linux-kernel - Re: [PATCH V3 0/4] firmware: arm

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Message-ID: <c8e7420b-a7b4-89cd-1b6e-c1f6693c062d@quicinc.com>
Date: Fri, 25 Oct 2024 11:38:36 +0530
From: Sibi Sankar <quic_sibis@...cinc.com>
To: Johan Hovold <johan@...nel.org>
CC: <sudeep.holla@....com>, <cristian.marussi@....com>,
        <ulf.hansson@...aro.org>, <jassisinghbrar@...il.com>,
        <linux-kernel@...r.kernel.org>, <arm-scmi@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>, <konradybcio@...nel.org>,
        <linux-pm@...r.kernel.org>, <tstrudel@...gle.com>, <rafael@...nel.org>
Subject: Re: [PATCH V3 0/4] firmware: arm_scmi: Misc Fixes



On 10/23/24 21:56, Johan Hovold wrote:
> On Wed, Oct 23, 2024 at 01:16:47PM +0530, Sibi Sankar wrote:
>> On 10/10/24 20:32, Johan Hovold wrote:
>>> On Mon, Oct 07, 2024 at 11:36:38AM +0530, Sibi Sankar wrote:
>>>> The series addresses the kernel warnings reported by Johan at [1] and are
>>>> are required to X1E cpufreq device tree changes [2] to land.
>>>>
>>>> [1] - https://lore.kernel.org/lkml/ZoQjAWse2YxwyRJv@hovoldconsulting.com/
>>>> [2] - https://lore.kernel.org/lkml/20240612124056.39230-1-quic_sibis@quicinc.com/
>>>>
>>>> The following warnings remain unadressed:
>>>> arm-scmi arm-scmi.0.auto: Failed to add opps_by_lvl at 3417600 for NCC - ret:-16
>>>> arm-scmi arm-scmi.0.auto: Failed to add opps_by_lvl at 3417600 for NCC - ret:-16
>>>
>>> Are there any plans for how to address these?
> 
>> Sorry missed replying to this. The error implies that duplicate
>> opps are reported by the SCP firmware and appear once during probe.
> 
> I only see it at boot, but it shows up four times here with the CRD:

https://lore.kernel.org/lkml/d54f6851-d479-a136-f747-4c0180904a5e@quicinc.com/

As explained ^^, we see duplicates for max sustainable performance twice
for each domain.

> 
> [    8.098452] arm-scmi arm-scmi.0.auto: Failed to add opps_by_lvl at 3417600 for NCC - ret:-16
> [    8.109647] arm-scmi arm-scmi.0.auto: Failed to add opps_by_lvl at 3417600 for NCC - ret:-16
> [    8.128970] arm-scmi arm-scmi.0.auto: Failed to add opps_by_lvl at 3417600 for NCC - ret:-16
> [    8.142455] arm-scmi arm-scmi.0.auto: Failed to add opps_by_lvl at 3417600 for NCC - ret:-16
> 
>> This particular error can be fixed only by a firmware update and you
>> should be able to test it out soon on the CRD first.
> 
> Can you explain why this can only be fixed by a firmware update? Why
> can't we suppress these warnings as well, like we did for the other
> warnings related to the duplicate entries?
> 
> IIUC the firmware is not really broken, but rather describes a feature
> that Linux does not (yet) support, right?

We keep saying it's a buggy firmware because the SCP firmware reports
identical perf and power levels for the additional two opps and the
kernel has no way of treating it otherwise and we shouldn't suppress
them. Out of the two duplicate opps reported one is a artifact from how
Qualcomm usually show a transition to boost frequencies. The second opp
which you say is a feature should be treated as a boost opp i.e. one
core can run at max at a lower power when other cores are at idle but
we can start marking them as such once they start advertising their
correct power requirements. So I maintain that this is the best we
can do and need a firmware update for us to address anything more.

-Sibi


> 
> Johan