[PATCH v1 06/12] serial: 8250_dma: stop ongoing RX DMA on exception

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

If we get an exeption interrupt. i.e. UART_IIR_RLSI, stop any ongoing RX DMA
transfer otherwise it might generates more spurious interrupts and make port
unavailable anymore.

As has been seen on Intel Broxton system:
...
[  168.526281] serial8250: too much work for irq5
[  168.535908] serial8250: too much work for irq5
[  173.449464] serial8250_interrupt: 4439 callbacks suppressed
[  173.455694] serial8250: too much work for irq5
...

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/tty/serial/8250/8250_dma.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 9d80bb1..b134bec 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -110,6 +110,16 @@ err:
 	return ret;
 }
 
+static void __dma_rx_stop(struct uart_8250_port *p, struct uart_8250_dma *dma)
+{
+	if (!dma->rx_running)
+		return;
+
+	dmaengine_pause(dma->rxchan);
+	__dma_rx_complete(p);
+	dmaengine_terminate_async(dma->rxchan);
+}
+
 int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
 {
 	struct uart_8250_dma		*dma = p->dma;
@@ -118,17 +128,14 @@ int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
 	switch (iir & 0x3f) {
 	case UART_IIR_RLSI:
 		/* 8250_core handles errors and break interrupts */
+		__dma_rx_stop(p, dma);
 		return -EIO;
 	case UART_IIR_RX_TIMEOUT:
 		/*
 		 * If RCVR FIFO trigger level was not reached, complete the
 		 * transfer and let 8250_core copy the remaining data.
 		 */
-		if (dma->rx_running) {
-			dmaengine_pause(dma->rxchan);
-			__dma_rx_complete(p);
-			dmaengine_terminate_async(dma->rxchan);
-		}
+		__dma_rx_stop(p, dma);
 		return -ETIMEDOUT;
 	default:
 		break;
-- 
2.8.0.rc3