From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH] ARM: avoid Cortex-A9 livelock on tight dmb loops Date: Tue, 10 Apr 2018 16:28:27 +0100 Message-ID: <20180410152827.GE15514@arm.com> References: <20180410134149.GQ5700@atomide.com> <685f80e3-30b3-8806-b81c-8de456507001@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <685f80e3-30b3-8806-b81c-8de456507001@ti.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Tero Kristo Cc: Paul Walmsley , Rajendra Nayak , Tony Lindgren , Russell King , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-omap@vger.kernel.org On Tue, Apr 10, 2018 at 05:12:37PM +0300, Tero Kristo wrote: > On 10/04/18 16:41, Tony Lindgren wrote: > >* Russell King [180410 10:43]: > >>diff --git a/arch/arm/mach-omap2/prm_common.c b/arch/arm/mach-omap2/prm_common.c > >>index 021b5a8b9c0a..d4ddc78b2a0b 100644 > >>--- a/arch/arm/mach-omap2/prm_common.c > >>+++ b/arch/arm/mach-omap2/prm_common.c > >>@@ -523,7 +523,7 @@ void omap_prm_reset_system(void) > >> prm_ll_data->reset_system(); > >> while (1) > >>- cpu_relax(); > >>+ cpu_do_idle(); > >> } > > > >Hmm we need to check so the added WFI here does not cause an > >undesired change to a low power state. Adding Tero to Cc also. > > Generally it is a bad idea to call arbitrary WFI within OMAP architecture, > as this triggers a PRCM power transition and will most likely cause a hang > if not controlled properly. > > Has this patch been tested on any platform that supports proper power > management? An alternative to WFI would be a DSB, which should avoid unexpected interactions with power management. Will