From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752145AbbJ3MhI (ORCPT ); Fri, 30 Oct 2015 08:37:08 -0400 Received: from mail-wi0-f170.google.com ([209.85.212.170]:32930 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750971AbbJ3MhF (ORCPT ); Fri, 30 Oct 2015 08:37:05 -0400 Subject: Re: [PATCH] clocksource: dw_apb_timer_of: support timer-based delay To: Jisheng Zhang References: <1446193659-1698-1-git-send-email-jszhang@marvell.com> <56334A1E.7060709@linaro.org> <20151030190929.4c46066c@xhacker> Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org From: Daniel Lezcano Message-ID: <5633646D.7030206@linaro.org> Date: Fri, 30 Oct 2015 13:37:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux i686; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151030190929.4c46066c@xhacker> 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 10/30/2015 12:09 PM, Jisheng Zhang wrote: > Dear Daniel, > > On Fri, 30 Oct 2015 11:44:46 +0100 > Daniel Lezcano wrote: > >> On 10/30/2015 09:27 AM, Jisheng Zhang wrote: >>> Implement an ARM delay timer to be used for udelay(). This allows us to >>> skip the delay loop calibration at boot on Marvell BG2, BG2Q, BG2CD >>> platforms. And after this patch, udelay() will be unaffected by CPU >>> frequency changes. >>> >>> Signed-off-by: Jisheng Zhang >>> --- >>> drivers/clocksource/Kconfig | 10 ++++++++++ >>> drivers/clocksource/dw_apb_timer_of.c | 16 ++++++++++++++++ >>> 2 files changed, 26 insertions(+) >>> >>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig >>> index a7726db..7b081805 100644 >>> --- a/drivers/clocksource/Kconfig >>> +++ b/drivers/clocksource/Kconfig >>> @@ -29,6 +29,16 @@ config DW_APB_TIMER_OF >>> select DW_APB_TIMER >>> select CLKSRC_OF >>> >>> +config DW_APB_TIMER_BASED_DELAY >>> + bool "DW APB timer based delay" >>> + depends on ARM && DW_APB_TIMER_OF >>> + default n >>> + help >>> + This option enables support for using the DW APB timer to >>> + implement timer-based delay. It is useful for skiping the >>> + delay loop calibration at boot on some platforms. And the >>> + udelay() will be unaffected by CPU frequency changes. >>> + >> >> Why do you want it to be optional ? >> > > Because in some platforms which has arm arch timer, this dw apb timer > delay isn't needed, the arch timer is better. So we want it be optional > so that the platforms which need this feature select it manually when config > the kernel. Correct me if I am wrong. If you have the arch timer, you don't need the dw apb timer at all, no ? So the selection would be arch arm timer *or* dw_apb_timer ? not arch_arm_timer for delay and dw_apb_timer for clockevents, right ? -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog