From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: [RESEND PATCH v3] clocksource: exynos_mct: Add the support for Exynos 64bit SoC Date: Mon, 19 Jan 2015 10:27:50 +0100 Message-ID: <54BCCE16.8050607@linaro.org> References: <1421213603-5020-1-git-send-email-cw00.choi@samsung.com> <54B69072.4080607@kernel.org> <54B692FB.7030703@linaro.org> <54BC55BB.7050809@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <54BC55BB.7050809@samsung.com> Sender: linux-kernel-owner@vger.kernel.org To: Chanwoo Choi , Kukjin Kim Cc: tglx@linutronix.de, inki.dae@samsung.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, Kukjin Kim , Mark Rutland , Doug Anderson , 'Olof Johansson' , Thierry Reding , Paul Walmsley List-Id: linux-samsung-soc@vger.kernel.org On 01/19/2015 01:54 AM, Chanwoo Choi wrote: > Dear Daniel and Kukjin, > > On 01/15/2015 01:02 AM, Daniel Lezcano wrote: >> On 01/14/2015 04:51 PM, Kukjin Kim wrote: >>> On 01/14/15 14:33, Chanwoo Choi wrote: >>> >>> Hi, >>> >>> + Doug, Olof >>> >>>> This patch adds the support for Exynos 64bit SoC. The delay_timer = is only used >>>> for Exynos 32bit SoC. >>>> >>> Yes, the Exynos MCT(Multi-Core Timer) is 64bit timer and it is avai= lable >>> on 64bit exynos SoC such as exynos7. But basically ARMv8 architectu= re is >>> including ARM ARCH timer (ARM Generic Timer) and exynos7 also has >>> implemented it and additionally its access is faster than using mem= ory >>> mapped register called SFR for MCT...so Doug submitted patch to use= MCT >>> on 32bit exynos SoCs before. >>> >>> I know using MCT on 64bit exynos is usefulness for Power Management= and >>> I need to talk to relevant guys in office again. If anything, I'll = let >>> you know. >> >> I will wait for your answer before digging more the patch. Hi Chanwoo, [ ... ] > Do you have any comment about this patch? Yes, a similar patch has been posted for the tegra2 timer to run on=20 arm64. The patch in question put macros #ifdef CONFIG_ARM64 to disable=20 some parts of the code. That ended, the tegra2 timer was not needed for= =20 the moment because of the arch timer present, so it has been disabled=20 from the compilation until a proper fix without macros could be propose= d. It is happening exactly the same with this patch. As Kukjin pointed it,= =20 the exynos_mct may not be needed (at least until a backup timer is=20 needed at PM time). I suggest you look at a nicer way to fix that instead of introducing=20 macros (which is by the way valid but not recommended by the CodingStyl= e=20 rules) and perhaps sync with Paul and Thierry [cc'ed] to find a common=20 solution. -- Daniel --=20 Linaro.org =E2=94=82 Open source software fo= r ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog