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

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Date:	Thu,  9 Jun 2016 15:16:33 +0300
From:	Nandor Han <nandor.han@...com>
To:	=Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>
Cc:	Nandor Han <nandor.han@...com>, dmaengine@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH RFC 4/4] serial: imx-serial - update RX error counters when DMA is used

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.han@...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