linux-kernel - [PATCH 4.1 146/267] Revert "drm/i915: Declare the swizzling unknown for L-shaped configurations"

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Message-Id: <20150731194006.669262380@linuxfoundation.org>
Date:	Fri, 31 Jul 2015 12:39:57 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Harald Arnesen <harald@...gtun.org>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Daniel Vetter <daniel.vetter@...el.com>
Subject: [PATCH 4.1 146/267] Revert "drm/i915: Declare the swizzling unknown for L-shaped configurations"

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Vetter <daniel.vetter@...ll.ch>

commit d82c0ba6e306f079407f07003e53c262d683397b upstream.

This reverts commit 19ee835cdb0b5a8eb11a68f25a51b8039d564488.

It breaks existing old userspace which doesn't handle UNKNOWN
swizzling correct. Yes UNKNOWN was a thing back in 2009 and probably
still is on some other platforms, but it still pretty clearly broke
the testers machine. If we want this we need to extend the ioctl with
new paramters that only new userspace looks at.

Cc: Harald Arnesen <harald@...gtun.org>
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Reported-by: Harald Arnesen <harald@...gtun.org>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -183,18 +183,8 @@ i915_gem_detect_bit_6_swizzle(struct drm
 		if (IS_GEN4(dev)) {
 			uint32_t ddc2 = I915_READ(DCC2);
 
-			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.
-				 */
+			if (!(ddc2 & DCC2_MODIFIED_ENHANCED_DISABLE))
 				dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES;
-				swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
-				swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
-			}
 		}
 
 		if (dcc == 0xffffffff) {


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