From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH] ARM: OMAP4: Workaround the OCP synchronisation issue with 32K synctimer. Date: Tue, 13 Mar 2012 09:31:46 -0700 Message-ID: <87vcm8tqbx.fsf@ti.com> References: <1331566388-2397-1-git-send-email-santosh.shilimkar@ti.com> <87399d225f.fsf@ti.com> <4F5F098E.4040006@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from na3sys009aog119.obsmtp.com ([74.125.149.246]:34157 "EHLO na3sys009aog119.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751662Ab2CMQbv (ORCPT ); Tue, 13 Mar 2012 12:31:51 -0400 Received: by iagz16 with SMTP id z16so1483013iag.33 for ; Tue, 13 Mar 2012 09:31:37 -0700 (PDT) In-Reply-To: <4F5F098E.4040006@ti.com> (Santosh Shilimkar's message of "Tue, 13 Mar 2012 14:17:10 +0530") Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Santosh Shilimkar Cc: linux-omap@vger.kernel.org, dave.long@linaro.org, linux-arm-kernel@lists.infradead.org Santosh Shilimkar writes: > On Monday 12 March 2012 10:21 PM, Kevin Hilman wrote: >> Santosh Shilimkar writes: >> >>> On OMAP4, recently a synchronisation bug is discovered by hardware >>> team, which leads to incorrect timer value read from 32K sync timer >>> IP when the IP is comming out of idle. >>> >>> The issue is due to the synchronization methodology used in the SYNCTIMER IP. >>> The value of the counter register in 32kHz domain is synchronized to the OCP >>> domain register only at count up event, and if the OCP clock is switched off, >>> the OCP register gets out of synch until the first count up event after the >>> clock is switched back -at the next falling edge of the 32kHz clock. >>> >>> Further investigation revealed that it applies to gptimer1 and watchdog timer2 >>> as well which may run on 32KHz. This patch fixes the issue for all the >>> applicable modules. >> >> The changelog describes the problem ver well, but doesn't actually >> describe the fix (enable static dep.) Can you update the changelog do >> describe the fix, and why it fixes the problem. >> > Sure. Updated patch below. The idea is to ensure that synctimer is > syncronised before software does any reads on the counter. The BUG > will get fixed in future OMAP designs Thanks for the updated changelog. Since this doesn't qualify as a regression, queuing for v3.4 (branch: for_3.4/fixes/pm) Kevin