linux-kernel - Re: [PATCH 07/13] dt-bindings: media: camss: Add qcom,sm8550-camss binding

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Message-ID: <da60cf71-13a4-465d-a0ee-ca2ad3775262@linaro.org>
Date: Thu, 12 Sep 2024 15:44:11 +0300
From: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Depeng Shao <quic_depengs@...cinc.com>, rfoss@...nel.org,
 todor.too@...il.com, mchehab@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org,
 Neil Armstrong <neil.armstrong@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 kernel@...cinc.com, Yongsheng Li <quic_yon@...cinc.com>
Subject: Re: [PATCH 07/13] dt-bindings: media: camss: Add qcom,sm8550-camss
 binding

Hi Bryan.

On 9/12/24 14:41, Bryan O'Donoghue wrote:
> On 12/09/2024 09:22, Vladimir Zapolskiy wrote:
>>> +
>>> +  vdda-phy-supply:
>>> +    description:
>>> +      Phandle to a regulator supply to PHY core block.
>>> +
>>> +  vdda-pll-supply:
>>> +    description:
>>> +      Phandle to 1.2V regulator supply to PHY refclk pll block.
>>> +
>>
>> Here the supplies should be split into ones, which are specific to CSI
>> blocks,
>> and I believe they shall be set as optional.
> 
> In principle I agree with that, each CSIPHY should have its own vdda-phy
> and vdda-pll regulator specified.
> 
> In practice though I don't believe its necessary, below.
> 
>> The proposed names are:
>>
>> vdda-phy-01-supply
>> vdda-pll-01-supply
>> vdda-phy-23-supply
>> vdda-pll-23-supply
>> vdda-phy-46-supply
>> vdda-pll-46-supply
>> vdda-phy-57-supply
>> vdda-pll-57-supply
> 
> In principle, you're right, we need to expand the name set here.
> 
>> I understand that what I ask is much more clumsy, and it could be seen
>> even as
>> unneeded, however it'll be the right set of properties to describe the
>> CAMSS IP
>> in this respect
> I think the following naming would be better as it matches the
> power-grid naming in the docs.
> 
> csiphyX-vdda-phy-supply
> csiphyX-vdda-pll-supply

I have no opinion about the names, any reason for name selection is
good for me.

> =>
> 
> // voltage domain = vdd_a_csi_01_09 = regulator l1e
> csiphy0-vdda-phy-supply = <&vreg_l1e_0p9>;
> 
> // voltage domain = vdd_a_csi_01_1p2 = regulator l3e
> csiphy0-vdda-pll-supply = <&vreg_l3e_1p2>;
> 
> //
> csiphy1-vdda-phy-supply = <&vreg_l1e_0p9>;
> csiphy1-vdda-pll-supply = <&vreg_l3e_1p2>;
> 
> Where X indicates the CSIPHY number.
> 
> So in fact, in practice we don't need to differentiate these entries.
> 
> Checking x1e80100 ...

Checking some particular board, right?

> csiphy0
> 
> vdda-phy-supply = <&vreg_l2c_0p9>;
> vdda-pll-supply = <&vreg_l1c_1p2>;
> 
> This is also the case for csiphy 1/2/4
> 
> So, I _don't_ believe this is work we need to do, since its the same
> regulator for each PHY.

This is board specific, and even if the separation is not needed on the boards
you have just checked, still it may be needed on some boards, which are not yet
checked/not yet known.

It's needed to make the best predictions about all possible usage of hardware,
fortunately it's easy in this particular case, and it's trivial to correct it now
than on some day later on.

--
Best wishes,
Vladimir