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

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Date: Thu, 25 Jan 2024 10:49:23 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Abel Vesa <abel.vesa@...aro.org>, 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>
Cc: 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 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.

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.

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.

Konrad