[PATCH V3 5/5] ARM: tegra20: cpuidle: apply coupled cpuidle for powered-down mode
From: Stephen Warren <hidden>
Date: 2012-12-20 17:54:09
Also in:
linux-tegra
On 12/17/2012 07:31 PM, Joseph Lo wrote:
The "powered-down" cpuidle mode of Tegra20 needs the CPU0 be the last one core to go into this mode before other core. The coupled cpuidle framework can help to sync the MPCore to coupled state then go into "powered-down" idle mode together. The driver can just assume the MPCore come into "powered-down" mode at the same time. No need to take care if the CPU_0 goes into this mode along and only can put it into safe idle mode (WFI). 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 for waiting CPU0 in the same state. When the CPU0 requests powered-down state, it attempts to put the secondary CPU into reset to prevent it from waking up. Then power down both CPUs together and power off the cpu rail. 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".
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diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c
+static void tegra20_wake_reset_cpu_1(void)
Nit/bikeshe: I think tegra20_wake_from_reset_cpu_1() might be a slightly more descriptive name? I assume the function works on CPU1, which is assumed to be in reset, and removes reset from the CPU so it boots.
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@@ -137,6 +241,9 @@ int __init tegra20_cpuidle_init(void) for_each_possible_cpu(cpu) { dev = &per_cpu(tegra_idle_device, cpu); dev->cpu = cpu; +#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED + dev->coupled_cpus = *cpu_online_mask; +#endif
That CONFIG option is selected by ARCH_TEGRA_2x_SOC, which must be enabled for this file to be compiled. So, you can drop the ifdef, and make the code uncondtional.