 {
 	struct lpuart_port *sport = container_of(port,
 					struct lpuart_port, port);
-	struct dma_chan *dma_chan;
 
 	dma_unmap_single(sport->port.dev, sport->dma_rx_buf_bus,
 			FSL_UART_RX_DMA_BUFFER_SIZE, DMA_FROM_DEVICE);
 
-	dma_chan = sport->dma_rx_chan;
-	sport->dma_rx_chan = NULL;
 	sport->dma_rx_buf_bus = 0;
 	sport->dma_rx_buf_virt = NULL;
-	dma_release_channel(dma_chan);
 }
 
 static int lpuart_startup(struct uart_port *port)
@@ -1098,17 +1069,21 @@ static int lpuart_startup(struct uart_port *port)
 	sport->rxfifo_size = 0x1 << (((temp >> UARTPFIFO_RXSIZE_OFF) &
 		UARTPFIFO_FIFOSIZE_MASK) + 1);
 
-	/* Whether use dma support by dma request results */
-	if (lpuart_dma_tx_request(port) || lpuart_dma_rx_request(port)) {
-		sport->lpuart_dma_use = false;
-	} else {
-		sport->lpuart_dma_use = true;
+	if (sport->dma_rx_chan && !lpuart_dma_rx_request(port)) {
+		sport->lpuart_dma_rx_use = true;
 		setup_timer(&sport->lpuart_timer, lpuart_timer_func,
 			    (unsigned long)sport);
+	} else
+		sport->lpuart_dma_rx_use = false;
+
+
+	if (sport->dma_tx_chan && !lpuart_dma_tx_request(port)) {
+		sport->lpuart_dma_tx_use = true;
 		temp = readb(port->membase + UARTCR5);
 		temp &= ~UARTCR5_RDMAS;
 		writeb(temp | UARTCR5_TDMAS, port->membase + UARTCR5);
-	}
+	} else
+		sport->lpuart_dma_tx_use = false;
 
 	ret = devm_request_irq(port->dev, port->irq, lpuart_int, 0,
 				DRIVER_NAME, sport);
@@ -1179,12 +1154,13 @@ static void lpuart_shutdown(struct uart_port *port)
 
 	devm_free_irq(port->dev, port->irq, sport);
 
-	if (sport->lpuart_dma_use) {
+	if (sport->lpuart_dma_rx_use) {
+		lpuart_dma_rx_free(&sport->port);
 		del_timer_sync(&sport->lpuart_timer);
-
-		lpuart_dma_tx_free(port);
-		lpuart_dma_rx_free(port);
 	}
+
+	if (sport->lpuart_dma_tx_use)
+		lpuart_dma_tx_free(&sport->port);
 }
 
 static void lpuart32_shutdown(struct uart_port *port)
@@ -1306,7 +1282,7 @@ lpuart_set_termios(struct uart_port *port, struct ktermios *termios,
 	/* update the per-port timeout */
 	uart_update_timeout(port, termios->c_cflag, baud);
 
-	if (sport->lpuart_dma_use) {
+	if (sport->lpuart_dma_rx_use) {
 		/* Calculate delay for 1.5 DMA buffers */
 		sport->dma_rx_timeout = (sport->port.timeout - HZ / 50) *
 					FSL_UART_RX_DMA_BUFFER_SIZE * 3 /
@@ -1835,6 +1811,16 @@ static int lpuart_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	sport->dma_tx_chan = dma_request_slave_channel(sport->port.dev, "tx");
+	if (!sport->dma_tx_chan)
+		dev_info(sport->port.dev, "DMA tx channel request failed, "
+				"operating without tx DMA\n");
+
+	sport->dma_rx_chan = dma_request_slave_channel(sport->port.dev, "rx");
+	if (!sport->dma_rx_chan)
+		dev_info(sport->port.dev, "DMA rx channel request failed, "
+				"operating without rx DMA\n");
+
 	return 0;
 }
 
@@ -1846,6 +1832,12 @@ static int lpuart_remove(struct platform_device *pdev)
 
 	clk_disable_unprepare(sport->clk);
 
+	if (sport->dma_tx_chan)
+		dma_release_channel(sport->dma_tx_chan);
+
+	if (sport->dma_rx_chan)
+		dma_release_channel(sport->dma_rx_chan);
+
 	return 0;
 }
 
-- 
2.2.1

[PATCH v2 2/2] serial: fsl_lpuart: update RX timer on successful DMA transfer

[Stefan Agner]

To end a DMA transfer which did not consume a whole buffer (e.g. one
character only), a RX timer is used. When lots of data are received
the DMA transfer will complete and setup another DMA transfer, which
in turn might complete again. In this cases, it is not necessary to
abort the DMA transfers using the RX timer. This change pushes the
RX timer timeout into the future each time a DMA transfer completed.

Aborting the DMA was not very harmful, since the next received
character lead to setup of another RX DMA.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/tty/serial/fsl_lpuart.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 0ea0af7..914f9a2 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -462,6 +462,7 @@ static void lpuart_dma_rx_complete(void *arg)
 	unsigned long flags;
 
 	async_tx_ack(sport->dma_rx_desc);
+	mod_timer(&sport->lpuart_timer, jiffies + sport->dma_rx_timeout);
 
 	spin_lock_irqsave(&sport->port.lock, flags);
 
-- 
2.2.1