[3.19.y-ckt stable] Patch "drm/i915: Declare the swizzling unknown for L-shaped configurations" 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: Declare the swizzling unknown for L-shaped configurations

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt6.

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

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 15a1ef21b290e431579d56e4551cedeed1191e96 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris at chris-wilson.co.uk>
Date: Sun, 28 Jun 2015 09:19:26 +0100
Subject: drm/i915: Declare the swizzling unknown for L-shaped configurations

commit 5eb3e5a5e11d14f9deb2a4b83555443b69ab9940 upstream.

The old style of memory interleaving swizzled upto the end of the
first even bank of memory, and then used the remainder as unswizzled on
the unpaired bank - i.e. swizzling is not constant for all memory. This
causes problems when we try to migrate memory and so the kernel prevents
migration at all when we detect L-shaped inconsistent swizzling.
However, this issue also extends to userspace who try to manually detile
into memory as the swizzling for an individual page is unknown (it
depends on its physical address only known to the kernel), userspace
cannot correctly swizzle.

Note that this is a new attempt for the previously merged one,
reverted in

commit d82c0ba6e306f079407f07003e53c262d683397b
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Tue Jul 14 12:29:27 2015 +0200

    Revert "drm/i915: Declare the swizzling unknown for L-shaped configurations"

This is cc: stable since we need it to fix up troubles with wc cpu
mmaps that userspace recently started to use widely.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91105
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
[danvet: Add note about previous (failed attempt).]
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/i915/i915_gem_tiling.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index ffe9072..c91d8aa 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -464,7 +464,10 @@ i915_gem_get_tiling(struct drm_device *dev, void *data,
 	}

 	/* Hide bit 17 from the user -- see comment in i915_gem_set_tiling */
-	args->phys_swizzle_mode = args->swizzle_mode;
+	if (dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES)
+		args->phys_swizzle_mode = I915_BIT_6_SWIZZLE_UNKNOWN;
+	else
+		args->phys_swizzle_mode = args->swizzle_mode;
 	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_17)
 		args->swizzle_mode = I915_BIT_6_SWIZZLE_9;
 	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_10_17)
--
1.9.1