On Wed, 2012-12-19 at 03:36 +0800, Colin Cross wrote: > On Tue, Dec 18, 2012 at 2:15 AM, Peter De Schrijver > <pdeschrijver@xxxxxxxxxx> wrote: > > On Tue, Dec 18, 2012 at 03:42:24AM +0100, Colin Cross wrote: > >> On Mon, Dec 17, 2012 at 6:30 PM, Joseph Lo <josephl@xxxxxxxxxx> wrote: > >> > The "powered-down" CPU idle mode of Tegra cut off the vdd_cpu rail, it > >> > include the power of GIC. That caused the SGI (Software Generated > >> > Interrupt) been lost. Because the SGI can't wake up the CPU that in > >> > the "powered-down" CPU idle mode. We need to check if there is any > >> > pending SGI when go into "powered-down" CPU idle mode. This is important > >> > especially when applying the coupled cpuidle framework into "power-down" > >> > cpuidle dirver. Because the coupled cpuidle framework may have the > >> > chance that misses IPI_SINGLE_FUNC handling sometimes. > >> > >> This problem exists for any GIC-based SoC, and needs to be fixed in > >> gic_cpu_save or gic_dist_save, whichever one loses the interrupt. > > > > Not necessarily. It depends on the SoC design. On Tegra20, the entire CPU > > cluster is railgated, including the GIC. This causes a pending IPI to be lost. > > But for example on OMAP4, only the actual CPU cores are powergated. The GIC > > stays alive until also the core domain hits idle. By that time a potential > > pending IPI has long woken up the target CPU again, so no additional > > checks are needed for functional correct behavior. > > I'm not sure that is correct for OMAP4. C2 and C3 will put the power > rail for the GIC in retention, and I don't think an IPI will wake it > up. I believe the same problem also exists for Exynos5. In any case, > checking for an IPI early during idle and aborting won't hurt those > platforms, so I still think it should be in the GIC driver and not by > mapping the GIC registers into a separate driver. Hi Colin, If I move this code into common GIC driver, should I just take care pending SGI also? I will try to create a RFC patch for this. Thanks, Joseph -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
