linux-kernel - Re: [PATCH v2 00/15] UFS: Add OPP and interconnect support

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Message-ID: <e46f077f-4602-1882-bc14-e8df2a216773@acm.org>
Date:   Thu, 20 Jul 2023 09:44:38 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        vireshk@...nel.org, nm@...com, sboyd@...nel.org,
        myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
        cw00.choi@...sung.com, andersson@...nel.org,
        konrad.dybcio@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        jejb@...ux.ibm.com, martin.petersen@...cle.com
Cc:     alim.akhtar@...sung.com, avri.altman@....com,
        linux-scsi@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        quic_asutoshd@...cinc.com, quic_cang@...cinc.com,
        quic_nitirawa@...cinc.com, quic_narepall@...cinc.com,
        quic_bhaskarv@...cinc.com, quic_richardp@...cinc.com,
        quic_nguyenb@...cinc.com, quic_ziqichen@...cinc.com,
        bmasney@...hat.com, krzysztof.kozlowski@...aro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 00/15] UFS: Add OPP and interconnect support

On 7/19/23 22:40, Manivannan Sadhasivam wrote:
> This series adds OPP (Operating Points) support to UFSHCD driver and
> interconnect support to Qcom UFS driver.
> 
> Motivation behind adding OPP support is to scale both clocks as well as
> regulators/performance state dynamically. Currently, UFSHCD just scales
> clock frequency during runtime with the help of "freq-table-hz" property
> defined in devicetree. With the addition of OPP tables in devicetree (as
> done for Qcom SDM845 and SM8250 SoCs in this series) UFSHCD can now scale
> both clocks and performance state of power domain which helps in power
> saving.
> 
> For the addition of OPP support to UFSHCD, there are changes required to
> the OPP framework and devfreq drivers which are also added in this series.
> 
> Finally, interconnect support is added to Qcom UFS driver for scaling the
> interconnect path dynamically. This is required to avoid boot crash in
> recent SoCs and also to save power during runtime. More information is
> available in patch 13/13.

How much power can OPP save? I'm asking this since I'm wondering whether
the power saved by OPP outweighs the complexity added by this patch series.

Thanks,

Bart.