Commit c68c62 ("i2c: mvtwsi: Make delay times frequency-dependent") extensively used the ndelay function with a calculated parameter which is dependant on the configured frequency of the I2C bus. If standard speed is employed, the parameter is usually 10000 (10000ns period length for 100kHz frequency).

But, since the arm architecture does not implement a proper version of ndelay, the fallback default from include/linux/compat.h is used, which defines every ndelay as udelay(1). This causes problems for slower speeds on arm, since the delay time is now 9us too short for the desired frequency, which leads to random failures of the I2C interface.

To remedy this, we implement a proper, parameter-aware ndelay fallback for architectures that don't implement a real ndelay function.

Reported-By: Jason Brown Jason.brown@apcon.com To: Tom Rini trini@konsulko.com To: Heiko Schocher hs@denx.de Signed-off-by: Mario Six mario.six@gdsys.cc --- include/linux/compat.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/compat.h b/include/linux/compat.h index c7fd649..533983f 100644 --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -15,7 +15,7 @@ struct p_current{

extern struct p_current *current;

-#define ndelay(x) udelay(1) +#define ndelay(x) udelay((x) < 1000 ? 1 : (x)/1000)

#define dev_dbg(dev, fmt, args...) \ debug(fmt, ##args) -- 2.9.0