| From 8ee161ce5e0cfc689eb677f227a6248191165fac Mon Sep 17 00:00:00 2001 |
| From: Ville Syrjala <syrjala@sci.fi> |
| Date: Thu, 15 Mar 2012 18:11:05 +0100 |
| Subject: i2c-algo-bit: Fix spurious SCL timeouts under heavy load |
| |
| From: Ville Syrjala <syrjala@sci.fi> |
| |
| 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 <syrjala@sci.fi> |
| Signed-off-by: Jean Delvare <khali@linux-fr.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/i2c/algos/i2c-algo-bit.c | 8 +++++++- |
| 1 file changed, 7 insertions(+), 1 deletion(-) |
| |
| --- 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_dat |
| * 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 |
