linux-kernel - Re: [PATCH v5 02/13] dt-bindings: remoteproc: qcom: pas: Add QMP property

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Message-ID: <5848670f513187734d7625f242bbf67b@codeaurora.org>
Date:   Mon, 23 Aug 2021 21:49:08 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     bjorn.andersson@...aro.org, mka@...omium.org, robh+dt@...nel.org,
        ulf.hansson@...aro.org, rjw@...ysocki.net, agross@...nel.org,
        ohad@...ery.com, mathieu.poirier@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        dianders@...omium.org, rishabhb@...eaurora.org,
        sidgup@...eaurora.org
Subject: Re: [PATCH v5 02/13] dt-bindings: remoteproc: qcom: pas: Add QMP
 property

On 2021-08-21 23:47, Stephen Boyd wrote:
> Quoting Sibi Sankar (2021-08-20 07:24:02)
>> On 2021-08-20 00:25, Stephen Boyd wrote:
>> > Quoting Sibi Sankar (2021-08-18 20:02:05)
>> >> The load state power-domain, used by the co-processors to notify the
>> >> Always on Subsystem (AOSS) that a particular co-processor is up/down,
>> >> suffers from the side-effect of changing states during suspend/resume.
>> >> However the co-processors enter low-power modes independent to that of
>> >> the application processor and their states are expected to remain
>> >> unaltered across system suspend/resume cycles. To achieve this
>> >> behavior
>> >> let's drop the load state power-domain and replace them with the qmp
>> >> property for all SoCs supporting low power mode signalling.
>> >>
>> >
>> > How do we drop the load state property without breaking existing DTBs?
>> > Maybe we need to leave it there and then somehow make it optional? Or
>> > do
>> > we not care about this problem as the driver will start ignoring it?
>> 
>> We can afford to break the bindings
>> because of the following reason:
>> 
>> * Load state in mainline is currently
>>    broken i.e. it doesn't serve its
>>    main purpose of signalling AOP of
>>    the correct state of Q6 during
>>    system suspend/resume. Thus we
>>    can maintain current functionality
>>    even without the load state votes
>>    i.e. when a new kernel with load
>>    state removed is used with an older
>>    dtb the remoteproc functionality
>>    will remain the same.
>> 
> 
> Alright. Is that reflected somewhere in the commit text? I must have
> missed it. Can you please add it?

Commit message throughout the series
mention that the current load state
implementation is broken but it is
never mentioned explicitly that it
is the reason why bindings can be
broken. I'll wait for a couple of
days to see if I get any more
comments and will re-word it in the
next re-spin.

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