drm/i915: Pad ringbuffer with NOOPs before wrapping

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According to the docs, the ringbuffer is not allowed to wrap in the middle
of an instruction.

G45 PRM, Vol 1b, p101:
  While the “free space” wrap may allow commands to be wrapped around the
  end of the Ring Buffer, the wrap should only occur between commands.
  Padding (with NOP) may be required to follow this restriction.

Do as commanded.

[Having seen bug reports where there is evidence of split commands, but
apparently the GPU has continued on merrily before a bizarre and untimely
death, this may or may not fix a few random hangs.]

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
CC: Eric Anholt <eric@anholt.net>
Signed-off-by: Eric Anholt <eric@anholt.net>

...

This commit is contained in:

Chris Wilson 2009-09-05 18:07:06 +01:00 • committed by Eric Anholt

parent 5e17ee74b5

commit 0ef82af725

4 changed files with 50 additions and 27 deletions

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4

drivers/gpu/drm/i915/i915_debugfs.c

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29

drivers/gpu/drm/i915/i915_dma.c

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41

drivers/gpu/drm/i915/i915_drv.h

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1

drivers/gpu/drm/i915/i915_gem.c

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