serial: imx-serial - update RX error counters when DMA is used

Update error counters when DMA is used for receiving data. Do
this by using DMA transaction error event instead error interrupts
to reduce interrupt load.
Tested-by: Peter Senna Tschudin <peter.senna@collabora.com>
Acked-by: Peter Senna Tschudin <peter.senna@collabora.com>
Signed-off-by: Nandor Han <nandor.han@ge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -704,6 +704,7 @@ static irqreturn_t imx_rxint(int irq, void *dev_id)
 	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 */