linux-kernel - Re: [PATCH v2 6/6] media: qcom: camss: vfe: Add support for VFE 1080

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Message-ID: <1aa133b9-2a99-47cb-8309-7e49b5dc4f85@oss.qualcomm.com>
Date: Thu, 16 Oct 2025 18:33:10 +0800
From: Hangxiang Ma <hangxiang.ma@....qualcomm.com>
To: Bryan O'Donoghue <bod@...nel.org>,
        Loic Poulain <loic.poulain@....qualcomm.com>,
        Robert Foss
 <rfoss@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Todor Tomov <todor.too@...il.com>,
        Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-i2c@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, aiqun.yu@....qualcomm.com,
        tingwei.zhang@....qualcomm.com, trilok.soni@....qualcomm.com,
        yijie.yang@....qualcomm.com,
        Jingyi Wang <jingyi.wang@....qualcomm.com>,
        Atiya Kailany <atiya.kailany@....qualcomm.com>
Subject: Re: [PATCH v2 6/6] media: qcom: camss: vfe: Add support for VFE 1080

On 10/16/2025 6:09 PM, Bryan O'Donoghue wrote:
> On 15/10/2025 03:56, Hangxiang Ma wrote:
>> +
>> +        /* Deferring the reg update until after CSID config */
>> +        if (!vfe->camss->res->vfe_res[vfe->id].vfe.is_deferred)
>> +            ops->reg_update(vfe, line->id);
>>       }
> 
> But why ?
> 
> ---
> bod

That a story. When testing the RDI path on Kaanapali, we found one image 
buffer starved at 19/20 stage. We want to capture 20 images but only 19 
received.

On Kaanapali, the AUP and RUP are split into two separate registers not 
a single one. Maybe this hardware change impacts something. Calling 
ops->reg_update() in vfe_enable_output_v2 function only applies one 
buffer address. The downstream code defers AUP and RUP to CSID 
configuration stage. We mimic that and find it can solve this issue.

---
Hangxiang