linux-kernel - Re: [PATCH v7 2/3] DT/arm,gic-v3-its: add reset-on-suspend property

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Message-ID: <20180301113457.jg256bsepf7ggx6v@lakrids.cambridge.arm.com>
Date:   Thu, 1 Mar 2018 11:34:57 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Derek Basehore <dbasehore@...omium.org>
Cc:     linux-kernel@...r.kernel.org, Soby.Mathew@....com,
        sudeep.holla@....com, devicetree@...r.kernel.org,
        robh+dt@...nel.org, linux-pm@...r.kernel.org,
        rafael.j.wysocki@...el.com, tglx@...utronix.de,
        briannorris@...omium.org, marc.zyngier@....com
Subject: Re: [PATCH v7 2/3] DT/arm,gic-v3-its: add reset-on-suspend property

On Wed, Feb 28, 2018 at 09:48:19PM -0800, Derek Basehore wrote:
> This adds documentation for the new reset-on-suspend property. This
> property enables saving and restoring the ITS for when it loses state
> in system suspend.
> 
> Signed-off-by: Derek Basehore <dbasehore@...omium.org>
> ---
>  .../devicetree/bindings/interrupt-controller/arm,gic-v3.txt  | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
> index 0a57f2f4167d..dfd1b9b838cd 100644
> --- a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
> +++ b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
> @@ -78,6 +78,11 @@ These nodes must have the following properties:
>  Optional:
>  - socionext,synquacer-pre-its: (u32, u32) tuple describing the untranslated
>    address and size of the pre-ITS window.
> +- reset-on-suspend: Boolean property. Indicates that the ITS loses power
> +  on suspend to memory (via PSCI_SYSTEM_SUSPEND). Registers and data within
> +  the ITS will be the same as before probe (PSCI FW does not restore state).

What does 'before probe' mean? Perhaps 'at reset'?

Is the state well-defined, or might there be some bits that differ from
boot-to-boot?

Otherwise, this generally looks ok.

> +  Any state stored in external memory is maintained (such as collection
> +  tables stored in external memory).

This a property of PSCI_SYSTEM_SUSPEND not corrupting memory state, so
this need not be stated here. This can go.

Thanks,
Mark.