[EXT] Re: iMX6/UART imprecise external abort

Uwe Kleine-König u.kleine-koenig at pengutronix.de
Wed Jan 8 03:23:15 PST 2020


Hello,

On Tue, Jan 07, 2020 at 11:24:06PM +0100, Uwe Kleine-König wrote:
> I will look into this again tomorrow when I'm well rested and create a
> patch.

Here you go, for now without proper commit log etc.pp.

Please test if this fixes your problems.

I currently don't have the setup to trigger this bug, but normal console
usage still works for me.

Best regards
Uwe

-------->8--------
>From 025a72c6de6df8b71414378a0297568df371bd73 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig at pengutronix.de>
Date: Wed, 8 Jan 2020 09:47:20 +0100
Subject: [PATCH RFT] serial: imx: fix a race condition in receive path

---
 drivers/tty/serial/imx.c | 52 ++++++++++++++++++++++++++++++----------
 1 file changed, 39 insertions(+), 13 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index a9e20e6c63ad..679b2de27c4d 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -700,22 +700,33 @@ static void imx_uart_start_tx(struct uart_port *port)
 	}
 }
 
-static irqreturn_t imx_uart_rtsint(int irq, void *dev_id)
+static irqreturn_t __imx_uart_rtsint(int irq, void *dev_id)
 {
 	struct imx_port *sport = dev_id;
 	u32 usr1;
 
-	spin_lock(&sport->port.lock);
-
 	imx_uart_writel(sport, USR1_RTSD, USR1);
 	usr1 = imx_uart_readl(sport, USR1) & USR1_RTSS;
 	uart_handle_cts_change(&sport->port, !!usr1);
 	wake_up_interruptible(&sport->port.state->port.delta_msr_wait);
 
-	spin_unlock(&sport->port.lock);
 	return IRQ_HANDLED;
 }
 
+static irqreturn_t imx_uart_rtsint(int irq, void *dev_id)
+{
+	struct imx_port *sport = dev_id;
+	irqreturn_t ret;
+
+	spin_lock(&sport->port.lock);
+
+	ret = __imx_uart_rtsint(irq, dev_id);
+
+	spin_unlock(&sport->port.lock);
+
+	return ret;
+}
+
 static irqreturn_t imx_uart_txint(int irq, void *dev_id)
 {
 	struct imx_port *sport = dev_id;
@@ -726,14 +737,12 @@ static irqreturn_t imx_uart_txint(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static irqreturn_t imx_uart_rxint(int irq, void *dev_id)
+static irqreturn_t __imx_uart_rxint(int irq, void *dev_id)
 {
 	struct imx_port *sport = dev_id;
 	unsigned int rx, flg, ignored = 0;
 	struct tty_port *port = &sport->port.state->port;
 
-	spin_lock(&sport->port.lock);
-
 	while (imx_uart_readl(sport, USR2) & USR2_RDR) {
 		u32 usr2;
 
@@ -792,11 +801,26 @@ static irqreturn_t imx_uart_rxint(int irq, void *dev_id)
 	}
 
 out:
-	spin_unlock(&sport->port.lock);
 	tty_flip_buffer_push(port);
+
 	return IRQ_HANDLED;
 }
 
+static irqreturn_t imx_uart_rxint(int irq, void *dev_id)
+{
+	struct imx_port *sport = dev_id;
+	struct tty_port *port = &sport->port.state->port;
+	irqreturn_t ret;
+
+	spin_lock(&sport->port.lock);
+
+	ret = __imx_uart_rxint(irq, dev_id);
+
+	spin_unlock(&sport->port.lock);
+
+	return ret;
+}
+
 static void imx_uart_clear_rx_errors(struct imx_port *sport);
 
 /*
@@ -855,6 +879,8 @@ static irqreturn_t imx_uart_int(int irq, void *dev_id)
 	unsigned int usr1, usr2, ucr1, ucr2, ucr3, ucr4;
 	irqreturn_t ret = IRQ_NONE;
 
+	spin_lock(&sport->port.lock);
+
 	usr1 = imx_uart_readl(sport, USR1);
 	usr2 = imx_uart_readl(sport, USR2);
 	ucr1 = imx_uart_readl(sport, UCR1);
@@ -888,27 +914,25 @@ static irqreturn_t imx_uart_int(int irq, void *dev_id)
 		usr2 &= ~USR2_ORE;
 
 	if (usr1 & (USR1_RRDY | USR1_AGTIM)) {
-		imx_uart_rxint(irq, dev_id);
+		__imx_uart_rxint(irq, dev_id);
 		ret = IRQ_HANDLED;
 	}
 
 	if ((usr1 & USR1_TRDY) || (usr2 & USR2_TXDC)) {
-		imx_uart_txint(irq, dev_id);
+		imx_uart_transmit_buffer(sport);
 		ret = IRQ_HANDLED;
 	}
 
 	if (usr1 & USR1_DTRD) {
 		imx_uart_writel(sport, USR1_DTRD, USR1);
 
-		spin_lock(&sport->port.lock);
 		imx_uart_mctrl_check(sport);
-		spin_unlock(&sport->port.lock);
 
 		ret = IRQ_HANDLED;
 	}
 
 	if (usr1 & USR1_RTSD) {
-		imx_uart_rtsint(irq, dev_id);
+		__imx_uart_rtsint(irq, dev_id);
 		ret = IRQ_HANDLED;
 	}
 
@@ -923,6 +947,8 @@ static irqreturn_t imx_uart_int(int irq, void *dev_id)
 		ret = IRQ_HANDLED;
 	}
 
+	spin_unlock(&sport->port.lock);
+
 	return ret;
 }
 
-- 
2.24.0



-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |



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