Re: [PATCH v7 1/3] irqchip/gic-v3-its: add ability to save/restore ITS state

[Mark Rutland]

On Wed, Feb 28, 2018 at 09:48:18PM -0800, Derek Basehore wrote:
> Some platforms power off GIC logic in suspend, so we need to
> save/restore state. The distributor and redistributor registers need
> to be handled in platform code due to access permissions on those
> registers, but the ITS registers can be restored in the kernel.
> 
> Signed-off-by: Derek Basehore <dbasehore@xxxxxxxxxxxx>

How much state do we have to save/restore?

Given we can apparently read all this state, couldn't we *always* save
the state, then upon resume detect if the state has been lost, restoring
it if so?

That way, we don't need a property in FW tables for DT or ACPI.

[...]

> @@ -3261,6 +3363,9 @@ static int __init its_probe_one(struct resource *res,
>  		ctlr |= GITS_CTLR_ImDe;
>  	writel_relaxed(ctlr, its->base + GITS_CTLR);
>  
> +	if (fwnode_property_present(handle, "reset-on-suspend"))
> +		its->flags |= ITS_FLAGS_SAVE_SUSPEND_STATE;

Does this allow this property on an ACPI system?

If we need this on ACPI, we need a spec update to handle this properly,
and shouldn't use device properties like this.

Thanks,
Mark.