linux-kernel - Re: [PATCH v4 1/4] firmware: arm_scmi: Add polling support for completion in smc

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Message-ID: <1c58a05b-1337-0287-225f-5a73b4c6828e@quicinc.com>
Date:   Tue, 3 Oct 2023 08:53:20 -0700
From:   Nikunj Kela <quic_nkela@...cinc.com>
To:     Sudeep Holla <sudeep.holla@....com>
CC:     <cristian.marussi@....com>, <robh+dt@...nel.org>,
        Brian Masney <bmasney@...hat.com>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <andersson@...nel.org>, <konrad.dybcio@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v4 1/4] firmware: arm_scmi: Add polling support for
 completion in smc


On 10/3/2023 3:33 AM, Sudeep Holla wrote:
> On Mon, Sep 11, 2023 at 12:43:56PM -0700, Nikunj Kela wrote:
>> Currently, the return from the smc call assumes the completion of
>> the scmi request. However this may not be true in virtual platforms
>> that are using hvc doorbell.
>>
> Hmm, it is expectation from SMCCC for the fast calls. Is you HVC FID
> not a fast call. AFAIK, only TOS use yielding calls. Are you using them
> here ? If not, this must complete when the SMC/HVC returns. We added
> support for platforms indicating the same via interrupt.
>
> I would like to avoid adding this build config. Why does it require polling ?
> Broken firmware ? I would add a compatible for that. Or if the qcom always
> wants to do this way, just make it specific to the qcom compatible.
>
> I would avoid a config flag as it needs to be always enabled for single
> image and affects other platforms as well. So please drop this change.
> If this is absolutely needed, just add additional property which DT
> maintainers may not like as it is more like a policy or just make it
> compatible specific.
>
> --
> Regards,
> Sudeep
We are using Fast call FID. We are using completion IRQ for all the scmi 
instances except one where we need to communicate with the server when 
GIC is in suspended state in HLOS. We will need to poll the channel for 
completion in that use case. I am open to suggestions.