linux-kernel - Re: [PATCH v3 04/15] clk: qcom: gcc-sm6375: Add runtime PM

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Message-ID: <ZYKzU4FFCc9lnE-p@hovoldconsulting.com>
Date: Wed, 20 Dec 2023 10:26:43 +0100
From: Johan Hovold <johan@...nel.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Andy Gross <agross@...nel.org>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 04/15] clk: qcom: gcc-sm6375: Add runtime PM

On Wed, Dec 20, 2023 at 01:30:45AM +0100, Konrad Dybcio wrote:
> The GCC block on SM6375 is powered by the VDD_CX rail. We need to ensure
> that CX is enabled to prevent unwanted power collapse 

As I pointed out earlier, this bit of the commit message is incorrect
and misleading as the power domain will never be disabled until you
enable runtime PM as part of this very patch:

	https://lore.kernel.org/all/ZLaSpFFBzP_Yz5yY@hovoldconsulting.com/

Specifically, genpd will not power off CX (at runtime) while the driver
is bound when runtime PM is left disabled.

> and that the
> reference is dropped when unused so that the system can enter a
> firmware-managed lower power state.
> 
> Enable runtime PM to keep the power flowing only when necessary.

The rest is correct.

Johan