Re: [PATCH 03/13] drm/i915: Record the position of the workarounds in the tail of the request

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Rather than blindly assuming we need to advance the tail for
> resubmitting the request via the ELSP, record the position.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

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

> ---
>  drivers/gpu/drm/i915/i915_gem_request.h | 15 +++++++++------
>  drivers/gpu/drm/i915/intel_lrc.c        |  4 ++--
>  2 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
> index 91014de8bfbc..2faa3bb4c39b 100644
> --- a/drivers/gpu/drm/i915/i915_gem_request.h
> +++ b/drivers/gpu/drm/i915/i915_gem_request.h
> @@ -88,20 +88,23 @@ struct drm_i915_gem_request {
>  	 */
>  	u32 previous_seqno;
>  
> -	/** Position in the ringbuffer of the start of the request */
> +	/** Position in the ring of the start of the request */
>  	u32 head;
>  
>  	/**
> -	 * Position in the ringbuffer of the start of the postfix.
> -	 * This is required to calculate the maximum available ringbuffer
> -	 * space without overwriting the postfix.
> +	 * Position in the ring of the start of the postfix.
> +	 * This is required to calculate the maximum available ring space
> +	 * without overwriting the postfix.
>  	 */
>  	u32 postfix;
>  
> -	/** Position in the ringbuffer of the end of the whole request */
> +	/** Position in the ring of the end of the whole request */
>  	u32 tail;
>  
> -	/** Preallocate space in the ringbuffer for the emitting the request */
> +	/** Position in the ring of the end of any workarounds after the tail */
> +	u32 wa_tail;
> +
> +	/** Preallocate space in the ring for the emitting the request */
>  	u32 reserved_space;
>  
>  	/**
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index ca52b8e63305..25e0972e7166 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -482,8 +482,7 @@ static void execlists_unqueue(struct intel_engine_cs *engine)
>  		 * resubmit the request. See gen8_emit_request() for where we
>  		 * prepare the padding after the end of the request.
>  		 */
> -		req0->tail += 8;
> -		req0->tail &= req0->ring->size - 1;
> +		req0->tail = req0->wa_tail;
>  	}
>  
>  	execlists_elsp_submit_contexts(req0, req1);
> @@ -711,6 +710,7 @@ intel_logical_ring_advance(struct drm_i915_gem_request *request)
>  	intel_ring_emit(ring, MI_NOOP);
>  	intel_ring_emit(ring, MI_NOOP);
>  	intel_ring_advance(ring);
> +	request->wa_tail = ring->tail;
>  
>  	/* We keep the previous context alive until we retire the following
>  	 * request. This ensures that any the context object is still pinned
> -- 
> 2.9.3
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