Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030796Ab2HQDcU (ORCPT ); Thu, 16 Aug 2012 23:32:20 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:46798 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030663Ab2HQD1B (ORCPT ); Thu, 16 Aug 2012 23:27:01 -0400 Message-Id: <20120817030248.892667316@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Fri, 17 Aug 2012 04:03:15 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Daniel Vetter , Jani Nikula , Yang Guang Subject: [ 32/37] drm/i915: correctly order the ring init sequence In-Reply-To: <20120817030243.807605523@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2091 Lines: 54 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Vetter commit 0d8957c8a90bbb5d34fab9a304459448a5131e06 upstream. We may only start to set up the new register values after having confirmed that the ring is truely off. Otherwise the hw might lose the newly written register values. This is caught later on in the init sequence, when we check whether the register writes have stuck. Reviewed-by: Jani Nikula Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50522 Tested-by: Yang Guang Signed-off-by: Daniel Vetter Signed-off-by: Ben Hutchings --- drivers/gpu/drm/i915/intel_ringbuffer.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index bf0195a..414af1e 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -289,8 +289,6 @@ static int init_ring_common(struct intel_ring_buffer *ring) I915_WRITE_HEAD(ring, 0); ring->write_tail(ring, 0); - /* Initialize the ring. */ - I915_WRITE_START(ring, obj->gtt_offset); head = I915_READ_HEAD(ring) & HEAD_ADDR; /* G45 ring initialization fails to reset head to zero */ @@ -316,6 +314,11 @@ static int init_ring_common(struct intel_ring_buffer *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 + * register values. */ + I915_WRITE_START(ring, obj->gtt_offset); I915_WRITE_CTL(ring, ((ring->size - PAGE_SIZE) & RING_NR_PAGES) | RING_VALID); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/