Messages in this thread | | | Subject | Re: [PATCH v14 0/4] iommu/arm-smmu: Add runtime pm/sleep support | From | Robin Murphy <> | Date | Wed, 22 Aug 2018 16:43:32 +0100 |
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On 20/08/18 10:31, Tomasz Figa wrote: > Hi Robin, > > On Fri, Jul 27, 2018 at 4:02 PM Vivek Gautam > <vivek.gautam@codeaurora.org> wrote: >> >> This series provides the support for turning on the arm-smmu's >> clocks/power domains using runtime pm. This is done using >> device links between smmu and client devices. The device link >> framework keeps the two devices in correct order for power-cycling >> across runtime PM or across system-wide PM. >> >> With addition of a new device link flag DL_FLAG_AUTOREMOVE_SUPPLIER [8] >> (available in linux-next of Rafael's linux-pm tree [9]), the device links >> created between arm-smmu and its clients will be automatically purged >> when arm-smmu driver unbinds from its device. >> >> As not all implementations support clock/power gating, we are checking >> for a valid 'smmu->dev's pm_domain' to conditionally enable the runtime >> power management for such smmu implementations that can support it. >> Otherwise, the clocks are turned to be always on in .probe until .remove. >> With conditional runtime pm now, we avoid touching dev->power.lock >> in fastpaths for smmu implementations that don't need to do anything >> useful with pm_runtime. >> This lets us to use the much-argued pm_runtime_get_sync/put_sync() >> calls in map/unmap callbacks so that the clients do not have to >> worry about handling any of the arm-smmu's power. >> >> This series also adds support for Qcom's arm-smmu-v2 variant that >> has different clocks and power requirements. >> >> Previous version of this patch series is @ [2]. >> >> Tested this series on msm8996, and sdm845 after pulling in Rafael's linux-pm >> linux-next[9] and Joerg's iommu next[10] branches, and related changes for >> device tree, etc. >> >> Hi Robin, Will, >> I have addressed the comments for v13. If there's still a chance >> can you please consider pulling this for v4.19. >> Thanks. >> >> [v14] >> * Moved arm_smmu_device_reset() from arm_smmu_pm_resume() to >> arm_smmu_runtime_resume() so that the pm_resume callback calls >> only runtime_resume to resume the device. >> This should take care of restoring the state of smmu in systems >> in which smmu lose register state on power-domain collapse. > > It's been a while since this series was posted and no more comments > seem to be left anymore. Would you have some time to take a look > again? Thanks.
Other than the binding issue which turned up in the meantime, I *think* this is looking OK now in terms of being sufficiently safe for all the various awkward retention vs. state-loss combinations. There's almost certainly still ways to improve it in future, but what we have now seems like a reasonable starting point that isn't impossibly complicated to reason about.
Robin.
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