On Thu, 19 Nov 2015, Daniel Vetter <daniel@xxxxxxxx> wrote: > 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> Pushed to drm-intel-fixes, thanks for the patch and review. BR, Jani. > >> --- >> 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 >> -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
