linux-kernel - Re: [PATCH v3 10/23] media: iris: Track flush responses to prevent premature completion

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Message-ID: <56c87a9a-0f7e-7d1a-af27-d70d46b50b41@quicinc.com>
Date: Fri, 2 May 2025 19:11:33 +0530
From: Dikshita Agarwal <quic_dikshita@...cinc.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Vikash Garodia
	<quic_vgarodia@...cinc.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        Stefan Schmidt
	<stefan.schmidt@...aro.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        "Bjorn
 Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        "Rob Herring" <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        "Conor Dooley" <conor+dt@...nel.org>
CC: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Neil Armstrong
	<neil.armstrong@...aro.org>,
        Nicolas Dufresne
	<nicolas.dufresne@...labora.com>,
        <linux-media@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <20250417-topic-sm8x50-iris-v10-v7-0-f020cb1d0e98@...aro.org>,
        <20250424-qcs8300_iris-v5-0-f118f505c300@...cinc.com>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v3 10/23] media: iris: Track flush responses to prevent
 premature completion



On 5/2/2025 6:10 PM, Bryan O'Donoghue wrote:
> On 01/05/2025 20:13, Dikshita Agarwal wrote:
>> Currently, two types of flush commands are queued to the firmware,
>> the first flush queued as part of sequence change, does not wait for a
>> response, while the second flush queued as part of stop, expects a
>> completion response before proceeding further.
>>
>> Due to timing issue, the flush response corresponding to the first
>> command could arrive after the second flush is issued. This casuses the
>> driver to incorrectly assume that the second flush has completed,
>> leading to the premature signaling of flush_completion.
>>
>> To address this, introduce a counter to track the number of pending
>> flush responses and signal flush completion only when all expected
>> responses are received.
> 
> Is there no other way to correlate command/response than a counter on the
> APSS side ?
> 
> Usually command/response protocols have some kind of identifier field or
> sequence number embedded in the protocol headers.
> 
There is no such identifier field for flush command and response at the moment.

Thanks,
Dikshita
> ---
> bod