Messages in this thread | | | Subject | Re: [PATCH v8 3/5] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device | From | Robin Murphy <> | Date | Fri, 9 Mar 2018 17:36:31 +0000 |
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[ +Lorenzo ]
On 09/03/18 04:50, Tomasz Figa wrote: [...] >>> Now we need a way to do the check. Perhaps for the time being it would >>> be enough to just check for the power-domains property in DT? >> >> >> AFAICS, it might be as simple as arm_smmu_probe() doing this: >> >> /* >> * We want to avoid touching dev->power.lock in fastpaths unless >> * it's really going to do something useful - pm_runtime_enabled() >> * can serve as an ideal proxy for that decision. >> */ >> if (dev->pm_domain) >> pm_runtime_enable(dev); >> >> or maybe even just gate all the calls with "if (smmu->dev.pm_domain)" >> directly (like pcie-mediatek does), but I'm not sure which would be >> conceptually cleaner. > > Okay, that was easier than I expected. Thanks. :) > > Actually, there is one more thing that might need rechecking. Are you > sure that dev->pm_domain is NULL for the devices, for which we don't > want runtime PM to be enabled? I think ACPI was mentioned and ACPI > includes the concept of PM domains.
Thanks for pointing that out - thankfully, I've confirmed that the SMMUs on my Juno don't have dev->pm_domain set when booting with ACPI, and double-checking the ACPI code I think we're OK here. Since the SMMUs are only described in the static IORT table and not in the ACPI namespace, they won't have the ACPI companion device that acpi_dev_pm_attach() looks for, and thus should always be ignored. Lorenzo, do I have that right?
Robin.
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