[3.8.y.z extended stable] Patch "drm/i915: Prevent MI_DISPLAY_FLIP straddling two cachelines on IVB" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    drm/i915: Prevent MI_DISPLAY_FLIP straddling two cachelines on IVB

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.20.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From 9a04278fb4699dab3e69ec6a681d355973c68de5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala at linux.intel.com>
Date: Tue, 11 Feb 2014 19:52:06 +0200
Subject: drm/i915: Prevent MI_DISPLAY_FLIP straddling two cachelines on IVB
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit f66fab8e1cd6b3127ba4c5c0d11539fbe1de1e36 upstream.

According to BSpec the entire MI_DISPLAY_FLIP packet must be contained
in a single cacheline. Make sure that happens.

v2: Use intel_ring_begin_cacheline_safe()
v3: Use intel_ring_cacheline_align() (Chris)

Cc: Bjoern C <lkml at call-home.ch>
Cc: Alexandru DAMIAN <alexandru.damian at intel.com>
Cc: Enrico Tagliavini <enrico.tagliavini at gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=74053
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/i915/intel_display.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7330c58..ad2b52e 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7387,6 +7387,20 @@ static int intel_gen7_queue_flip(struct drm_device *dev,
 		goto err_unpin;
 	}

+	/*
+	 * BSpec MI_DISPLAY_FLIP for IVB:
+	 * "The full packet must be contained within the same cache line."
+	 *
+	 * Currently the LRI+SRM+MI_DISPLAY_FLIP all fit within the same
+	 * cacheline, if we ever start emitting more commands before
+	 * the MI_DISPLAY_FLIP we may need to first emit everything else,
+	 * then do the cacheline alignment, and finally emit the
+	 * MI_DISPLAY_FLIP.
+	 */
+	ret = intel_ring_cacheline_align(ring);
+	if (ret)
+		goto err_unpin;
+
 	ret = intel_ring_begin(ring, 4);
 	if (ret)
 		goto err_unpin;
--
1.8.3.2