From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755776AbbJ3Mmj (ORCPT ); Fri, 30 Oct 2015 08:42:39 -0400 Received: from mout.kundenserver.de ([212.227.17.24]:57956 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754786AbbJ3Mmh (ORCPT ); Fri, 30 Oct 2015 08:42:37 -0400 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: Jisheng Zhang , Daniel Lezcano , tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] clocksource: dw_apb_timer_of: support timer-based delay Date: Fri, 30 Oct 2015 13:42:01 +0100 Message-ID: <3950525.pKSJGoymu4@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20151030190929.4c46066c@xhacker> References: <1446193659-1698-1-git-send-email-jszhang@marvell.com> <56334A1E.7060709@linaro.org> <20151030190929.4c46066c@xhacker> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:TwmB4G1ncLovjPmHBWQPYLod9L6/+UcEHXrwHLGGJjwQ6pw+AYd RT9Jt0A/xzmbG7N/JRkZ5Tol8mPjisa06wLE+QE+GPCf+/M2Eidhs/lf0PehIKWCZNjRKnJ xtYgbR1kT6o9CwpTkKk3eNzEZ3Gc01lDNrfHQUHGys48UcIxZqv4vRPln6FjjM+EKbYcoJC TTxJ4EUdAl55gLeIbJUYA== X-UI-Out-Filterresults: notjunk:1;V01:K0:NJrFDIh9mCw=:iXzt5gk9mRjkwzxyuSD04G hXMbtcESJcS3TSG9yJPjJMsBL3mTDCNtbs/ahmVNd6xr8ld89XULhXUxK+utWhO5eFZMYuODq gdFt17hrxw8ufll1e1LKPSthXt8kT9Zt9DyNb91RqKoeeiolYKpwcv5/gJS33NnBqW/lSa/Hc ++fNJGQMqYYucu83a9w6H8kfGo90mCw6WeZ5MWjHTOVOhxjtWoPLf3ICToy78+UXWUbIZiRBz KpLaKI2Xl0nlei6vXk1Y/k/Kb8Vo/xW0V4hdlz83kAiuTjh0agT+6EVssz5xRMKqjH6hg84Wj Hi3Kq7kmrV9ZVWYD8Ae8bWtPlpJ4811cg/t9WD1FG4CtFJQyA3/BO7dfzFRwh9lA8TUl/965L wPSTyAZDHxtuqt1/lfuEiUB2DHXx8Ov0GYFE9JF9FQtgVndfCFULvXKkbImuT9XO2iFN9lhEb 1MKcYnd5mBhSlGvO+5akwOFi45r1FOYru2pyWXOL7pl3P+WoadAXtqSjtDydG3jHrlIpCfz0P 9GVgQhylLj1XnUEnaUT3tkqMa5XY6z8ag6IQjSguFS+iHKnKbHFitKmPztiZLXmriY1TECpmR au2xCFjk/6wcKjG58HCV4kaRoy7nTlGQwxJLsPAAr3l+4vsGQ2fhqv9RKk7WiZr8Ew/bdaPoA /SDkQrWFipNJcmVqqYZAabv/XJvkwPvxPC/QPGC+Yz0oodi3r1/sYbc0z5VenhPGAcdna572z cSZbMZ/vOkUp/gB1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 30 October 2015 19:09:29 Jisheng Zhang wrote: > > > 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. > This is not ideal from an overall maintenance perspective. We want to be able to have a kernel with all drivers enabled that gives us the best behavior on all platforms. The current behavior appears to be that we override all previous registrations as long as the new one is higher resolution. Is that the case here? I.e. does the arch timer have a lower resultion than the dw-apb timer but have some other advantages? Arnd