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

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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>
This commit is contained in:
Ville Syrjala 2012-03-15 18:11:05 +01:00 committed by Jean Delvare
parent 834aa6f30c
commit 8ee161ce5e
1 changed files with 7 additions and 1 deletions
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8
drivers/i2c/algos/i2c-algo-bit.c
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@ -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