From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757719AbaHGMyo (ORCPT ); Thu, 7 Aug 2014 08:54:44 -0400 Received: from cantor2.suse.de ([195.135.220.15]:34770 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757478AbaHGMyn (ORCPT ); Thu, 7 Aug 2014 08:54:43 -0400 Date: Thu, 7 Aug 2014 14:54:41 +0200 (CEST) From: Jiri Kosina To: Pavel Machek cc: "Rafael J. Wysocki" , Linux-pm mailing list , kernel list , Chris Wilson , intel-gfx Subject: Re: 3.15-rc: regression in suspend In-Reply-To: Message-ID: References: <20140607120614.GB5309@amd.pavel.ucw.cz> <20140607231124.GA3611@amd.pavel.ucw.cz> <20140609102328.GA25332@amd.pavel.ucw.cz> <20140625223522.GA5923@xo-6d-61-c0.localdomain> <20140707083908.GE5821@phenom.ffwll.local> <20140711192629.GA20015@amd.pavel.ucw.cz> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 7 Aug 2014, Jiri Kosina wrote: > The patch below seems to finally cure the problem at my system; I've just > attached it to freedesktop bugzilla, but sending it to this thread as well > to hopefully get as much testing coverage by affected people as possible. > > I am going on with testing whether it really completely fixes the problem > or just made it less likely. Okay, after 31 suspend-resume cycles, the problem appeared again (while without the patch, it triggers with 100% reliability). So it's not a complete fix, it just makes the problem much less visible. Going back to bugzilla discussion. > > From: Jiri Kosina > Subject: [PATCH] drm/i915: read HEAD register back in init_ring_common() to enforce ordering > > Withtout this, ring initialization fails reliabily during resume with > > [drm:init_ring_common] *ERROR* render ring initialization failed ctl 0001f001 head ffffff8804 tail 00000000 start 000e4000 > > Signed-off-by: Jiri Kosina > --- > drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c > index 279488a..7add7ee 100644 > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c > @@ -517,6 +517,9 @@ static int init_ring_common(struct intel_engine_cs *ring) > else > ring_setup_phys_status_page(ring); > > + /* Enforce ordering by reading HEAD register back */ > + I915_READ_HEAD(ring); > + > /* Initialize the ring. This must happen _after_ we've cleared the ring > * registers with the above sequence (the readback of the HEAD registers > * also enforces ordering), otherwise the hw might lose the new ring -- Jiri Kosina SUSE Labs