Messages in this thread | | | Subject | Re: [PATCH] iommu/arm-smmu: Add clk_bulk_{prepare/unprepare} to system pm callbacks | From | Robin Murphy <> | Date | Tue, 27 Jul 2021 11:33:04 +0100 |
| |
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...
Robin.
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> >> Co-developed-by: Rajendra Nayak <rnayak@codeaurora.org> >> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org> >> --- >> drivers/iommu/arm/arm-smmu/arm-smmu.c | 20 ++++++++++++++++++-- >> 1 file changed, 18 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c >> b/drivers/iommu/arm/arm-smmu/arm-smmu.c >> index d3c6f54110a5..9561ba4c5d39 100644 >> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c >> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c >> @@ -2277,6 +2277,13 @@ static int __maybe_unused >> arm_smmu_runtime_suspend(struct device *dev) >> static int __maybe_unused arm_smmu_pm_resume(struct device *dev) >> { >> + int ret; >> + struct arm_smmu_device *smmu = dev_get_drvdata(dev); >> + >> + ret = clk_bulk_prepare(smmu->num_clks, smmu->clks); >> + if (ret) >> + return ret; >> + >> if (pm_runtime_suspended(dev)) >> return 0; >> @@ -2285,10 +2292,19 @@ static int __maybe_unused >> arm_smmu_pm_resume(struct device *dev) >> static int __maybe_unused arm_smmu_pm_suspend(struct device *dev) >> { >> + int ret = 0; >> + struct arm_smmu_device *smmu = dev_get_drvdata(dev); >> + >> if (pm_runtime_suspended(dev)) >> - return 0; >> + goto clk_unprepare; >> - return arm_smmu_runtime_suspend(dev); >> + ret = arm_smmu_runtime_suspend(dev); >> + if (ret) >> + return ret; >> + >> +clk_unprepare: >> + clk_bulk_unprepare(smmu->num_clks, smmu->clks); >> + return ret; >> } >> static const struct dev_pm_ops arm_smmu_pm_ops = { >> > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu
| |