drm/i915/gtt: Trust the uncached store to flush wcb

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Not all architectures guarantee that uncached read will
flush the write combining buffer. So marking it explicitly
is recommended [1].

However we know the architecture we are operating on
and can avoid wmb as the UC store will flush the wcb [2].

Omit the wmb() before invalidate as redudant.

v2: squash combining and removal (Chris)
v3: remove obsolete comments about posting reads (Chris)

References: http://yarchive.net/comp/linux/write_combining.html [1]
References: http://download.intel.com/design/PentiumII/applnots/24442201.pdf [2]
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180508124154.14586-1-mika.kuoppala@linux.intel.com

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This commit is contained in:

Mika Kuoppala 2018-05-08 15:41:54 +03:00

parent 429204f105

commit ca6acc2525

1 changed files with 8 additions and 10 deletions

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drivers/gpu/drm/i915/i915_gem_gtt.c

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