linux-kernel - Re: [PATCH v3 07/15] media: qcom: camss: Capture VFE CSID dependency in a helper function

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Message-ID: <bf419311-5931-e8d9-a785-0bf9df3c884d@linaro.org>
Date:   Sat, 26 Aug 2023 13:12:26 +0100
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>, rfoss@...nel.org,
        todor.too@...il.com, agross@...nel.org, andersson@...nel.org,
        mchehab@...nel.org, hverkuil-cisco@...all.nl,
        laurent.pinchart@...asonboard.com, sakari.ailus@...ux.intel.com,
        andrey.konovalov@...aro.org
Cc:     linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 07/15] media: qcom: camss: Capture VFE CSID dependency
 in a helper function

On 26/08/2023 13:04, Konrad Dybcio wrote:
>>>>   From sdm845 onwards we need to ensure the VFE is powered on prior to
>>>> switching on the CSID.
>>> And what's the symptom if we fail to ensure this? How can someone
>>> adding support for another platform tell whether the match-list
>>> should be expanded?
>> That person has to understand the dependency.
> If we need this workaround, there surely must be something that doesn't
> work without it, a measurable symptom. What is it?

The CSID lives inside of the VFE therefore the VFE must be power prior 
to the CSID.

The symptom will be .. the CSID doesn't come out of reset.

---
bod