linux-kernel - Re: [PATCH 4/4] arm64: dts: qcom: sm8350: Fixup the cpufreq node

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Date:   Mon, 30 Aug 2021 12:17:35 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Matthias Kaehlcke <mka@...omium.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     sboyd@...nel.org, robh+dt@...nel.org, viresh.kumar@...aro.org,
        agross@...nel.org, rjw@...ysocki.net,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dianders@...omium.org, tdas@...eaurora.org
Subject: Re: [PATCH 4/4] arm64: dts: qcom: sm8350: Fixup the cpufreq node

On 2021-08-05 05:28, Matthias Kaehlcke wrote:
> On Wed, Aug 04, 2021 at 05:59:04PM -0500, Bjorn Andersson wrote:
>> On Thu 29 Jul 13:04 CDT 2021, Sibi Sankar wrote:
>> 
>> > Fixup the register regions used by the cpufreq node on SM8350 SoC to
>> > support per core L3 DCVS.
>> >
>> 
>> That sounds good, but why are you dropping the platform-specific
>> compatible?
>> 
> 
> I also stared at this and the patch that changes the code for a while.
> 
> My understanding is that removing the platform-specific compatible is 
> part
> of not breaking 'old' DTBs. Old DTBs for SM8350 contain the larger 
> register
> regions and must be paired with 'epss_sm8250_soc_data' (driver code) 
> which
> has the 'old' 'reg_perf_state' offset. New SM8350 DTs only have the
> 'qcom,cpufreq-epss' compatible, which pairs their smaller register 
> regions
> with 'epss_soc_data' with the new 'reg_perf_state' offset.
> 
> It is super-confusing that the platform-specific compatible string is
> missing. The binding should probably mention that the two
> platform-specific compatible strings are for backwards compatibility
> only and should not be added to new or existing DT files that don't
> have them already. Maybe a 'qcom,sm8350-cpufreq-epss-v2' or similar
> should be added to avoid/reduce possible confusion and have to option
> to add SM8350 specific code later.

Bjorn,

https://patchwork.kernel.org/project/linux-arm-msm/cover/1629458622-4915-1-git-send-email-okukatla@codeaurora.org/

This series affects the design of the l3
provider support for sc7280 which will be
in a position to land in ~1-2 respins. So,
please share an early ACK or NACK regarding
the register re-ordering series so that we
can plan to get alternate acceptable versions
out faster on the list.


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