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SubjectRe: [PATCH v2 2/5] cpu_pm: call notifiers during suspend
Date
Santosh Shilimkar <santosh.shilimkar@ti.com> writes:

> From: Colin Cross <ccross@android.com>
>
> Implements syscore_ops in cpu_pm to call the cpu and
> cpu cluster notifiers during suspend and resume,
> allowing drivers receiving the notifications to
> avoid implementing syscore_ops.
>
> Signed-off-by: Colin Cross <ccross@android.com>
> [santosh.shilimkar@ti.com: Rebased against 3.1-rc4]
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>

I don't think using syscore_ops is right here. The platform code should
decide where in its own suspend path the notifiers should be triggered.

The reason is because while the syscore_ops run late in the suspend
path, they still run before some platform-specific decisions about the
low-power states are made. That means that any notifiers that need to
use information about the target low-power state (e.g. whether context
will be lost or not) cannot do so since that information has not yet
been decided until the platform_suspend_ops->enter() runs.

Basically, I think the cpu_*_pm_enter() calls should be called by
platform-specific code, not by common code.

Kevin

> ---
> kernel/cpu_pm.c | 33 +++++++++++++++++++++++++++++++++
> 1 files changed, 33 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c
> index 54aa892..3d115d0 100644
> --- a/kernel/cpu_pm.c
> +++ b/kernel/cpu_pm.c
> @@ -20,6 +20,7 @@
> #include <linux/module.h>
> #include <linux/notifier.h>
> #include <linux/spinlock.h>
> +#include <linux/syscore_ops.h>
>
> static DEFINE_RWLOCK(cpu_pm_notifier_lock);
> static RAW_NOTIFIER_HEAD(cpu_pm_notifier_chain);
> @@ -113,3 +114,35 @@ int cpu_cluster_pm_exit(void)
> return ret;
> }
> EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
> +
> +#ifdef CONFIG_PM
> +static int cpu_pm_suspend(void)
> +{
> + int ret;
> +
> + ret = cpu_pm_enter();
> + if (ret)
> + return ret;
> +
> + ret = cpu_cluster_pm_enter();
> + return ret;
> +}
> +
> +static void cpu_pm_resume(void)
> +{
> + cpu_cluster_pm_exit();
> + cpu_pm_exit();
> +}
> +
> +static struct syscore_ops cpu_pm_syscore_ops = {
> + .suspend = cpu_pm_suspend,
> + .resume = cpu_pm_resume,
> +};
> +
> +static int cpu_pm_init(void)
> +{
> + register_syscore_ops(&cpu_pm_syscore_ops);
> + return 0;
> +}
> +core_initcall(cpu_pm_init);
> +#endif


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