From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH] save and restore etm state across core OFF modes Date: Tue, 12 Jan 2010 14:15:10 -0800 Message-ID: <20100112221510.GC2986@atomide.com> References: <1263315891-4440-1-git-send-email-virtuoso@slind.org> <4B4CADA9.4020502@ti.com> <20100112173022.GG29059@shisha.kicks-ass.net> <4B4CB259.2010301@ti.com> <20100112210404.GB2986@atomide.com> <20100112214654.GH29059@shisha.kicks-ass.net> <4B4CF2D7.9000200@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mho-02-ewr.mailhop.org ([204.13.248.72]:57045 "EHLO mho-02-ewr.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751320Ab0ALWPJ (ORCPT ); Tue, 12 Jan 2010 17:15:09 -0500 Content-Disposition: inline In-Reply-To: <4B4CF2D7.9000200@ti.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Nishanth Menon Cc: Kevin Hilman , "linux-omap@vger.kernel.org" , "Woodruff, Richard" * Nishanth Menon [100112 14:06]: > Alexander Shishkin had written, on 01/12/2010 03:46 PM, the following: > >On Tue, Jan 12, 2010 at 01:04:04 -0800, Tony Lindgren wrote: > >>* Nishanth Menon [100112 09:31]: > >>>Alexander Shishkin had written, on 01/12/2010 11:30 AM, the following: > >>>>On Tue, Jan 12, 2010 at 11:13:13 -0600, Nishanth Menon wrote: > >>>>>Alexander Shishkin had written, on 01/12/2010 11:04 AM, the following: > >>>>>>diff --git a/arch/arm/mach-omap2/sleep34xx.S b/arch/arm/mach-omap2/sleep34xx.S > >>>>>>index 69521be..0a5ec86 100644 > >>>>>>--- a/arch/arm/mach-omap2/sleep34xx.S > >>>>>>+++ b/arch/arm/mach-omap2/sleep34xx.S > >>>[...] > >>>>>> /* Store current cpsr*/ > >>>>>> mrs r2, cpsr > >>>>>> stmia r8!, {r2} > >>>>>>@@ -520,6 +616,7 @@ clean_caches: > >>>>>> cmp r9, #1 /* Check whether L2 inval is required or not*/ > >>>>>> bne skip_l2_inval > >>>>>>clean_l2: > >>>>>>+#if 0 > >>>>>my aversion to #if 0 kicks in here :(.. do we have an alternative > >>>>>like using the CONFIG_ENABLE_OFF_MODE_JTAG_ETM_DEBUG or something > >>>>>else? > >>>>Fair enough. I could replace it with "#if !defined(...)" as the first > >>>>thing that comes to mind. This way it will only take disabling the > >>>>config option to catch any possible regressions in between. Does this > >>>>sound reasonable? > >>>sounds ok to me.. unless folks have ideas coz of clean_l2 label.. > >>>more comments might be useful before a rev2 of the patch.. > >>The best solution would be to be able to toggle this via sysfs or > >>debugfs by swapping the sram code for idle loop when JTAG support > >>is needed. > > > >Well, if you say, compile the ETM driver in, this will be needed most of > >the time. > > > I can think of reasons for an against a sysfs entry (as part of > discussion -warning lot of self contradictions below- but I think > might save a bit of back and froth ;)): > > for sysfs entry: > a) save and restore will have additional latency when you save a > chunk such as EMU domain regs - this will not be needed in > production phones, disabling it might pop up surprises There's no overhead if you're just replacing the function loaded to SRAM as needed. But for sure it's a debug tool only. Regards, Tony