From bc8f2f5db9d75e7f990fb8362c28a8d2a7f33c9c Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 8 Feb 2018 07:28:00 +0000 Subject: [PATCH] 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 Cc: Mika Kuoppala Cc: Joonas Lahtinen Link: https://patchwork.freedesktop.org/patch/msgid/20180208072800.595-1-chris@chris-wilson.co.uk Reviewed-by: Mika Kuoppala --- drivers/gpu/drm/i915/intel_uncore.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c index 4075010ac088..db441bf3b9d5 100644 --- a/drivers/gpu/drm/i915/intel_uncore.c +++ b/drivers/gpu/drm/i915/intel_uncore.c @@ -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); -- 2.30.2