[ +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?
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