From 0b466dc238cb660bbdb9ef6e121e1757057484c3 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 19 Nov 2015 09:58:05 +0000 Subject: [PATCH] drm/i915: Mark uneven memory banks on gen4 desktop as unknown swizzling MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit We have varied reports of swizzling corruption on gen4 desktop, and confirmation that one at least is triggered by uneven memory banks (L-shaped memory). The implication is that the swizzling varies between the paired channels and the remainder of memory on the single channel. As the object then has unpredictable swizzling (it will vary depending on exact page allocation and may even change during the object's lifetime as the pages are replaced), we have to report to userspace that the swizzling is unknown. However, some existing userspace is buggy when it meets an unknown swizzling configuration and so we need to tell another white lie and mark the swizzling as NONE but report it as UNKNOWN through the extended get-tiling-ioctl. See commit 5eb3e5a5e11d14f9deb2a4b83555443b69ab9940 Author: Chris Wilson Date: Sun Jun 28 09:19:26 2015 +0100 drm/i915: Declare the swizzling unknown for L-shaped configurations for the previous example where we found that telling the truth to userspace just ends up in a world of hurt. Also since we don't truly know what the swizzling is on the pages, we need to keep them pinned to prevent swapping as the reports also suggest that some gen4 devices have previously undetected bit17 swizzling. v2: Combine unknown + quirk patches to prevent userspace ever seeing unknown swizzling through the normal get-tiling-ioctl. Also use the same path for the existing uneven bank detection for mobile gen4. Reported-by: Matti Hämäläinen Tested-by: Matti Hämäläinen References: https://bugs.freedesktop.org/show_bug.cgi?id=90725 Signed-off-by: Chris Wilson Cc: Matti Hämäläinen Cc: Daniel Vetter Cc: Jani Nikula Cc: stable@vger.kernel.org Reviewed-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/1447927085-31726-1-git-send-email-chris@chris-wilson.co.uk Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/i915_gem_fence.c | 36 ++++++++++++++++++++------- 1 file changed, 27 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c index 40a10b25956c..f010391b87f5 100644 --- a/drivers/gpu/drm/i915/i915_gem_fence.c +++ b/drivers/gpu/drm/i915/i915_gem_fence.c @@ -642,11 +642,10 @@ i915_gem_detect_bit_6_swizzle(struct drm_device *dev) } /* check for L-shaped memory aka modified enhanced addressing */ - if (IS_GEN4(dev)) { - uint32_t ddc2 = I915_READ(DCC2); - - if (!(ddc2 & DCC2_MODIFIED_ENHANCED_DISABLE)) - dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES; + if (IS_GEN4(dev) && + !(I915_READ(DCC2) & DCC2_MODIFIED_ENHANCED_DISABLE)) { + swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN; + swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN; } if (dcc == 0xffffffff) { @@ -675,16 +674,35 @@ i915_gem_detect_bit_6_swizzle(struct drm_device *dev) * matching, which was the case for the swizzling required in * the table above, or from the 1-ch value being less than * the minimum size of a rank. + * + * Reports indicate that the swizzling actually + * varies depending upon page placement inside the + * channels, i.e. we see swizzled pages where the + * banks of memory are paired and unswizzled on the + * uneven portion, so leave that as unknown. */ - if (I915_READ16(C0DRB3) != I915_READ16(C1DRB3)) { - swizzle_x = I915_BIT_6_SWIZZLE_NONE; - swizzle_y = I915_BIT_6_SWIZZLE_NONE; - } else { + if (I915_READ16(C0DRB3) == I915_READ16(C1DRB3)) { swizzle_x = I915_BIT_6_SWIZZLE_9_10; swizzle_y = I915_BIT_6_SWIZZLE_9; } } + if (swizzle_x == I915_BIT_6_SWIZZLE_UNKNOWN || + swizzle_y == I915_BIT_6_SWIZZLE_UNKNOWN) { + /* Userspace likes to explode if it sees unknown swizzling, + * so lie. We will finish the lie when reporting through + * the get-tiling-ioctl by reporting the physical swizzle + * mode as unknown instead. + * + * As we don't strictly know what the swizzling is, it may be + * bit17 dependent, and so we need to also prevent the pages + * from being moved. + */ + dev_priv->quirks |= QUIRK_PIN_SWIZZLED_PAGES; + swizzle_x = I915_BIT_6_SWIZZLE_NONE; + swizzle_y = I915_BIT_6_SWIZZLE_NONE; + } + dev_priv->mm.bit_6_swizzle_x = swizzle_x; dev_priv->mm.bit_6_swizzle_y = swizzle_y; } -- 2.20.1