linux-kernel - Re: [RFC v3 00/10] DDR/L3 Scaling support on SDM845 and SC7180 SoCs

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Message-ID: <CAF6AEGuhKKbmK7xGX2RT=LbGz_r_4LsPOuU3-mj4gfhX3EBU-Q@mail.gmail.com>
Date:   Tue, 28 Jan 2020 18:54:20 -0800
From:   Rob Clark <robdclark@...il.com>
To:     Sibi Sankar <sibis@...eaurora.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Georgi Djakov <georgi.djakov@...aro.org>, saravanak@...gle.com,
        "Menon, Nishanth" <nm@...com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Rafael Wysocki <rjw@...ysocki.net>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Sharat Masetty <smasetty@...eaurora.org>
Subject: Re: [RFC v3 00/10] DDR/L3 Scaling support on SDM845 and SC7180 SoCs

On Mon, Jan 27, 2020 at 12:05 PM Sibi Sankar <sibis@...eaurora.org> wrote:
>
> This RFC series aims to extend cpu based scaling support to L3/DDR on
> SDM845 and SC7180 SoCs.
>
> Patches [1-3] - Blacklist SDM845 and SC7180 in cpufreq-dt-platdev
> Patches [5-7] - Hack in a way to add/remove multiple opp tables to
>                 a single device. I am yet to fix the debugfs to
>                 support multiple opp_tables per device but wanted to
>                 send what was working upstream to get an idea if multiple
>                 opp tables per device is a feature that will be useful
>                 upstream.
> Patches [9-10] - Add the cpu/cpu-ddr/cpu-l3 opp tables for SDM845
>                  and SC7180 SoCs.
>
> v3:
>  * Migrated to using Saravana's opp-kBps bindings [1]
>  * Fixed some misc comments from Rajendra
>  * Added support for SC7180
>
> v2:
>  * Incorporated Viresh's comments from:
>  https://lore.kernel.org/lkml/20190410102429.r6j6brm5kspmqxc3@vireshk-i7/
>  https://lore.kernel.org/lkml/20190410112516.gnh77jcwawvld6et@vireshk-i7/
>  * Dropped cpufreq-map passive governor
>
> Git-branch: https://github.com/QuinAsura/linux/tree/lnext-012420
>
> Some alternate ways of hosting the opp-tables:
> https://github.com/QuinAsura/linux/commit/50b92bfaadc8f9a0d1e12249646e018bd6d1a9d3
> https://github.com/QuinAsura/linux/commit/3d23d1eefd16ae6d9e3ef91e93e78749d8844e98
> Viresh didn't really like ^^ bindings and they dont really scale well. Just
> including them here for completeness.
>
> Depends on the following series:
> [1] https://patchwork.kernel.org/cover/11277199/
> [2] https://patchwork.kernel.org/cover/11055499/
> [3] https://patchwork.kernel.org/cover/11326381/

So drive-by question, from the perspective of someone who cares about
a non-cpu device that frequently enjoys a lot of bandwidth (ie. the
GPU).. any thoughts on how ddr scaling would/should work for workloads
where the CPU is not particularly busy?

BR,
-R

>
> Sibi Sankar (10):
>   arm64: dts: qcom: sdm845: Add SoC compatible to MTP
>   cpufreq: blacklist SDM845 in cpufreq-dt-platdev
>   cpufreq: blacklist SC7180 in cpufreq-dt-platdev
>   OPP: Add and export helper to update voltage
>   opp: of: export _opp_of_get_opp_desc_node
>   opp: Allow multiple opp_tables to be mapped to a single device
>   opp: Remove multiple attached opp tables from a device
>   cpufreq: qcom: Update the bandwidth levels on frequency change
>   arm64: dts: qcom: sdm845: Add cpu OPP tables
>   arm64: dts: qcom: sc7180: Add cpu OPP tables
>
>  arch/arm64/boot/dts/qcom/sc7180.dtsi    | 287 +++++++++++++++
>  arch/arm64/boot/dts/qcom/sdm845-mtp.dts |   2 +-
>  arch/arm64/boot/dts/qcom/sdm845.dtsi    | 453 ++++++++++++++++++++++++
>  drivers/cpufreq/cpufreq-dt-platdev.c    |   2 +
>  drivers/cpufreq/qcom-cpufreq-hw.c       | 246 +++++++++++--
>  drivers/opp/core.c                      | 111 +++++-
>  drivers/opp/of.c                        |   3 +-
>  drivers/opp/opp.h                       |   2 +
>  include/linux/pm_opp.h                  |  10 +
>  9 files changed, 1083 insertions(+), 33 deletions(-)
>
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project