On Wed, 2012-05-02 at 10:45 +0200, Bedia, Vaibhav wrote: > Hi Tero, > > On Fri, Apr 20, 2012 at 14:49:49, Kristo, Tero wrote: > > From: Axel Haslam <axelhaslam@xxxxxxxxx> > > > > On OMAP4, there is no support to read previous logic state > > or previous memory state achieved when a power domain transitions > > to RET. Instead there are module level context registers. > > > > In order to support the powerdomain level logic/mem_off_counters > > on OMAP4, instead use the previous power state achieved (RET) and > > the *programmed* logic/mem RET state to derive if a powerdomain lost > > logic or did not. > > > > If the powerdomain is programmed to enter RET state and lose logic > > in RET state, knowing that the powerdomain entered RET is good enough > > to derive that the logic was lost as well, in such cases. > > > > Unfortunately this won't scale for AM33xx devices :( > It neither has module level context registers nor previous logic/memory state > registers in PRCM. > > At a top level, there's a Cortex-M3 (CM3) to assist the low power state transitions > and the indication of successful transition to a low power states is handled as part > of the IPC mechanism between the MPU (A8) and CM3 which is s/w defined. > > Since the various APIs like omap_hwmod_get_context_loss_context() and friends are > necessary to have correct context saves and restores in drivers we'll need > to add another API for AM33xx which basically builds on the IPC mechanism > and updates the counters. > > So, instead of the fallback mechanism that is currently in place, can the > implementation for updating the logic/mem counters be converted to make use of > function pointers. When AM33xx PM support comes in, we can just define > a custom function and not pollute the code with cpu_is_* checks. I think that should be fine. We can add arch_hwmod struct or such (similar to arch_clkdm / arch_pwrdm) if need be. However, I think we should just expand the support towards that way once we can implement the am33xx support properly with a separate patch. I guess this doesn't break anything on am33xx currently, right? -Tero -- 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
