linux-kernel - Re: [PATCH v6 2/5] dt-bindings: media: Add qcom,x1e80100-camss

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Message-ID: <3kprgpvzffupnjbh2aodsowwklliywpemzwpsftd2cng562yuw@37tpwmpemr2c>
Date: Fri, 25 Apr 2025 11:26:22 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Robert Foss <rfoss@...nel.org>,
        Todor Tomov <todor.too@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
Subject: Re: [PATCH v6 2/5] dt-bindings: media: Add qcom,x1e80100-camss

On Thu, Apr 24, 2025 at 12:51:31PM +0100, Bryan O'Donoghue wrote:
> On 24/04/2025 12:32, Dmitry Baryshkov wrote:
> > On Thu, Apr 24, 2025 at 12:29:39PM +0100, Bryan O'Donoghue wrote:
> > > On 24/04/2025 11:45, Dmitry Baryshkov wrote:
> > > > > Which would then be consistent across SoCs for as long as 0p9 and 1p2 are
> > > > > the power-domains used by these PHYs.
> > > > This won't be consistent with other cases where we have a shared power
> > > > pin. For example, for PMICs we provide supply names which match pin
> > > > names rather than one-supply-per-LDO.
> > > 
> > > Yes but taking a random example from a PMIC vdd-l2-l13-l14-supply is
> > > specific to a given PMIC, so you need to name it specifically wrt its PMIC
> > > pin-name whereas csiphyX-1p2 is there for every CSIPHY we have.
> > 
> > This is fine from my POV.
> > 
> > > For example on qcom2290 there's a shared power-pin for VDD_A_CAMSS_PLL_1P8
> > > but then individual power-pins for VDD_A_CSI_0_1P2 and VDD_A_CSI_1_1P2.
> > 
> > So far so good.
> > 
> > > 
> > > If we follow the general proposal of
> > > 
> > > vdd-csiphyX-1p2-supply
> > > vdd-csiphyX-0p9-supply
> > > 
> > > in the yaml, then whether SoCs like qcm2290 share 1p8 or SoCs like sm8650,
> > > sm8450, x1e have individual 1p8 pins is up to the dtsi to decide.
> > 
> > So, what should be the behaviour if the DT defines different supplies
> > for csiphy0 and csiphy1? Would you express that constraint in DT?
> > 
> 
> You'd have that for qcm2290
> 
> yaml:
> 
> vdd-csiphy0-1p2-supply
> vdd-csiphy1-1p2-supply
> 
> vdd-csiphy0-0p8-supply
> vdd-csiphy1-0p8-supply
> 
> qcm2290-example0.dtsi
> 
> vdd-csiphy0-1p2-supply = <&vreg_1p2_ex0>; <- individual supply in PCB
> vdd-csiphy1-1p2-supply = <&vreg_1p2_ex1>; <- individual supply in PCB
> 
> vdd-csiphy0-0p8-supply = <&vreg_0p9_ex0>; <- shared pin in the SoC
> vdd-csiphy1-0p8-supply = <&vreg_0p9_ex0>; <- shared pin in the SoC

What should driver do if:

vdd-csiphy0-1p2-supply = <&vreg_1p2_ex0>; <- individual supply in PCB
vdd-csiphy1-1p2-supply = <&vreg_1p2_ex1>; <- individual supply in PCB

vdd-csiphy0-0p8-supply = <&vreg_0p9_ex0>; <- shared pin in the SoC
vdd-csiphy1-0p8-supply = <&vreg_0p9_ex1>; <- should be shared pin

I don't want to allow DT authors to make this kind of mistake.

-- 
With best wishes
Dmitry