On Fri, Jun 29, 2012 at 10:52 PM, Jon Hunter <jon-hunter@xxxxxx> wrote: > 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. Indeed. GPIO driver should not assume the value. > 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. Make sense too. > 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 > 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 Jon for sorting this out. Patch looks good to me. Reviewed-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx> -- 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
