linux-kernel - Re: [PATCH v12 0/4] Invoke rpmh

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Date:   Mon, 9 Mar 2020 13:57:51 +0530
From:   Maulik Shah <mkshah@...eaurora.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Evan Green <evgreen@...omium.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Lina Iyer <ilina@...eaurora.org>, lsrao@...eaurora.org
Subject: Re: [PATCH v12 0/4] Invoke rpmh_flush for non OSI targets


On 3/6/2020 3:52 AM, Doug Anderson wrote:
> Hi,
>
> On Thu, Mar 5, 2020 at 9:07 AM Maulik Shah <mkshah@...eaurora.org> wrote:
>> Changes in v12:
>> - Kconfig change to remove COMPILE_TEST was dropped in v11, reinclude it.
>>
>> Changes in v11:
>> - Address Doug's comments on change 2 and 3
>> - Include change to invalidate TCSes before flush from [4]
>>
>> Changes in v10:
>> - Address Evan's comments to update commit message on change 2
>> - Add Evan's Reviewed by on change 2
>> - Remove comment from rpmh_flush() related to last CPU invoking it
>> - Rebase all changes on top of next-20200302
>>
>> Changes in v9:
>> - Keep rpmh_flush() to invoke from within cache_lock
>> - Remove comments related to only last cpu invoking rpmh_flush()
>>
>> Changes in v8:
>> - Address Stephen's comments on changes 2 and 3
>> - Add Reviewed by from Stephen on change 1
>>
>> Changes in v7:
>> - Address Srinivas's comments to update commit text
>> - Add Reviewed by from Srinivas
>>
>> Changes in v6:
>> - Drop 1 & 2 changes from v5 as they already landed in maintainer tree
>> - Drop 3 & 4 changes from v5 as no user at present for power domain in rsc
>> - Rename subject to appropriate since power domain changes are dropped
>> - Rebase other changes on top of next-20200221
>>
>> Changes in v5:
>> - Add Rob's Acked by on dt-bindings change
>> - Drop firmware psci change
>> - Update cpuidle stats in dtsi to follow PC mode
>> - Include change to update dirty flag when data is updated from [4]
>> - Add change to invoke rpmh_flush when caches are dirty
>>
>> Changes in v4:
>> - Add change to allow hierarchical topology in PC mode
>> - Drop hierarchical domain idle states converter from v3
>> - Address Merge sc7180 dtsi change to add low power modes
>>
>> Changes in v3:
>> - Address Rob's comment on dt property value
>> - Address Stephen's comments on rpmh-rsc driver change
>> - Include sc7180 cpuidle low power mode changes from [1]
>> - Include hierarchical domain idle states converter change from [2]
>>
>> Changes in v2:
>> - Add Stephen's Reviewed-By to the first three patches
>> - Addressed Stephen's comments on fourth patch
>> - Include changes to connect rpmh domain to cpuidle and genpds
>>
>> Resource State Coordinator (RSC) is responsible for powering off/lowering
>> the requirements from CPU subsystem for the associated hardware like buses,
>> clocks, and regulators when all CPUs and cluster is powered down.
>>
>> RSC power domain uses last-man activities provided by genpd framework based
>> on Ulf Hansoon's patch series[3], when the cluster of CPUs enter deepest
>> idle states. As a part of domain poweroff, RSC can lower resource state
>> requirements by flushing the cached sleep and wake state votes for various
>> resources.
>>
>> [1] https://patchwork.kernel.org/patch/11218965
>> [2] https://patchwork.kernel.org/patch/10941671
>> [3] https://patchwork.kernel.org/project/linux-arm-msm/list/?series=222355
>> [4] https://patchwork.kernel.org/project/linux-arm-msm/list/?series=236503
>>
>> Maulik Shah (3):
>>   arm64: dts: qcom: sc7180: Add cpuidle low power states
>>   soc: qcom: rpmh: Update dirty flag only when data changes
>>   soc: qcom: rpmh: Invoke rpmh_flush for dirty caches
>>
>>  arch/arm64/boot/dts/qcom/sc7180.dtsi | 78 ++++++++++++++++++++++++++++++++++++
>>  drivers/soc/qcom/rpmh.c              | 27 ++++++++++---
>>  2 files changed, 100 insertions(+), 5 deletions(-)
> One overall optimization idea?
>
> Should we add two API calls:
>
> rpmh_start_operations()
> rpmh_end_operations()
>
> These optional API calls would be an optimization a client could use.
> When rpmh_start_operations() is called then RPMH code will inhibit
> flushing (but will still update the "dirty" flag).  When
> rpmh_end_operations() is called then the RPMH will flush if the dirty
> flag is set.
>
> This is a pretty simple concept but should have a huge impact in the
> number of times we program hardware in non-OSI mode.  Specifically, if
> we don't do that and we look at what happens in the interconnect code:
>
> 1. We "invalidate" the batch.  We have to flush the non-batch commands
> back into the hardware.
>
> 2. We program the "wake only" commands.  We have to flush the batch
> wake-only commands and also the non-batch commands back into the
> hardware.
>
> 3. We program the "sleep only" commands.  We have to flush yet again
> with everything.
>
>
>
> -Doug

Implemented in v13.

Thanks,
Maulik

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