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Date:   Thu, 20 Jul 2023 09:44:38 -0700
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Subject: Re: [PATCH v2 00/15] UFS: Add OPP and interconnect support
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To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        vireshk@kernel.org, nm@ti.com, sboyd@kernel.org,
        myungjoo.ham@samsung.com, kyungmin.park@samsung.com,
        cw00.choi@samsung.com, andersson@kernel.org,
        konrad.dybcio@linaro.org, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
        jejb@linux.ibm.com, martin.petersen@oracle.com
Cc:     alim.akhtar@samsung.com, avri.altman@wdc.com,
        linux-scsi@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
        quic_asutoshd@quicinc.com, quic_cang@quicinc.com,
        quic_nitirawa@quicinc.com, quic_narepall@quicinc.com,
        quic_bhaskarv@quicinc.com, quic_richardp@quicinc.com,
        quic_nguyenb@quicinc.com, quic_ziqichen@quicinc.com,
        bmasney@redhat.com, krzysztof.kozlowski@linaro.org,
        linux-kernel@vger.kernel.org
References: <20230720054100.9940-1-manivannan.sadhasivam@linaro.org>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <20230720054100.9940-1-manivannan.sadhasivam@linaro.org>
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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.