linux-kernel - Re: [PATCH 1/3] dt-bindings: arm,psci: Allow S2RAM power

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Message-ID: <Z1LQOmEfFy640PjG@bogus>
Date: Fri, 6 Dec 2024 10:21:46 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Konrad Dybcio <konradybcio@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
	Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH 1/3] dt-bindings: arm,psci: Allow S2RAM power_state
 parameter description

On Mon, Oct 28, 2024 at 03:22:57PM +0100, Konrad Dybcio wrote:
> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> 
> Certain firmware implementations (such as the ones found on Qualcomm
> SoCs between roughly 2015 and 2023) expose an S3-like S2RAM state
> through the CPU_SUSPEND call, as opposed to exposing PSCIv1.0's
> optional PSCI_SYSTEM_SUSPEND.
>

If so, can you elaborate why s2idle doesn't work as an alternative to what
you are hacking up here.

> This really doesn't work well with the model where we associate all
> calls to CPU_SUSPEND with cpuidle. Allow specifying a single special
> CPU_SUSPEND suspend parameter value that is to be treated just like
> SYSTEM_SUSPEND from the OS's point of view.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> ---
>  Documentation/devicetree/bindings/arm/psci.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/arm/psci.yaml b/Documentation/devicetree/bindings/arm/psci.yaml
> index cbb012e217ab80c1ca88e611e7acc06c6d56fad0..a6901878697c8e1ec1cbfed62298ae3bc58f2501 100644
> --- a/Documentation/devicetree/bindings/arm/psci.yaml
> +++ b/Documentation/devicetree/bindings/arm/psci.yaml
> @@ -98,6 +98,12 @@ properties:
>        [1] Kernel documentation - ARM idle states bindings
>          Documentation/devicetree/bindings/cpu/idle-states.yaml
>  
> +  arm,psci-s2ram-param:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      power_state parameter denoting the S2RAM/S3-like system suspend state

Yet another NACK as this corresponds to PSCI SYSTEM_SUSPEND and as per
specification it takes no such parameter. This is just misleading.

-- 
Regards,
Sudeep