From: Ville Syrjala Date: Thu, 15 Mar 2012 17:11:05 +0000 (+0100) Subject: i2c-algo-bit: Fix spurious SCL timeouts under heavy load X-Git-Tag: v3.0.25~1 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=35f68010b4311eacf6340473b062418715d68a39;p=karo-tx-linux.git i2c-algo-bit: Fix spurious SCL timeouts under heavy load commit 8ee161ce5e0cfc689eb677f227a6248191165fac upstream. 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 Signed-off-by: Jean Delvare Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c index eca3bcc4599d..f2ce8c36816f 100644 --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -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