From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Lei Subject: Re: [PATCH 1/3] ARM: OMAP2+: 32k-counter: Use hwmod lookup to check presence of 32k timer Date: Sat, 31 Mar 2012 09:30:31 +0800 Message-ID: References: <1326983304-14619-1-git-send-email-hvaibhav@ti.com> <1326983304-14619-2-git-send-email-hvaibhav@ti.com> <87mx9ej8fp.fsf@ti.com> <79CD15C6BA57404B839C016229A409A83181EF3F@DBDE01.ent.ti.com> <4F672364.3020403@ti.com> <79CD15C6BA57404B839C016229A409A83182386C@DBDE01.ent.ti.com> <79CD15C6BA57404B839C016229A409A83183EA54@DBDE01.ent.ti.com> <79CD15C6BA57404B839C016229A409A83183EB47@DBDE01.ent.ti.com> <79CD15C6BA57404B839C016229A409A831840C2E@DBDE01.ent.ti.com> <79CD15C6BA57404B839C016229A409A831840E0C@DBDE01.ent.ti.com> <4F7570FC.8000907@ti.com> <79CD15C6BA57404B839C016229A409A831840F82@DBDE01.ent.ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: "Shilimkar, Santosh" Cc: "Hilman, Kevin" , Paul Walmsley , "Cousson, Benoit" , "marc.zyngier@arm.com" , "johnstul@us.ibm.com" , "Hiremath, Vaibhav" , Tony Lindgren , "Balbi, Felipe" , "linux-omap@vger.kernel.org" , "DebBarma, Tarun Kanti" , "linux-arm-kernel@lists.infradead.org" List-Id: linux-omap@vger.kernel.org On Fri, Mar 30, 2012 at 5:20 PM, Shilimkar, Santosh > >> After Ming Lie's comment, the point that I came to my mind was, >> certainly there will be resolution difference between these two clocksou= rces, >> if =A0gptimer2 is sourced from sys_ck (26Mhz). >> > GPTIMER2 with sysclock is not an option. GPTIMER is not in wakeup domain > and when sysclock is cut, it stops. If neither CONFIG_PM or CONFIG_CPUIDLE is set, GPTIMER2 with sysclock should be an option. As I commented before, high resolution timer is very useful for trace, debu= g or high frequency perf sample. Suppose you want to trace the running time of one function, 32K counter can only give you a resolution of ~35us, which is too coarse to work well. Thanks, -- = Ming Lei From mboxrd@z Thu Jan 1 00:00:00 1970 From: tom.leiming@gmail.com (Ming Lei) Date: Sat, 31 Mar 2012 09:30:31 +0800 Subject: [PATCH 1/3] ARM: OMAP2+: 32k-counter: Use hwmod lookup to check presence of 32k timer In-Reply-To: References: <1326983304-14619-1-git-send-email-hvaibhav@ti.com> <1326983304-14619-2-git-send-email-hvaibhav@ti.com> <87mx9ej8fp.fsf@ti.com> <79CD15C6BA57404B839C016229A409A83181EF3F@DBDE01.ent.ti.com> <4F672364.3020403@ti.com> <79CD15C6BA57404B839C016229A409A83182386C@DBDE01.ent.ti.com> <79CD15C6BA57404B839C016229A409A83183EA54@DBDE01.ent.ti.com> <79CD15C6BA57404B839C016229A409A83183EB47@DBDE01.ent.ti.com> <79CD15C6BA57404B839C016229A409A831840C2E@DBDE01.ent.ti.com> <79CD15C6BA57404B839C016229A409A831840E0C@DBDE01.ent.ti.com> <4F7570FC.8000907@ti.com> <79CD15C6BA57404B839C016229A409A831840F82@DBDE01.ent.ti.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Mar 30, 2012 at 5:20 PM, Shilimkar, Santosh > >> After Ming Lie's comment, the point that I came to my mind was, >> certainly there will be resolution difference between these two clocksources, >> if ?gptimer2 is sourced from sys_ck (26Mhz). >> > GPTIMER2 with sysclock is not an option. GPTIMER is not in wakeup domain > and when sysclock is cut, it stops. If neither CONFIG_PM or CONFIG_CPUIDLE is set, GPTIMER2 with sysclock should be an option. As I commented before, high resolution timer is very useful for trace, debug or high frequency perf sample. Suppose you want to trace the running time of one function, 32K counter can only give you a resolution of ~35us, which is too coarse to work well. Thanks, -- Ming Lei