[PATCH 03/17] ARM: gic: Use cpu pm notifiers to save gic state

[Santosh Shilimkar]

On 7/7/2011 8:50 AM, Lorenzo Pieralisi wrote:
> From: Colin Cross<ccross at android.com>
>
> When the cpu is powered down in a low power mode, the gic cpu
> interface may be reset, and when the cpu complex is powered
> down, the gic distributor may also be reset.
>
> This patch uses CPU_PM_ENTER and CPU_PM_EXIT notifiers to save
> and restore the gic cpu interface registers, and the
> CPU_COMPLEX_PM_ENTER and CPU_COMPLEX_PM_EXIT notifiers to save
> and restore the gic distributor registers.
>
> Signed-off-by: Colin Cross<ccross at android.com>
> ---
>   arch/arm/common/gic.c |  212 +++++++++++++++++++++++++++++++++++++++++++++++++
>   1 files changed, 212 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/common/gic.c b/arch/arm/common/gic.c
> index 4ddd0a6..8d62e07 100644
> --- a/arch/arm/common/gic.c
> +++ b/arch/arm/common/gic.c

[...]

> +
> +static int gic_notifier(struct notifier_block *self, unsigned long cmd,	void *v)
> +{
> +	int i;
> +
> +	for (i = 0; i<  MAX_GIC_NR; i++) {
> +		switch (cmd) {
> +		case CPU_PM_ENTER:
> +			gic_cpu_save(i);
> +			break;
> +		case CPU_PM_ENTER_FAILED:
> +		case CPU_PM_EXIT:
> +			gic_cpu_restore(i);
> +			break;
> +		case CPU_COMPLEX_PM_ENTER:
> +			gic_dist_save(i);
> +			break;
> +		case CPU_COMPLEX_PM_ENTER_FAILED:
> +		case CPU_COMPLEX_PM_EXIT:
> +			gic_dist_restore(i);
> +			break;
> +		}
> +	}
> +
> +	return NOTIFY_OK;
> +}

Just to put forth OMAP requirements for GIC and see how much
we can leverage these for OMAP.

OMAP support GP(general) and HS(secure) devices and implements
the trustzone on these devices. on Secure devices the GIC save
and restore is completely done by secure ROM code. There are
API's for save and restore is automatic on CPU reset based
on the last CPU cluster state.

On GP devices too, very few GIC registers needs to be saved
in a pre-defined memory/register layout and restore is again
done by boot-ROM code.

OMAP need to enable/disable distributor and CPU interfaces
based on CPU power states and that is something can be useful.
Would be good if there is a provision to over-write the gic
save/restore function using function pointers so that OMAP
PM code can use the notifiers.

Any more thoughts how we can handle this? We would like to
use common ARM code as much as possible.

Regards
Santosh