On 12/20/2012 11:36 PM, Joseph Lo wrote: > On Fri, 2012-12-21 at 01:43 +0800, Stephen Warren wrote: >> On 12/17/2012 07:30 PM, Joseph Lo wrote: >>> The powered-down state of Tegra20 requires power gating both CPU cores. >>> When the secondary CPU requests to enter powered-down state, it saves >>> its own contexts and then enters WFI. The Tegra20 had a limition to >>> power down both CPU cores. The secondary CPU must waits for CPU0 in >>> powered-down state too. If the secondary CPU be woken up before CPU0 >>> entering powered-down state, then it needs to restore its CPU states >>> and waits for next chance. >>> >>> Be aware of that, you may see the legacy power state "LP2" in the code >>> which is exactly the same meaning of "CPU power down". >>> diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c [ code to set up the idle state array] >> ... although I personally much preferred when all this was just static >> initialization directly in tegra_idle_driver, rather than all this messy >> copying. Really, struct cpuidle_driver should point at the array, rather >> than including it. >> > I think so. If you strongly prefer the original style, I can rollback to > the previous version here. I suppose there's little point changing it back; I know others objected to the original code:-( >>> diff --git a/arch/arm/mach-tegra/pm.c b/arch/arm/mach-tegra/pm.c >> >>> @@ -173,6 +173,8 @@ bool __cpuinit tegra_set_cpu_in_lp2(int phy_cpu_id) >>> >>> if ((phy_cpu_id == 0) && cpumask_equal(cpu_lp2_mask, cpu_online_mask)) >>> last_cpu = true; >>> + else if (phy_cpu_id == 1) >>> + tegra20_cpu_set_resettable_soon(); >>> >>> spin_unlock(&tegra_lp2_lock); >>> return last_cpu; >> >> Shouldn't the code in that else branch have a run-time check for whether >> it's running on Tegra20? When compiled without Tegra20 support, >> tegra20_cpu_set_resettable_soon() is a dummy static inline, but when >> both Tegra20 and Tegra30 are compiled in, isn't that code going to run >> when it shouldn't; pm.c being a common file. > > Because the code didn't hurt Tegra30, so I didn't add a runtime > detection there. If you have concern, I can add runtime detection there. The only issue I see that could happen is that tegra20_cpu_set_resettable_soon() writes to some location to maintain the CPU resettable state. Since I assume that location isn't used for that purpose on Tegra30, could this cause some conflict? It seems best to add the check to make sure there's no issue here. -- 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
