Commit bc8f2f5d authored Feb 08, 2018 by Chris Wilson

drm/i915: Be paranoid and post the writes to stop the rings



Although the mmio are uncached and so should be flushed on every write,
be paranoid and do a mmio read after setting the ring head/tail to be
sure they have taken effect before moving on.

v2: post tail to be pleasing to the eye

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180208072800.595-1-chris@chris-wilson.co.uk


Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

parent 0d73e7a0

drivers/gpu/drm/i915/intel_uncore.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1522,9 +1522,11 @@ static void gen3_stop_engine(struct intel_engine_cs *engine)
		engine->name);

		I915_WRITE_FW(RING_HEAD(base), I915_READ_FW(RING_TAIL(base)));
		POSTING_READ_FW(RING_HEAD(base)); /* paranoia */

		I915_WRITE_FW(RING_HEAD(base), 0);
		I915_WRITE_FW(RING_TAIL(base), 0);
		POSTING_READ_FW(RING_TAIL(base));

		/* The ring must be empty before it is disabled */
		I915_WRITE_FW(RING_CTL(base), 0);

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