Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758277AbaFSQCs (ORCPT ); Thu, 19 Jun 2014 12:02:48 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:61000 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757376AbaFSQCp (ORCPT ); Thu, 19 Jun 2014 12:02:45 -0400 Message-ID: <53A309A5.9040204@linaro.org> Date: Thu, 19 Jun 2014 18:02:45 +0200 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Doug Anderson CC: Amit Daniel Kachhap , linux-samsung-soc , Kukjin Kim , Thomas Gleixner , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , David Riley , Tomasz Figa Subject: Re: [PATCH] clocksource: exynos-mct: Register the timer for stable udelay References: <1403091060-5054-1-git-send-email-amit.daniel@samsung.com> <53A2A86E.4090903@linaro.org> In-Reply-To: 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 On 06/19/2014 05:49 PM, Doug Anderson wrote: > Daniel, > > On Thu, Jun 19, 2014 at 2:07 AM, Daniel Lezcano > wrote: >> On 06/19/2014 01:17 AM, Doug Anderson wrote: >>> >>> Amit, >>> >>> Thanks for posting! >>> >>> On Wed, Jun 18, 2014 at 4:31 AM, Amit Daniel Kachhap >>> wrote: >>>> >>>> This patch register the exynos mct clocksource as the current timer >>>> as it has constant clock rate. This will generate correct udelay for the >>>> exynos platform and avoid using unnecessary calibrated jiffies. This >>>> change >>>> have been tested on exynos5420 based board. >>>> >>>> Signed-off-by: Amit Daniel Kachhap >>>> --- >>>> >>>> Patches from David Riley confirmed that udelay is broken in exynos5420. >>>> Link to those patches are, >>>> 1) https://patchwork.kernel.org/patch/4344911/ >>>> 2) https://patchwork.kernel.org/patch/4344881/ >>>> >>>> drivers/clocksource/exynos_mct.c | 11 +++++++++++ >>>> 1 file changed, 11 insertions(+) >>>> >>>> diff --git a/drivers/clocksource/exynos_mct.c >>>> b/drivers/clocksource/exynos_mct.c >>>> index 8d64200..57cb3dc 100644 >>>> --- a/drivers/clocksource/exynos_mct.c >>>> +++ b/drivers/clocksource/exynos_mct.c >>>> @@ -198,10 +198,21 @@ static u64 notrace exynos4_read_sched_clock(void) >>>> return exynos4_frc_read(&mct_frc); >>>> } >>>> >>>> +static struct delay_timer exynos4_delay_timer; >>>> + >>>> +static unsigned long exynos4_read_current_timer(void) >>>> +{ >>>> + return exynos4_frc_read(&mct_frc); >>> >>> >>> This is terribly inefficient to read all 64-bits and then cast back to >>> a 32-bit value. Replace with: >>> >>> return __raw_readl(reg_base + EXYNOS4_MCT_G_CNT_L); >>> >>> >>>> +} >>>> + >>>> static void __init exynos4_clocksource_init(void) >>>> { >>>> exynos4_mct_frc_start(0, 0); >>> >>> >>> Please rebase atop (1d80415 clocksource: exynos_mct: Don't reset the >>> counter during boot and resume), which is in linuxnext among other >>> places. >>> >>>> >>>> + exynos4_delay_timer.read_current_timer = >>>> &exynos4_read_current_timer; >>>> + exynos4_delay_timer.freq = clk_rate; >>>> + register_current_timer_delay(&exynos4_delay_timer); >>>> + >>>> if (clocksource_register_hz(&mct_frc, clk_rate)) >>>> panic("%s: can't register clocksource\n", mct_frc.name); >>> >>> >>> It does seem to work for me though. :) >> >> >> Doug, >> >> aren't you working on a 32 bits version ? So this patch could be simplified > > I could do that if someone told me that they'll land it. > > My understanding of the current status is: > * I posed the 64-bit version that's almost as fast as the 32-bit version. > * I asked if people want the 32-bit version: no answer > * I asked if anyone is opposed to the 64-bit version: no answer Yeah, that happens. I thought you were working on the 32 bits. > I know that you wanted me to clean up the description of the 64-bit > version so I was going to do that and repost. If there's someone > willing to review / ack the 32-bit version I'd be happy to do that > instead. Possibly I'll do both and a maintainer can choose which to > apply? Please, resend me the patch 1/3 as it is urgent with the changelog changed. > In the case here I was suggesting using the 32-bit version just > because on ARM32 there's totally no reason to read 64-bits. I hadn't > given a thought to ARM64. More on that in response to the other > messages. Is there a 64bits platform using exynos_mct ? -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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/