Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753195AbcD0KP5 (ORCPT ); Wed, 27 Apr 2016 06:15:57 -0400 Received: from foss.arm.com ([217.140.101.70]:33465 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752177AbcD0KPz (ORCPT ); Wed, 27 Apr 2016 06:15:55 -0400 Subject: Re: [PATCH v1] ARM: clocksource: make ARM_GLOBAL_TIMER selectable To: Grygorii Strashko , Liviu Dudau References: <1461684532-16848-1-git-send-email-grygorii.strashko@ti.com> <20160426160245.GI28464@e106497-lin.cambridge.arm.com> <571FC2EC.9090605@ti.com> Cc: kernel@stlinux.com, Tony Lindgren , Sekhar Nori , Masahiro Yamada , Wei Xu , Jesper Nilsson , Florian Fainelli , Russell King , Daniel Lezcano , Michal Simek , linux-arm-kernel@axis.com, linux-rockchip@lists.infradead.org, bcm-kernel-feedback-list@broadcom.com, Arnd Bergmann , Mike Looijmans , Lars Persson , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Maxime Coquelin , Srinivas Kandagatla , linux-kernel@vger.kernel.org, Sascha Hauer , Sudeep Holla , Olof Johansson , Jun Nie , Shawn Guo From: Robin Murphy Message-ID: <57209154.6050508@arm.com> Date: Wed, 27 Apr 2016 11:15:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <571FC2EC.9090605@ti.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4860 Lines: 122 On 26/04/16 20:35, Grygorii Strashko wrote: > On 04/26/2016 07:02 PM, Liviu Dudau wrote: >> On Tue, Apr 26, 2016 at 06:28:52PM +0300, Grygorii Strashko wrote: >> >> Hi Grygorii, >> >> First time I'm seeing this patch, so I have a few questions, mostly >> related to the commit message: > > Hm. You are in cc for RFC. > Sry, forgot to add link [1]. > >> >>> This patch intended to fix following cases: >>> - SoC-A has ARM GT, defines DT node for ARM GT and selects >>> ARM_GLOBAL_TIMER statically in Kconfig file. SoC-B has ARM GT and >>> defines DT node for ARM GT, but do not selects ARM_GLOBAL_TIMER >>> statically in Kconfig file. In case of multiplatform build ARM GT will >>> be implicitly enabled for SoC-B. >> >> Well, SoC-B has the GT *and* the DT node, so what is the problem with >> enabling it for SoC-B? If there are reasons not to use the Global Timer >> on SoC-B, surely a better option would be to mark it in DT with status = "disabled"; > > This was rejected [2]. DT describes HW and if it is functional the status = "disabled" > is not good choice. > ARM GT can't be used as clocksource/sched_clock/clockevent when CPUFreq or > CPUIdle are enabled :(, and this is Linux specific functionality and > not HW description. It sounds to me like the cleanest option might then be to address it within the Linux-specific driver itself. How feasible would it be for the GT driver to detect at runtime whether CPUfreq/idle will be used and simply refuse to register as a clocksource if so? (I guess there are probably horrible initialisation order issues, at least...) Robin. >> >>> >>> - There is no way to disable ARM GT without modifying Kconfig file, >>> once ARM_GLOBAL_TIMER is selected statically in Kconfig file. >> >> What about disabling the DT node? >> >> Not sure I properly understand the problem you are trying to solve here. > > I'd like to have way to enable/disable ARM GT without modifying Kernel sources > (Kconfig specifically) which is now impossible. > >> >>> >>> Hence, fix above case by defining both HAVE_ARM_GLOBAL_TIMER and >>> ARM_GLOBAL_TIMER as recommended by 'Adding common features and make >>> the usage configurable' section in kconfig-language.txt. All places in >>> ARM folder where ARM_GLOBAL_TIMER was used now replaced on >>> HAVE_ARM_GLOBAL_TIMER. >> >> I'm OK with the way you have changed ARM_GLOBAL_TIMER from a sticky config >> option to a selectable one, but I would like more details on the problem >> this was causing you. >> > > The same HW (board) could be used with PM features enabled (power saving) > and disabled (-RT). Without this change it will require to have > and maintain two branches, but with it - just separate defconfig. > > [1] http://lists.infradead.org/pipermail/linux-rockchip/2016-February/007159.html > [2] http://www.spinics.net/lists/devicetree/msg102918.html > >> >>> >>> Cc: Daniel Lezcano >>> Cc: Florian Fainelli >>> Cc: Russell King >>> Cc: Wei Xu >>> Cc: Shawn Guo >>> Cc: Sascha Hauer >>> Cc: Srinivas Kandagatla >>> Cc: Maxime Coquelin >>> Cc: Masahiro Yamada >>> Cc: Liviu Dudau >>> Cc: Sudeep Holla >>> Cc: Jun Nie >>> Cc: Michal Simek >>> Cc: Jesper Nilsson >>> Cc: Lars Persson >>> Cc: Mike Looijmans >>> Acked-by: Sören Brinkmann >>> Acked-by: Moritz Fischer >>> Signed-off-by: Grygorii Strashko >>> --- >>> Changes is v1: >>> - updated mach-artpec >>> - rebased on top of tip: timers/core >>> commit: 86d3473 time: Introduce do_sys_settimeofday64() >>> >>> arch/arm/mach-artpec/Kconfig | 2 +- >>> arch/arm/mach-bcm/Kconfig | 4 ++-- >>> arch/arm/mach-hisi/Kconfig | 2 +- >>> arch/arm/mach-imx/Kconfig | 2 +- >>> arch/arm/mach-rockchip/Kconfig | 2 +- >>> arch/arm/mach-sti/Kconfig | 2 +- >>> arch/arm/mach-uniphier/Kconfig | 2 +- >>> arch/arm/mach-vexpress/Kconfig | 2 +- >>> arch/arm/mach-zx/Kconfig | 2 +- >>> arch/arm/mach-zynq/Kconfig | 2 +- >>> drivers/clocksource/Kconfig | 7 ++++++- >>> 11 files changed, 17 insertions(+), 12 deletions(-) >>> >>> diff --git a/arch/arm/mach-artpec/Kconfig b/arch/arm/mach-artpec/Kconfig >>> index 6cbe5a2..6cbca77 100644 >>> --- a/arch/arm/mach-artpec/Kconfig >>> +++ b/arch/arm/mach-artpec/Kconfig >>> @@ -9,7 +9,7 @@ config MACH_ARTPEC6 >>> depends on ARCH_MULTI_V7 >>> select ARM_AMBA >>> select ARM_GIC >>> - select ARM_GLOBAL_TIMER > > [...] >