[Bug 68718] [snb] vsync hang

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=68718

--- Comment #23 from Ilia Mirkin <imirkin at alum.mit.edu> ---
(In reply to comment #20)
> Guessing now, but maybe try this delta patch on top:
> 
> diff --git a/src/sna/sna_display.c b/src/sna/sna_display.c
> index 99afbd1..2620669 100644
> --- a/src/sna/sna_display.c
> +++ b/src/sna/sna_display.c
> @@ -3984,7 +3984,7 @@ static bool sna_emit_wait_for_scanline_gen6(struct sna
> *sna,
>         b = kgem_get_batch(&sna->kgem);
>  
>         /* Both the LRI and WAIT_FOR_EVENT must be in the same cacheline */
> -       if (((sna->kgem.nbatch + 6) >> 4) != (sna->kgem.nbatch + 9) >> 4) {
> +       if (((sna->kgem.nbatch + 6) >> 3) != (sna->kgem.nbatch + 10) >> 3) {

I also tried leaving this at >> 4 (but with the +10)

>                 int dw = sna->kgem.nbatch + 6;
>                 dw = ALIGN(dw, 16) - dw;

And I tried making this ALIGN(..., 8) with the >> 3 shift

>                 while (dw--)
> 
> 
> I think the cacheline it mentions is 64bytes, but we may as check against
> 32bytes just in case.

In all the cases, I was able to reproduce

[112535.225840] [drm:ring_stuck] *ERROR* Kicking stuck wait on render ring

Every so often I also got

[117822.524434] [drm] no progress on render ring
[117822.524482] [drm:i915_set_reset_status] *ERROR* render ring hung flushing
bo (0x60e000 ctx 0) at 0x1de05ce4

But my understanding is that this is unrelated to the issue at hand.

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