* Shilimkar, Santosh <santosh.shilimkar@xxxxxx> [120629 21:23]: > 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. Should this one be Cc: stable? If this is a regression, then the regression causing commit should be mentioned. Tony -- 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
