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

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Message-ID: <20230828194010.GF17083@pendragon.ideasonboard.com>
Date:   Mon, 28 Aug 2023 22:40:10 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc:     rfoss@...nel.org, todor.too@...il.com, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org, mchehab@...nel.org,
        hverkuil-cisco@...all.nl, sakari.ailus@...ux.intel.com,
        andrey.konovalov@...aro.org, 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 Mon, Aug 28, 2023 at 08:37:44PM +0100, Bryan O'Donoghue wrote:
> On 28/08/2023 19:47, Laurent Pinchart wrote:
> > Hi Bryan,
> > 
> > Thank you for the patch.
> > 
> > On Wed, Aug 23, 2023 at 11:44:36AM +0100, Bryan O'Donoghue wrote:
> >>  From sdm845 onwards we need to ensure the VFE is powered on prior to
> >> switching on the CSID.
> > 
> > Based on the discussions with Konrad in the mail thread, I would record
> > here the reason for this requirement.
> > 
> > What happens if you unconditionally power up the VFE prior to switching
> > the CSID on ? Will this break something on platforms older than SDM845 ?
> 
> vfe->power_count will bump and you will be fine.

Then maybe that would be a simpler solution than having a
device-specific power sequence ?

-- 
Regards,

Laurent Pinchart