On 16/12/15 09:47, Ulf Hansson wrote: > On 16 December 2015 at 10:40, Jon Hunter <jonathanh@xxxxxxxxxx> wrote: >> Hi Ulf, >> >> On 15/12/15 19:54, Ulf Hansson wrote: >>> On 4 December 2015 at 15:57, Jon Hunter <jonathanh@xxxxxxxxxx> wrote: >>>> Enable PM_GENERIC_DOMAINS for tegra 64-bit devices. To ensure that devices >>>> dependent upon a particular power-domain are only probed when that power >>>> domain has been powered up, requires that PM is made mandatory for tegra >>>> 64-bit devices and so select this option for tegra as well. >>>> >>>> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx> >>>> --- >>>> arch/arm64/Kconfig.platforms | 2 ++ >>>> 1 file changed, 2 insertions(+) >>>> >>>> diff --git a/arch/arm64/Kconfig.platforms b/arch/arm64/Kconfig.platforms >>>> index 9806324fa215..e0b5bd0aff0f 100644 >>>> --- a/arch/arm64/Kconfig.platforms >>>> +++ b/arch/arm64/Kconfig.platforms >>>> @@ -93,6 +93,8 @@ config ARCH_TEGRA >>>> select GENERIC_CLOCKEVENTS >>>> select HAVE_CLK >>>> select PINCTRL >>>> + select PM >>>> + select PM_GENERIC_DOMAINS >>> >>> If you still want to allow ARCH_TEGRA to run without PM, you should >>> probably change to: >>> >>> select PM_GENERIC_DOMAINS if PM >> >> Per the changelog this is deliberate. If we allow !PM, then there is a >> potential that you could probe a device when the power domain is not >> powered on. I understand that some SoCs turn on all the power-domains >> when !PM but this will not work for tegra because we don't register the >> power domain until later in the boot and so we are relying upon probe >> deferral to defer the probe of devices that use power-domains. > > So what you are saying is that adding the PM domain support, will fix > some devices to become successfully probed as they were broken before? Not exactly. There is a legacy tegra_powergate_sequence_power_up() that has been used to date to get around this. However, by migrating to GENPD we really need to make PM mandatory, otherwise you could attempt to probe a device in a power domain that is not powered. In other words, you are probing blindly. I know some SoCs do this, but that does not seem very robust. Cheers Jon -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
