[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-ckt5.

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 557d03ad3affaf6869db5f5d22cb790c4f31d07e Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris at chris-wilson.co.uk>
Date: Mon, 29 Jun 2015 14:01:19 +0100
Subject: drm/i915: Declare the swizzling unknown for L-shaped configurations

commit 19ee835cdb0b5a8eb11a68f25a51b8039d564488 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 objects.

v2: Mark the global swizzling as unknown rather than adjust the value
reported to userspace.

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>
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 | 12 +++++++++++-
 1 file changed, 11 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..8ce8c5e 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -183,8 +183,18 @@ i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
 		if (IS_GEN4(dev)) {
 			uint32_t ddc2 = I915_READ(DCC2);

-			if (!(ddc2 & DCC2_MODIFIED_ENHANCED_DISABLE))
+			if (!(ddc2 & DCC2_MODIFIED_ENHANCED_DISABLE)) {
+				/* Since the swizzling may vary within an
+				 * object, we have no idea what the swizzling
+				 * is for any page in particular. Thus we
+				 * cannot migrate tiled pages using the GPU,
+				 * nor can we tell userspace what the exact
+				 * swizzling is for any object.
+				 */
 				dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES;
+				swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
+				swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
+			}
 		}

 		if (dcc == 0xffffffff) {
--
1.9.1