Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932472AbbLPLlK (ORCPT ); Wed, 16 Dec 2015 06:41:10 -0500 Received: from hqemgate15.nvidia.com ([216.228.121.64]:1313 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752063AbbLPLlG (ORCPT ); Wed, 16 Dec 2015 06:41:06 -0500 X-PGP-Universal: processed; by hqnvupgp08.nvidia.com on Wed, 16 Dec 2015 03:37:35 -0800 Subject: Re: [PATCH V4 16/16] ARM64: tegra: select PM_GENERIC_DOMAINS To: Ulf Hansson References: <1449241037-22193-1-git-send-email-jonathanh@nvidia.com> <1449241037-22193-17-git-send-email-jonathanh@nvidia.com> <567131A2.6030303@nvidia.com> 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" From: Jon Hunter Message-ID: <56714DA3.80707@nvidia.com> Date: Wed, 16 Dec 2015 11:40:19 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.21.132.159] X-ClientProxiedBy: UKMAIL101.nvidia.com (10.26.138.13) To UKMAIL101.nvidia.com (10.26.138.13) Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2450 Lines: 57 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. Cheers Jon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/