linux-kernel - Re: [PATCH 0/5] clk: qcom: sm8[56]50: Drop the Disp AHB clock from Display Clock Controller

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Message-ID: <ZbI7k+bDy+KSmncq@linaro.org>
Date: Thu, 25 Jan 2024 12:44:35 +0200
From: Abel Vesa <abel.vesa@...aro.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Bjorn Andersson <andersson@...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>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] clk: qcom: sm8[56]50: Drop the Disp AHB clock from
 Display Clock Controller

On 24-01-25 10:49:23, Konrad Dybcio wrote:
> 
> 
> On 1/25/24 10:27, Abel Vesa wrote:
> > The Disp AHB clock is provided by the GCC but never registered. It is
> > instead enabled on probe as it is expected to be always-on. So it should
> > be dropped from Disp CC entirely.
> > 
> > Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> > ---
> 
> Abel, you just raised some concerns over my series doing this and now
> you're doing the same, plus breaking backwards compatibility for no
> good reason, instead of solving the problem.

Sorry but, during the off-list discussion, you convinced me that it is OK to drop
their registration as long as we enable them on probe.

I've not seen the following reply in time before sending current series:
https://lore.kernel.org/all/6aa58497-9727-4601-b6eb-264c478997c3@linaro.org/

Since this is blocking the patches for dispcc and dts for X1E80100, I
thought I'd just drop the clock as required from DT point of view.
But yeah, you're right, it breaks bindings ABI and that's wrong.

> 
> The correct solution here is to register the AHB clock with GCC and
> pm_clk_add() it from dispcc's .probe (and enable runtime PM on dispcc
> if it's already not the case). Then the AHB clock will be gated when
> no display hardware (= no dispcc consumer) is in use.

I agree.

> 
> 8[56]50 are in a good position for this, as they already have the
> required DTS reference. Unfortunately, I still haven't fully dug
> into this for platforms without one, but that's on me.

Since I need to do this for the X1E80100, I'll probably do it for the
other two as well.

Sorry for the misunderstanding.

> 
> Konrad