Patch "drm/i915: Declare the swizzling unknown for L-shaped configurations" has been added to the 4.1-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

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

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-i915-declare-the-swizzling-unknown-for-l-shaped-configurations.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 19ee835cdb0b5a8eb11a68f25a51b8039d564488 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 29 Jun 2015 14:01:19 +0100
Subject: drm/i915: Declare the swizzling unknown for L-shaped configurations

From: Chris Wilson <chris@chris-wilson.co.uk>

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@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/i915/i915_gem_tiling.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- 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
 		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) {


Patches currently in stable-queue which might be from chris@chris-wilson.co.uk are

queue-4.1/drm-i915-declare-the-swizzling-unknown-for-l-shaped-configurations.patch
queue-4.1/drm-i915-fix-backlight-after-resume-on-855gm.patch
queue-4.1/revert-drm-i915-declare-the-swizzling-unknown-for-l-shaped-configurations.patch
queue-4.1/drm-stop-resetting-connector-state-to-unknown.patch
queue-4.1/drm-i915-snapshot-seqno-of-most-recently-submitted-request.patch
queue-4.1/drm-i915-use-two-32bit-reads-for-select-64bit-reg_read-ioctls.patch