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

[Sibi Sankar]

Hey Lukasz,
Thanks for taking time to review
the series!

On 2020-01-29 15:16, Lukasz Luba wrote:
> Hi Sibi,
>
> In my opinion this solution depends on not always true assumption that
> CPUFreq notification chain will be triggered when there is a frequency

This series does not create any
devfreq devices nor use the cpufreq
notification chain. It just relies
on the opening up of required-opps
from being exclusive to gen-pd using
patches 1,2,3 from patch series[1].
With the fast path disabled and
schedutil enabled, this series will
not miss any cpufreq changes.

[1] https://patchwork.kernel.org/cover/11055499/

> switch. Extending devfreq governor (as in one of the dependent patch
> series that you have referred) by attaching to this notification
> chain makes sense only when the SchedUtil and fast_switch is not in 
> use.

fast_switch and cpu notifier chains
are mutually exclusive but schedutil
will still operate in the slow path
IIRC.

> The Schedutil CPUFreq governor might use the fast_switch from this
> driver and the notifications will not be triggered. I have also
> commented patch 08/10 which tries to disable it.
>
> Regards,
> Lukasz
>
> On 1/27/20 8:03 PM, Sibi Sankar 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/
> >
> > 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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