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

From: Rob Clark <robdclark@gmail.com>
To: Sibi Sankar <sibis@codeaurora.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>,
	Stephen Boyd <sboyd@kernel.org>,
	Georgi Djakov <georgi.djakov@linaro.org>,
	saravanak@google.com, "Menon, Nishanth" <nm@ti.com>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Andy Gross <agross@kernel.org>,
	David Brown <david.brown@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Rafael Wysocki <rjw@rjwysocki.net>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Douglas Anderson <dianders@chromium.org>,
	Matthias Kaehlcke <mka@chromium.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Amit Kucheria <amit.kucheria@linaro.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Jordan Crouse <jcrouse@codeaurora.org>,
	Sharat Masetty <smasetty@codeaurora.org>
Subject: Re: [RFC v3 00/10] DDR/L3 Scaling support on SDM845 and SC7180 SoCs
Date: Tue, 28 Jan 2020 18:54:20 -0800	[thread overview]
Message-ID: <CAF6AEGuhKKbmK7xGX2RT=LbGz_r_4LsPOuU3-mj4gfhX3EBU-Q@mail.gmail.com> (raw)
In-Reply-To: <20200127200350.24465-1-sibis@codeaurora.org>

On Mon, Jan 27, 2020 at 12:05 PM Sibi Sankar <sibis@codeaurora.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(-)
>
> --
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