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Commit 0d8957c8 authored by Daniel Vetter's avatar Daniel Vetter
Browse files

drm/i915: correctly order the ring init sequence 



We may only start to set up the new register values after having
confirmed that the ring is truely off. Otherwise the hw might lose the
newly written register values. This is caught later on in the init
sequence, when we check whether the register writes have stuck.

Cc: stable@vger.kernel.org
Reviewed-by: default avatarJani Nikula <jani.nikula@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50522


Tested-by: default avatarYang Guang <guang.a.yang@intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent da612d88

drivers/gpu/drm/i915/intel_ringbuffer.c

+5 −2
Original line number Diff line number Diff line
@@ -289,8 +289,6 @@ static int init_ring_common(struct intel_ring_buffer *ring) 
	I915_WRITE_HEAD(ring, 0);

	ring->write_tail(ring, 0);



	/* Initialize the ring. */

	I915_WRITE_START(ring, obj->gtt_offset);

	head = I915_READ_HEAD(ring) & HEAD_ADDR;



	/* G45 ring initialization fails to reset head to zero */
@@ -316,6 +314,11 @@ static int init_ring_common(struct intel_ring_buffer *ring) 
		}

	}



	/* Initialize the ring. This must happen _after_ we've cleared the ring

	 * registers with the above sequence (the readback of the HEAD registers

	 * also enforces ordering), otherwise the hw might lose the new ring

	 * register values. */

	I915_WRITE_START(ring, obj->gtt_offset);

	I915_WRITE_CTL(ring,

			((ring->size - PAGE_SIZE) & RING_NR_PAGES)

			| RING_VALID);