linux-kernel - Re: [PATCH v2 2/5] media: qcom: camss: Convert to per-VFE pointer for power-domain linkages

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Date:   Fri, 27 Oct 2023 10:38:25 +0100
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>, hverkuil-cisco@...all.nl,
        laurent.pinchart@...asonboard.com, rfoss@...nel.org,
        todor.too@...il.com, andersson@...nel.org, mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] media: qcom: camss: Convert to per-VFE pointer for
 power-domain linkages

On 27/10/2023 10:10, Bryan O'Donoghue wrote:
> power-domains = <VFE_0>,
>                  <VFE_1>,
>                  <TITAN_TOP>; // the controller pd
> 
> vfe-set = <VFE_0>, // has its own PD vfe->id = 0
>            <VFE_1>, // has its own PD vfe->id = 1
>            <VFE_LITE_N>; // has no PD vfe->id = 2
> 
> The basic problem this series fixes is magic indexing.

So be a little clearer; this would be an invalid declaration in dtsi 
right now

power-domains = <TITAN_TOP>, // has to come last
                 <VFE_0>,
                 <VFE_1>; // the code would think this TOP

The TOP GDSC must come last.

Similarly this would an invalid declaration in our resource structure

vfe-set = <VFE_LITE_0>, //the code thinks this is a VFE
           <VFE_LITE_1>, //the code thinks this is a VFE
           <VFE_0>,
           <VFE_1>; // and that this is VFE Lite

vfe_num = 2;
vfe-id = {0..3}

// don't hook a PD for VFE Lite
if (vfe->id >= camss->res->vfe_num)
     return 0;

has_pd fixes checks like that. Eventually we will throw away has_pd when 
legacy indexing is dropped - in which case if vfe->id has a res->pd_name 
we hook it, if not, then not.

The order of declaration won't matter.

---
bod