linux-kernel - Re: [PATCH v4 0/3] qcom-cpufreq-hw: Add CPU clock provider support

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Date:   Mon, 7 Nov 2022 15:40:37 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     andersson@...nel.org,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     krzysztof.kozlowski+dt@...aro.org, rafael@...nel.org,
        robh+dt@...nel.org, johan@...nel.org, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v4 0/3] qcom-cpufreq-hw: Add CPU clock provider support

On 02-11-22, 14:38, Manivannan Sadhasivam wrote:
> Hello,
> 
> This series adds clock provider support to the Qcom CPUFreq driver for
> supplying the clocks to the CPU cores in Qcom SoCs.
> 
> The Qualcomm platforms making use of CPUFreq HW Engine (EPSS/OSM) supply
> clocks to the CPU cores. But this is not represented clearly in devicetree.
> There is no clock coming out of the CPUFreq HW node to the CPU. This created
> an issue [1] with the OPP core when a recent enhancement series was submitted.
> Eventhough the issue got fixed in the OPP framework in the meantime, that's
> not a proper solution and this series aims to fix it properly.
> 
> There was also an attempt made by Viresh [2] to fix the issue by moving the
> clocks supplied to the CPUFreq HW node to the CPU. But that was not accepted
> since those clocks belong to the CPUFreq HW node only.
> 
> The proposal here is to add clock provider support to the Qcom CPUFreq HW
> driver to supply clocks to the CPUs that comes out of the EPSS/OSM block.
> This correctly reflects the hardware implementation.
> 
> The clock provider is a simple one that just provides the frequency of the
> clocks supplied to each frequency domain in the SoC using .recalc_rate()
> callback. The frequency supplied by the driver will be the actual frequency
> that comes out of the EPSS/OSM block after the DCVS operation. This frequency
> is not same as what the CPUFreq framework has set but it is the one that gets
> supplied to the CPUs after throttling by LMh.
> 
> This series has been tested on SM8450 based dev board with the OPP hack removed
> and hence there is a DTS change only for that platform. Once this series gets
> accepted, rest of the platform DTS can also be modified and finally the hack on
> the OPP core can be dropped.

Would be better to get an Ack from Bjorn before I apply these.

-- 
viresh