[PATCH RFC 4/4] serial: imx-serial - update RX error counters when DMA is used

[Nandor Han]

Update error couters when DMA is used for receiving data. Do
this by using DMA transaction error event instead error interrupts
to reduce interrupt load.

Signed-off-by: Nandor Han <nandor....@ge.com>
---
 drivers/tty/serial/imx.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 1912136..08ccfe1 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -704,6 +704,7 @@ out:
        return IRQ_HANDLED;
 }
 
+static void clear_rx_errors(struct imx_port *sport);
 static int start_rx_dma(struct imx_port *sport);
 /*
  * If the RXFIFO is filled with some data, and then we
@@ -729,6 +730,11 @@ static void imx_dma_rxint(struct imx_port *sport)
                temp &= ~(UCR2_ATEN);
                writel(temp, sport->port.membase + UCR2);
 
+               /* disable the rx errors interrupts */
+               temp = readl(sport->port.membase + UCR4);
+               temp &= ~UCR4_OREN;
+               writel(temp, sport->port.membase + UCR4);
+
                /* tell the DMA to receive the data. */
                start_rx_dma(sport);
        }
@@ -961,6 +967,7 @@ static void dma_rx_callback(void *data)
 
        if (status == DMA_ERROR) {
                dev_err(sport->port.dev, "DMA transaction error.\n");
+               clear_rx_errors(sport);
                return;
        }
 
@@ -1057,6 +1064,31 @@ static int start_rx_dma(struct imx_port *sport)
        return 0;
 }
 
+static void clear_rx_errors(struct imx_port *sport)
+{
+       unsigned int status_usr1, status_usr2;
+
+       status_usr1 = readl(sport->port.membase + USR1);
+       status_usr2 = readl(sport->port.membase + USR2);
+
+       if (status_usr2 & USR2_BRCD) {
+               sport->port.icount.brk++;
+               writel(USR2_BRCD, sport->port.membase + USR2);
+       } else if (status_usr1 & USR1_FRAMERR) {
+               sport->port.icount.frame++;
+               writel(USR1_FRAMERR, sport->port.membase + USR1);
+       } else if (status_usr1 & USR1_PARITYERR) {
+               sport->port.icount.parity++;
+               writel(USR1_PARITYERR, sport->port.membase + USR1);
+       }
+
+       if (status_usr2 & USR2_ORE) {
+               sport->port.icount.overrun++;
+               writel(USR2_ORE, sport->port.membase + USR2);
+       }
+
+}
+
 #define TXTL_DEFAULT 2 /* reset default */
 #define RXTL_DEFAULT 1 /* reset default */
 #define TXTL_DMA 8 /* DMA burst setting */
-- 
2.8.3