[Intel-gfx] [PATCH v2] drm/i915/gt: Flush gen7 even harder

[Mika Kuoppala]

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

> live_blt is still failing on hsw, showing the hallmark of incoherency.
> Since we are fairly certain that the interrupt is after the seqno is
> visible, the other possibility is that the seqno is before the writes to
> memory are flushed. Throw in an TLB invalidate before the breadcrumb as
> we are reasonably confident that forces a CS stall.
>
> References: f9228f765873 ("drm/i915/gt: Try an extra flush on the Haswell blitter")
> 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>
> ---
> Try Mika's suggestion of an invalidate first.
> ---
>  drivers/gpu/drm/i915/gt/intel_ring_submission.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> index fc29df712810..e8bee44add34 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> @@ -454,8 +454,9 @@ 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;
> -	*cs++ = 0;
> +	*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;

If/when it doesn't work, we could try to push the invalidate to both
parts and/or tickle the same cacheline.

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

>  	*cs++ = 0;
>  
>  	*cs++ = MI_FLUSH_DW | MI_FLUSH_DW_OP_STOREDW | MI_FLUSH_DW_STORE_INDEX;
> -- 
> 2.24.0