[PATCH] at91sam9g45: fix i2c bus speed
Peter Korsgaard
jacmet at sunsite.dk
Wed Sep 22 07:08:29 EDT 2010
>>>>> "Jean-Christophe" == Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com> writes:
Hi,
>> Use a correct udelay value to get bus speed around 100KHz. The udelay
>> value was most likely copied from the older devices, but the 9g45
>> is signicantly faster (400MHz, DDR, ..), so a udelay of 2 gives a
>> bus speed of around 190KHz, which is too fast for some devices.
>> A udelay value of 5 gives a bus speed of around 90KHz here.
>>
>> Signed-off-by: Peter Korsgaard <jacmet at sunsite.dk>
Jean-Christophe> in this case it will be better to overwite it at board
Jean-Christophe> than force it for all of them
You don't expect most 9g45 users will run at 400MHz? It seems pretty
likely to me. In any case, a safe (but somewhat slow) default seems
better than a potentially unsafe one.
Now, I agree that it would be nice to add an interface to tweak this
delay if needed (extra argument to at91_add_device_i2c()?), but that's
next to the discussion about what the default should be.
--
Bye, Peter Korsgaard
More information about the linux-arm-kernel
mailing list