This is a note to let you know that I've just added the patch titled
drm/i915: Init PPGTT before context enable
to the 3.18-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-init-ppgtt-before-context-enable.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f48a01651b1758550c4d3ee65ec726dfa0658780 Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Date: Tue, 20 Jan 2015 17:21:42 +0000
Subject: drm/i915: Init PPGTT before context enable
From: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
commit f48a01651b1758550c4d3ee65ec726dfa0658780 upstream.
Commit 82460d972 ("drm/i915: Rework ppgtt init to no require an aliasing
ppgtt") introduced a regression on Broadwell, triggering the following
IOMMU fault at startup:
vgaarb: device changed decodes: PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
dmar: DRHD: handling fault status reg 2
dmar: DMAR:[DMA Write] Request device [00:02.0] fault addr 880000
DMAR:[fault reason 23] Unknown
fbcon: inteldrmfb (fb0) is primary device
Further commentary from Daniel:
I sugggested this change to David after staring at the offending patch
for a while. I have no idea and theory whatsoever why this would upset
the gpu less than the other way round. But it seems to work. David
promised to chase hw people a bit more to get a more meaningful answer.
Wrt the comment that this deletes: I've done some digging and afaict
loading context before ppgtt enable was once required before our recent
restructuring of the context/ppgtt init code: Before that context sw
setup (i.e. allocating the default context) and hw setup was smashed
together. Also the setup of the default context was the bit that
actually allocated the aliasing ppgtt structures. Which is the reason
for the context before ppgtt depency.
Or was, since with all the untangling there's no no real depency any
more (functional, who knows what the hw is doing), so the comment is
just stale.
Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 19 ++++++-------------
1 file changed, 6 insertions(+), 13 deletions(-)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4818,25 +4818,18 @@ i915_gem_init_hw(struct drm_device *dev)
for (i = 0; i < NUM_L3_SLICES(dev); i++)
i915_gem_l3_remap(&dev_priv->ring[RCS], i);
- /*
- * XXX: Contexts should only be initialized once. Doing a switch to the
- * default context switch however is something we'd like to do after
- * reset or thaw (the latter may not actually be necessary for HW, but
- * goes with our code better). Context switching requires rings (for
- * the do_switch), but before enabling PPGTT. So don't move this.
- */
- ret = i915_gem_context_enable(dev_priv);
+ ret = i915_ppgtt_init_hw(dev);
if (ret && ret != -EIO) {
- DRM_ERROR("Context enable failed %d\n", ret);
+ DRM_ERROR("PPGTT enable failed %d\n", ret);
i915_gem_cleanup_ringbuffer(dev);
-
- return ret;
}
- ret = i915_ppgtt_init_hw(dev);
+ ret = i915_gem_context_enable(dev_priv);
if (ret && ret != -EIO) {
- DRM_ERROR("PPGTT enable failed %d\n", ret);
+ DRM_ERROR("Context enable failed %d\n", ret);
i915_gem_cleanup_ringbuffer(dev);
+
+ return ret;
}
return ret;
Patches currently in stable-queue which might be from dwmw2@xxxxxxxxxxxxx are
queue-3.18/drm-i915-init-ppgtt-before-context-enable.patch
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