Re: [PATCH] drm/i915: PIPE_CONTROL TLB invalidation fix

From: Daniel Vetter <daniel@ffwll.ch>
To: Ben Widawsky <ben@bwidawsk.net>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: PIPE_CONTROL TLB invalidation fix
Date: Fri, 27 Jul 2012 07:17:36 +0200	[thread overview]
Message-ID: <20120727051736.GA5392@phenom.ffwll.local> (raw)
In-Reply-To: <1343346523-25255-1-git-send-email-ben@bwidawsk.net>

On Thu, Jul 26, 2012 at 04:48:43PM -0700, Ben Widawsky wrote:
> The IVB simulator really doesn't like a TLB invalidate with no post-sync
> operation, in fact it blows up in an assertion failure. The
> documentation states that we must issue the TLB invalidate with a CS
> stall: "Also Requires stall bit ([20] of DW1) set." This patch doesn't
> comply with the docs, but we're able to satisfy the simulator with this
> very small change, and I think simulator has historically trumped docs.
> 
> Note, I don't think this belongs in stable as our TLB invalidation
> should be correct since we use the global invalidation per batch. Using
> TLB invalidation is itself only a requirement of HW contexts.
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

I have another patch from Chris that kills the non-zero post-sync op
workaround for ivb ... So I guess we can't do this this easily.
-Daniel
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index c58f1b9..339712a 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -198,8 +198,12 @@ intel_emit_post_sync_nonzero_flush(struct intel_ring_buffer *ring)
>  	if (ret)
>  		return ret;
>  
> +	/* NOTE: we want the TLB invalidate for render ring flush, but it must
> +	 * be sent with a non-zero post sync op. So it can be stuffed in here
> +	 * for convenience.
> +	 */
>  	intel_ring_emit(ring, GFX_OP_PIPE_CONTROL(5));
> -	intel_ring_emit(ring, PIPE_CONTROL_QW_WRITE);
> +	intel_ring_emit(ring, PIPE_CONTROL_QW_WRITE | PIPE_CONTROL_TLB_INVALIDATE);
>  	intel_ring_emit(ring, scratch_addr | PIPE_CONTROL_GLOBAL_GTT); /* address */
>  	intel_ring_emit(ring, 0);
>  	intel_ring_emit(ring, 0);
> @@ -225,10 +229,10 @@ gen6_render_ring_flush(struct intel_ring_buffer *ring,
>  
>  	/* Just flush everything.  Experiments have shown that reducing the
>  	 * number of bits based on the write domains has little performance
> -	 * impact.
> +	 * impact. Note to copy/pasters: the TLB invlidate we want is tucked
> +	 * into intel_emit_post_sync_nonzero_flush().
>  	 */
>  	flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
> -	flags |= PIPE_CONTROL_TLB_INVALIDATE;
>  	flags |= PIPE_CONTROL_INSTRUCTION_CACHE_INVALIDATE;
>  	flags |= PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE;
>  	flags |= PIPE_CONTROL_DEPTH_CACHE_FLUSH;
> -- 
> 1.7.11.3
> 
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-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48