drm/i915: Enforce that CS packets are qword aligned

We require the caller to ensure that the packets they wish to emit into
the CS ring are qword aligned (i.e. have an even number of dwords).
Double check this.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170721161101.1618-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 5224b7abb8a3d0a462a2b89ff46edbc1d646def7..cdf084ef5aaeaf5e575d6e607577c2af03b01ab2 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1712,6 +1712,9 @@ u32 *intel_ring_begin(struct drm_i915_gem_request *req,
        unsigned int total_bytes;
        u32 *cs;
 
+       /* Packets must be qword aligned. */
+       GEM_BUG_ON(num_dwords & 1);
+
        total_bytes = bytes + req->reserved_space;
        GEM_BUG_ON(total_bytes > ring->effective_size);