[Intel-gfx] [PATCH] drm/i915/gt: Invalidate as we write the gen7 breadcrumb

[Mika Kuoppala]

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

> Still the saga of the hsw live_blt incoherency continues. While it did
> seem that the invalidate before the breadcrumb had improved the mtbf,
> nevertheless live_blt still failed. Mika's next idea was to pull the
> invalidate-stall into the breadcrumb write itself.
>
> References: 860afa086841 ("drm/i915/gt: Flush gen7 even harder")
> References: https://bugs.freedesktop.org/show_bug.cgi?id=112147
> Testcase: igt/i915_selftest/live_blt
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_ring_submission.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> index e8bee44add34..f25ceccb335e 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> @@ -454,12 +454,8 @@ static u32 *gen7_xcs_emit_breadcrumb(struct i915_request *rq, u32 *cs)
>  	GEM_BUG_ON(i915_request_active_timeline(rq)->hwsp_ggtt != rq->engine->status_page.vma);
>  	GEM_BUG_ON(offset_in_page(i915_request_active_timeline(rq)->hwsp_offset) != I915_GEM_HWS_SEQNO_ADDR);
>  
> -	*cs++ = (MI_FLUSH_DW | MI_INVALIDATE_TLB |
> -		 MI_FLUSH_DW_STORE_INDEX | MI_FLUSH_DW_OP_STOREDW);
> -	*cs++ = I915_GEM_HWS_SCRATCH_ADDR | MI_FLUSH_DW_USE_GTT;
> -	*cs++ = 0;
> -
> -	*cs++ = MI_FLUSH_DW | MI_FLUSH_DW_OP_STOREDW | MI_FLUSH_DW_STORE_INDEX;
> +	*cs++ = MI_FLUSH_DW | MI_INVALIDATE_TLB |
> +		MI_FLUSH_DW_OP_STOREDW | MI_FLUSH_DW_STORE_INDEX;
>  	*cs++ = I915_GEM_HWS_SEQNO_ADDR | MI_FLUSH_DW_USE_GTT;
>  	*cs++ = rq->fence.seqno;

In both would have been the shotgun approach. You favour sniper.

Acked-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>

>  
> @@ -474,6 +470,7 @@ static u32 *gen7_xcs_emit_breadcrumb(struct i915_request *rq, u32 *cs)
>  	*cs++ = 0;
>  
>  	*cs++ = MI_USER_INTERRUPT;
> +	*cs++ = MI_NOOP;
>  
>  	rq->tail = intel_ring_offset(rq, cs);
>  	assert_ring_tail_valid(rq->ring, rq->tail);
> -- 
> 2.24.0