linux-kernel - [RFC PATCH 4/7] serial: 8250_dma: enqueue RX dma again on completion.

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Message-Id: <1406660344-25307-5-git-send-email-bigeasy@linutronix.de>
Date:	Tue, 29 Jul 2014 20:59:01 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	linux-serial@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, tony@...mide.com,
	balbi@...com, Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: [RFC PATCH 4/7] serial: 8250_dma: enqueue RX dma again on completion.

The omap needs a DMA request pending right away. If it is enqueued once
the bytes are in the FIFO then nothing will happen and the FIFO will be
later purged via RX-timeout interrupt.
This patch requeues RX-DMA request on completion but not if it was
canceled due to the RX-timeout.

Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 drivers/tty/serial/8250/8250_core.c |  3 +++
 drivers/tty/serial/8250/8250_dma.c  | 12 +++++++++---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 7a33c30..098ff02 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1556,6 +1556,9 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 
 		if (!up->dma || dma_err)
 			status = serial8250_rx_chars(up, status);
+
+		if (dma_err == -ETIMEDOUT && port->type == PORT_OMAP_16750)
+			serial8250_rx_dma(up, 0);
 	}
 	serial8250_modem_status(up);
 	if (!up->dma && (status & UART_LSR_THRE))
diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index f9ef69f..acb0a87 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -49,9 +49,8 @@ static void __dma_tx_complete(void *param)
 	spin_unlock_irqrestore(&p->port.lock, flags);
 }
 
-static void __dma_rx_complete(void *param)
+static void __dma_rx_do_complete(struct uart_8250_port *p, bool timeout)
 {
-	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;
@@ -67,10 +66,17 @@ static void __dma_rx_complete(void *param)
 
 	tty_insert_flip_string(tty_port, dma->rx_buf, count);
 	p->port.icount.rx += count;
+	if (!timeout && p->port.type == PORT_OMAP_16750)
+		serial8250_rx_dma(p, 0);
 
 	tty_flip_buffer_push(tty_port);
 }
 
+static void __dma_rx_complete(void *param)
+{
+	__dma_rx_do_complete(param, false);
+}
+
 int serial8250_tx_dma(struct uart_8250_port *p)
 {
 	struct uart_8250_dma		*dma = p->dma;
@@ -126,7 +132,7 @@ int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
 		 */
 		if (dma_status == DMA_IN_PROGRESS) {
 			dmaengine_pause(dma->rxchan);
-			__dma_rx_complete(p);
+			__dma_rx_do_complete(p, true);
 		}
 		return -ETIMEDOUT;
 	default:
-- 
2.0.1

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