From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH] gpio/omap: fix invalid context restore of gpio bank-0 Date: Mon, 2 Jul 2012 13:26:38 -0500 Message-ID: <4FF1E7DE.10409@ti.com> References: <1340990551-19426-1-git-send-email-jon-hunter@ti.com> <87mx3i595b.fsf@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from arroyo.ext.ti.com ([192.94.94.40]:58137 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752478Ab2GBS07 (ORCPT ); Mon, 2 Jul 2012 14:26:59 -0400 In-Reply-To: <87mx3i595b.fsf@ti.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Kevin Hilman Cc: linux-omap , linux-arm , Grant Likely , Linus Walleij , Tarun Kanti DebBarma , Franky Lin , NeilBrown On 07/02/2012 01:07 PM, Kevin Hilman wrote: > + Neil Brown > > Hi Jon, > > Jon Hunter writes: > >> Currently the gpio _runtime_resume/suspend functions are calling the >> get_context_loss_count() platform function if the function is populated for >> a gpio bank. This function is used to determine if the gpio bank logic state >> needs to be restored due to a power transition. This function will be populated >> for all banks, but it should only be called for banks that have the >> "loses_context" variable set. It is pointless to call this if loses_context is >> false as we know the context will never be lost and will not need restoring. >> >> For all OMAP2+ devices gpio bank-0 is in an always-on power domain and so will >> never lose context. We found that the get_context_loss_count() was being called >> for bank-0 during the probe and returning 1 instead of 0 indicating that the >> context had been lost. This was causing the context restore function to be >> called at probe time for this bank and because the context had never been saved, >> was restoring an invalid state. This ultimately resulted in a crash [1]. >> >> There are multiple bugs here that need to be addressed ... >> >> 1. Why the always-on power domain returns a context loss count of 1? This needs >> to be fixed in the power domain code. However, the gpio driver should not >> assume the loss count is 0 to begin with. >> 2. The omap gpio driver should never be calling get_context_loss_count for a >> gpio bank in a always-on domain. This is pointless and adds unneccessary >> overhead. >> 3. The OMAP gpio driver assumes that the initial power domain context loss count >> will be 0 at the time the gpio driver is probed. However, it could be >> possible that this is not the case and an invalid context restore could be >> performed during the probe. To avoid this otherwise only populated the > > The 'To avoid this...' sentence here doesn't read well. Looks like you > need to: > > s/otherwise// Yes, I meant to have dropped "otherwise" here. Thanks! > s/populated/populate/ Yes that too! I must have re-worded and screwed it up royally :-( > ? > >> get_context_loss_count() function pointer after the initial call to >> pm_runtime_get() has occurred. This will ensure that the first >> pm_runtime_put() initialised the loss count correctly. >> >> This patch addresses issues 2 and 3 above. >> [1] http://marc.info/?l=linux-omap&m=134065775323775&w=2 >> >> Cc: Grant Likely >> Cc: Linus Walleij >> Cc: Kevin Hilman >> Cc: Tarun Kanti DebBarma >> Cc: Franky Lin >> >> Reported-by: Franky Lin >> Signed-off-by: Jon Hunter > > Thanks for digging inot this bug Jon. The same bug was brought up by > Neil Brown (Cc'd) in a different thread. > > Neil, it looks to me that this fix will address the problems you were > seeing as well. Care to test, and respond with your ack/tested-by if it > works for you? Thanks. Neil let me know your thoughts and if you are ok, I can clean-up the changelog and re-send. Cheers Jon