From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ulf Hansson Subject: Re: [PATCH V4 16/16] ARM64: tegra: select PM_GENERIC_DOMAINS Date: Wed, 16 Dec 2015 13:51:46 +0100 Message-ID: References: <1449241037-22193-1-git-send-email-jonathanh@nvidia.com> <1449241037-22193-17-git-send-email-jonathanh@nvidia.com> <567131A2.6030303@nvidia.com> <56714DA3.80707@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <56714DA3.80707@nvidia.com> Sender: linux-pm-owner@vger.kernel.org To: Jon Hunter Cc: Philipp Zabel , Stephen Warren , Thierry Reding , Alexandre Courbot , Rafael Wysocki , Kevin Hilman , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Vince Hsu , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" , "linux-pm@vger.kernel.org" List-Id: linux-tegra@vger.kernel.org On 16 December 2015 at 12:40, Jon Hunter wrote: > > On 16/12/15 09:47, Ulf Hansson wrote: >> On 16 December 2015 at 10:40, Jon Hunter wrote: >>> Hi Ulf, >>> >>> On 15/12/15 19:54, Ulf Hansson wrote: >>>> On 4 December 2015 at 15:57, Jon Hunter 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 >>>>> --- >>>>> 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. Thank for the clarification. I agree. You may add my: Reviewed-by: Ulf Hansson Kind regards Uffe