On 07/02/2012 07:05 PM, Kevin Hilman wrote: > NeilBrown <neilb@xxxxxxx> writes: > >> On Mon, 2 Jul 2012 13:26:38 -0500 Jon Hunter <jon-hunter@xxxxxx> wrote: >> >>> >>> On 07/02/2012 01:07 PM, Kevin Hilman wrote: >>>> + Neil Brown >>>> >>>> Hi Jon, >>>> >>>> Jon Hunter <jon-hunter@xxxxxx> writes: >>>> >>>>> Currently the gpio _runtime_resume/suspend functions are calling the >>>>> get_context_loss_count() platform function if the function is populated for >>>>> a gpio bank. This function is used to determine if the gpio bank logic state >>>>> needs to be restored due to a power transition. This function will be populated >>>>> for all banks, but it should only be called for banks that have the >>>>> "loses_context" variable set. It is pointless to call this if loses_context is >>>>> false as we know the context will never be lost and will not need restoring. >>>>> >>>>> For all OMAP2+ devices gpio bank-0 is in an always-on power domain and so will >>>>> never lose context. We found that the get_context_loss_count() was being called >>>>> for bank-0 during the probe and returning 1 instead of 0 indicating that the >>>>> context had been lost. This was causing the context restore function to be >>>>> called at probe time for this bank and because the context had never been saved, >>>>> was restoring an invalid state. This ultimately resulted in a crash [1]. >>>>> >>>>> There are multiple bugs here that need to be addressed ... >>>>> >>>>> 1. Why the always-on power domain returns a context loss count of 1? This needs >>>>> to be fixed in the power domain code. However, the gpio driver should not >>>>> assume the loss count is 0 to begin with. >>>>> 2. The omap gpio driver should never be calling get_context_loss_count for a >>>>> gpio bank in a always-on domain. This is pointless and adds unneccessary >>>>> overhead. >>>>> 3. The OMAP gpio driver assumes that the initial power domain context loss count >>>>> will be 0 at the time the gpio driver is probed. However, it could be >>>>> possible that this is not the case and an invalid context restore could be >>>>> performed during the probe. To avoid this otherwise only populated the >>>> >>>> The 'To avoid this...' sentence here doesn't read well. Looks like you >>>> need to: >>>> >>>> s/otherwise// >>> >>> Yes, I meant to have dropped "otherwise" here. Thanks! >>> >>>> s/populated/populate/ >>> >>> Yes that too! I must have re-worded and screwed it up royally :-( >>> >>>> ? >>>> >>>>> get_context_loss_count() function pointer after the initial call to >>>>> pm_runtime_get() has occurred. This will ensure that the first >>>>> pm_runtime_put() initialised the loss count correctly. >>>>> >>>>> This patch addresses issues 2 and 3 above. >>>>> [1] http://marc.info/?l=linux-omap&m=134065775323775&w=2 >>>>> >>>>> Cc: Grant Likely <grant.likely@xxxxxxxxxxxx> >>>>> Cc: Linus Walleij <linus.walleij@xxxxxxxxxxxxxx> >>>>> Cc: Kevin Hilman <khilman@xxxxxx> >>>>> Cc: Tarun Kanti DebBarma <tarun.kanti@xxxxxx> >>>>> Cc: Franky Lin <frankyl@xxxxxxxxxxxx> >>>>> >>>>> Reported-by: Franky Lin <frankyl@xxxxxxxxxxxx> >>>>> Signed-off-by: Jon Hunter <jon-hunter@xxxxxx> >>>> >>>> Thanks for digging inot this bug Jon. The same bug was brought up by >>>> Neil Brown (Cc'd) in a different thread. >>>> >>>> Neil, it looks to me that this fix will address the problems you were >>>> seeing as well. Care to test, and respond with your ack/tested-by if it >>>> works for you? Thanks. >>> >>> Neil let me know your thoughts and if you are ok, I can clean-up the >>> changelog and re-send. >> >> Yes, works for me and looks sensible. >> >> Tested-by: NeilBrown <neilb@xxxxxxx> >> > > Great! Thanks for testing. > > Jon, please make the minor changelog edits, collect the reviewed-by and > tested-by tags and repost. I'll then queue this up for Grant. Ok, will do that tomorrow. > Based on your earlier comments, this only affects v3.5, so no > need to push it into stable, correct? As far as I can tell. However, not sure if any of the other fixes should be back ported. Cheers Jon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
