linux-kernel - Re: [PATCH v2 3/3] cpufreq: qcom-nvmem: Add MSM8909

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Date:   Wed, 18 Oct 2023 10:42:31 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Stephan Gerhold <stephan.gerhold@...nkonzept.com>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Ilia Lin <ilia.lin@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>,
        Stephan Gerhold <stephan@...hold.net>
Subject: Re: [PATCH v2 3/3] cpufreq: qcom-nvmem: Add MSM8909



On 10/18/23 10:06, Stephan Gerhold wrote:
> When the MSM8909 SoC is used together with the PM8909 PMIC the primary
> power supply for the CPU (VDD_APC) is shared with other components to
> the SoC, namely the VDD_CX power domain typically supplied by the PM8909
> S1 regulator. This means that all votes for necessary performance states
> go via the RPM firmware which collects the requirements from all the
> processors in the SoC. The RPM firmware then chooses the actual voltage
> based on the performance states ("corners"), depending on calibration
> values in the NVMEM and other factors.
> 
> The MSM8909 SoC is also sometimes used with the PM8916 or PM660 PMIC.
> In that case there is a dedicated regulator connected to VDD_APC and
> Linux is responsible to do adaptive voltage scaling using CPR (similar
> to the existing code for QCS404).
> 
> This difference can be described in the device tree, by either assigning
> the CPU a power domain from RPMPD or from the CPR driver.
> 
> Describe this using "perf" as generic power domain name, which is also
> used already for SCMI based platforms.
> 
> Also add a simple function that reads the speedbin from a NVMEM cell
> and sets it as-is for opp-supported-hw. The actual bit position can be
> described in the device tree without additional driver changes.
> 
> Signed-off-by: Stephan Gerhold <stephan.gerhold@...nkonzept.com>
> ---
Acked-by: Konrad Dybcio <konrad.dybcio@...aro.org>

Konrad