[Intel-gfx] [PATCH v5] drm/i915: Emit to ringbuffer directly

[Chris Wilson]

Just recording a couple of BUG_ON for posterity, would be nice additions
to this patch:

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 11d355d314e1..702c023cd502 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2264,6 +2264,7 @@ u32 *intel_ring_begin(struct drm_i915_gem_request *req, int num_dwords)
                ring->space -= remain_actual;
        }
 
+       GEM_BUG_ON(ring->tail > ring->size - bytes);
        out = (u32 *)(ring->vaddr + ring->tail);
        ring->tail += bytes;
        ring->space -= bytes;

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 896838ca502c..117e1e735fc7 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -526,6 +526,7 @@ static inline u32 intel_ring_offset(struct intel_ring *ring, void *addr)
 {
        /* Don't write ring->size (equivalent to 0) as that hangs some GPUs. */
        u32 offset = addr - ring->vaddr;
+       GEM_BUG_ON(offset > ring->size);
        return offset & (ring->size - 1);
 }


On Wed, Feb 08, 2017 at 02:14:34PM +0000, Tvrtko Ursulin wrote:
> @@ -862,10 +863,9 @@ void __i915_add_request(struct drm_i915_gem_request *request, bool flush_caches)
>  	 * GPU processing the request, we never over-estimate the
>  	 * position of the ring's HEAD.
>  	 */
> -	err = intel_ring_begin(request, engine->emit_breadcrumb_sz);
> -	GEM_BUG_ON(err);
>  	request->postfix = ring->tail;
> -	ring->tail += engine->emit_breadcrumb_sz * sizeof(u32);
> +	out = intel_ring_begin(request, engine->emit_breadcrumb_sz);
> +	GEM_BUG_ON(IS_ERR(out));

A test for BAT :)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre