[PATCH 08/16] tty: serial: 8250_dma: enqueue RX dma again on completion.

[Sebastian Andrzej Siewior]

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 enqueues RX-DMA request on completion but not if it was
aborted on error. The first enqueue will happen in the driver in
startup.

Reviewed-by: Tony Lindgren <tony at atomide.com>
Tested-by: Tony Lindgren <tony at atomide.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
---
 drivers/tty/serial/8250/8250.h      |  3 ++-
 drivers/tty/serial/8250/8250_core.c |  3 +++
 drivers/tty/serial/8250/8250_dma.c  | 12 +++++++++---
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index a63d198f8d03..fbed1636e9c4 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -80,7 +80,8 @@ struct serial8250_config {
 #define UART_BUG_NOMSR	(1 << 2)	/* UART has buggy MSR status bits (Au1x00) */
 #define UART_BUG_THRE	(1 << 3)	/* UART has buggy THRE reassertion */
 #define UART_BUG_PARITY	(1 << 4)	/* UART mishandles parity if FIFO enabled */
-
+#define UART_BUG_DMA_RX	(1 << 5)	/* UART needs DMA RX req before there is
+					   data in FIFO */
 #define PROBE_RSA	(1 << 0)
 #define PROBE_ANY	(~0)
 
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 9f961ea82564..39b1c7318f17 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1592,6 +1592,9 @@ 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 && up->bugs & UART_BUG_DMA_RX)
+			serial8250_rx_dma(up, 0);
 	}
 	serial8250_modem_status(up);
 	if ((!up->dma || (up->dma && up->dma->tx_err)) &&
diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 69e54abb6e71..3674900a1f14 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -50,9 +50,8 @@ 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 error)
 {
-	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;
@@ -68,10 +67,17 @@ static void __dma_rx_complete(void *param)
 
 	tty_insert_flip_string(tty_port, dma->rx_buf, count);
 	p->port.icount.rx += count;
+	if (!error && p->bugs & UART_BUG_DMA_RX)
+		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;
@@ -139,7 +145,7 @@ 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:
-- 
2.1.0