Messages in this thread | | | Date | Tue, 27 Jul 2021 16:05:12 +0530 | From | Sai Prakash Ranjan <> | Subject | Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks |
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Hi Robin,
On 2021-07-27 16:03, Robin Murphy wrote: > On 2021-07-27 11:25, Robin Murphy wrote: >> On 2021-07-27 10:33, Sai Prakash Ranjan wrote: >>> Some clocks for SMMU can have parent as XO such as >>> gpu_cc_hub_cx_int_clk >>> of GPU SMMU in QTI SC7280 SoC and in order to enter deep sleep states >>> in >>> such cases, we would need to drop the XO clock vote in unprepare call >>> and >>> this unprepare callback for XO is in RPMh (Resource Power >>> Manager-Hardened) >>> clock driver which controls RPMh managed clock resources for new QTI >>> SoCs >>> and is a blocking call. >>> >>> Given we cannot have a sleeping calls such as clk_bulk_prepare() and >>> clk_bulk_unprepare() in arm-smmu runtime pm callbacks since the iommu >>> operations like map and unmap can be in atomic context and are in >>> fast >>> path, add this prepare and unprepare call to drop the XO vote only >>> for >>> system pm callbacks since it is not a fast path and we expect the >>> system >>> to enter deep sleep states with system pm as opposed to runtime pm. >>> >>> This is a similar sequence of clock requests (prepare,enable and >>> disable,unprepare) in arm-smmu probe and remove. >> >> Nope. We call arm_smmu_rpm_get(), which may resume the device, from >> atomic contexts. clk_prepare() may sleep. This doesn't work. > > Urgh, or maybe I skimmed the commit message too lightly *and* managed > to totally misread the patch, sorry :( > > I'll wake up some more and try again later... >
No worries, we took our time looking through that many times before posting this :)
Thanks, Sai
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