On Thu, Nov 19, 2015 at 09:58:05AM +0000, Chris Wilson wrote: > 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 <chris@xxxxxxxxxxxxxxxxxx> > 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 <ccr@xxxxxxxx> > Tested--by: Matti Hämäläinen <ccr@xxxxxxxx> > References: https://bugs.freedesktop.org/show_bug.cgi?id=90725 > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: Matti Hämäläinen <ccr@xxxxxxxx> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> > Cc: Jani Nikula <jani.nikula@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > --- > 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; > } > -- > 2.6.2 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html