Re: [PATCH V3 0/5] iommu/arm-smmu: Add runtime pm/sleep support

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

On Thu, Mar 09, 2017 at 09:05:43PM +0530, Sricharan R wrote:
> This series provides the support for turning on the arm-smmu's
> clocks/power domains using runtime pm. This is done using the
> recently introduced device links patches, which lets the symmu's
> runtime to follow the master's runtime pm, so the smmu remains
> powered only when the masters use it.

Do you have any numbers for the power savings you achieve with this?
How often do we actually manage to stop the SMMU clocks on an SoC with
a handful of masters?

In other words, is this too coarse-grained to be useful, or is it common
that all the devices upstream of the SMMU are suspended?

Thanks,

Will

> 
> Took some reference from the exynos runtime patches [2].
> Tested this with MDP, GPU, VENUS devices on apq8096-db820c board.
> 
> Previous version of the patchset [1].
> 
> [V3]
>    * Reworked the patches to keep the clocks init/enabling function
>      seperately for each compatible.
> 
>    * Added clocks bindings for MMU40x/500.
> 
>    * Added a new compatible for qcom,smmu-v2 implementation and
>      the clock bindings for the same.
> 
>    * Rebased on top of 4.11-rc1
> 
> [V2]
>    * Split the patches little differently.
> 
>    * Addressed comments.
> 
>    * Removed the patch #4 [3] from previous post
>      for arm-smmu context save restore. Planning to
>      post this separately after reworking/addressing Robin's
>      feedback.
> 
>    * Reversed the sequence to disable clocks than enabling.
>      This was required for those cases where the
>      clocks are populated in a dependent order from DT.
> 
> [1] https://www.spinics.net/lists/linux-arm-msm/msg23870.html
> [2] https://lkml.org/lkml/2016/10/20/70
> [3] https://patchwork.kernel.org/patch/9389717/
> 
> Sricharan R (5):
>   iommu/arm-smmu: Add pm_runtime/sleep ops
>   iommu/arm-smmu: Add support for MMU40x/500 clocks
>   drivers: arm-smmu: Add clock support for QCOM_SMMUV2
>   iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device
>   iommu/arm-smmu: Add the device_link between masters and smmu
> 
>  .../devicetree/bindings/iommu/arm,smmu.txt         |  35 +++
>  drivers/iommu/arm-smmu.c                           | 349 ++++++++++++++++++++-
>  2 files changed, 373 insertions(+), 11 deletions(-)
> 
> -- 
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
> 
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