Commit 8ee161ce authored Mar 15, 2012 by Ville Syrjala Committed by Jean Delvare Mar 15, 2012

i2c-algo-bit: Fix spurious SCL timeouts under heavy load



When the system is under heavy load, there can be a significant delay
between the getscl() and time_after() calls inside sclhi(). That delay
may cause the time_after() check to trigger after SCL has gone high,
causing sclhi() to return -ETIMEDOUT.

To fix the problem, double check that SCL is still low after the
timeout has been reached, before deciding to return -ETIMEDOUT.

Signed-off-by: Ville Syrjala <syrjala@sci.fi>
Cc: stable@vger.kernel.org
Signed-off-by: Jean Delvare <khali@linux-fr.org>

parent 834aa6f3

drivers/i2c/algos/i2c-algo-bit.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -103,8 +103,14 @@ static int sclhi(struct i2c_algo_bit_data *adap)
		* chips may hold it low ("clock stretching") while they
		* are processing data internally.
		*/
		if (time_after(jiffies, start + adap->timeout))
		if (time_after(jiffies, start + adap->timeout)) {
		/* Test one last time, as we may have been preempted
		* between last check and timeout test.
		*/
		if (getscl(adap))
		break;
		return -ETIMEDOUT;
		}
		cond_resched();
		}
		#ifdef DEBUG