linux-kernel - [PATCH 3/8] i2c: i2c-bfin-twi: Break dead waiting loop if i2c device misbehaves.

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Date:	Wed, 16 May 2012 15:20:21 +0800
From:	<sonic.zhang@...log.com>
To:	Ben Dooks <ben-linux@...ff.org>,
	Wolfram Sang <w.sang@...gutronix.de>
CC:	<linux-i2c@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
	<uclinux-dist-devel@...ckfin.uclinux.org>,
	Sonic Zhang <sonic.zhang@...log.com>
Subject: [PATCH 3/8] i2c: i2c-bfin-twi: Break dead waiting loop if i2c device misbehaves.

From: Sonic Zhang <sonic.zhang@...log.com>

Some fault i2c device may hold the sda/scl line and cause i2c driver
wait in the BUS busy loop. This patch breaks this potential dead
loop.

Signed-off-by: Sonic Zhang <sonic.zhang@...log.com>

git-svn-id: svn://localhost/svn/linux-kernel/trunk@...1 526b6c2d-f592-4532-a319-5dd88ccb003d
---
 drivers/i2c/busses/i2c-bfin-twi.c |   14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
index 376e331..4abaf59 100644
--- a/drivers/i2c/busses/i2c-bfin-twi.c
+++ b/drivers/i2c/busses/i2c-bfin-twi.c
@@ -294,6 +294,8 @@ static irqreturn_t bfin_twi_interrupt_entry(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+#define BFIN_TWI_BUSY_TIMEOUT	1000
+
 /*
  * One i2c master transfer
  */
@@ -303,12 +305,16 @@ static int bfin_twi_do_master_xfer(struct i2c_adapter *adap,
 	struct bfin_twi_iface *iface = adap->algo_data;
 	struct i2c_msg *pmsg;
 	int rc = 0;
+	unsigned int busy_timeout = BFIN_TWI_BUSY_TIMEOUT;
 
 	if (!(read_CONTROL(iface) & TWI_ENA))
 		return -ENXIO;
 
-	while (read_MASTER_STAT(iface) & BUSBUSY)
+	while (read_MASTER_STAT(iface) & BUSBUSY) {
+		if (--busy_timeout == 0)
+			return -EBUSY;
 		yield();
+	}
 
 	iface->pmsg = msgs;
 	iface->msg_num = num;
@@ -403,12 +409,16 @@ int bfin_twi_do_smbus_xfer(struct i2c_adapter *adap, u16 addr,
 {
 	struct bfin_twi_iface *iface = adap->algo_data;
 	int rc = 0;
+	unsigned int busy_timeout = BFIN_TWI_BUSY_TIMEOUT;
 
 	if (!(read_CONTROL(iface) & TWI_ENA))
 		return -ENXIO;
 
-	while (read_MASTER_STAT(iface) & BUSBUSY)
+	while (read_MASTER_STAT(iface) & BUSBUSY) {
+		if (--busy_timeout == 0)
+			return -EBUSY;
 		yield();
+	}
 
 	iface->writeNum = 0;
 	iface->readNum = 0;
-- 
1.7.0.4


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