[Bug 76554] [gm45 regression] [drm:init_ring_common]: *ERROR* render ring initialization failed

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=76554

--- Comment #46 from Chris Wilson <chris at chris-wilson.co.uk> ---
(In reply to comment #45)
> (In reply to comment #44)
> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > index 5a74986348c6..b46b3e928a7f 100644
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > @@ -530,6 +530,17 @@ static int init_ring_common(struct intel_ring_buffer
> > *ring)
> >                         ((ring->size - PAGE_SIZE) & RING_NR_PAGES)
> >                         | RING_VALID);
> >  
> > +       if (I915_READ_START(ring) != i915_gem_obj_ggtt_offset(obj)) {
> > +               printk(KERN_ERR
> > +                      "%s initialization failed"
> > +                      " [%08x != %08x], fudging\n",
> > +                      ring->name,
> > +                      I915_READ_START(ring),
> > +                      i915_gem_obj_ggtt_offset(obj));
> > +               I915_WRITE_START(ring, i915_gem_obj_ggtt_offset(obj));
> > +               POSTING_READ(ring);
> > +       }
> > +
> >         iowrite32(MI_NOOP, ring->virtual_start + 0);
> >         iowrite32(MI_NOOP, ring->virtual_start + 4);
> >         ring->write_tail(ring, 8);
> 
> What is a baseline I should apply this on top of, please? The surrounding
> code in my tree (with all the patches provided so far apples) is
> 
> [ ... ]
>         I915_WRITE_CTL(ring,
>                         ((ring->size - PAGE_SIZE) & RING_NR_PAGES)
>                         | RING_VALID);
>         if (wait_for(I915_READ_CTL(ring) & RING_VALID, 1000)) {
>                 DRM_ERROR("%s initialization failed ctl %08x (valid? %d)\n",
>                                 ring->name,
>                                 I915_READ_CTL(ring),
>                                 !!(I915_READ_CTL(ring) & RING_VALID));
>                 ret = -EIO;
>                 goto out;
>         }
>         I915_WRITE_HEAD(ring, 0);
>         ring->write_tail(ring, 0);
> 
>         iowrite32(MI_NOOP, ring->virtual_start + 0);
>         iowrite32(MI_NOOP, ring->virtual_start + 4);
>         ring->write_tail(ring, 8);
> [ ... ]
> 
> (i.e. it has the extra I915_WRITE_HEAD(ring, 0); ring->write_tail(ring, 0);,
> etc).
> 
> I can of course easily apply the hunk just between the 
> 
>    ring->write_tail(ring, 0);
> 
> and 
> 
>    iowrite32(MI_NOOP, ring->virtual_start + 0);
> 
> if that's what you want me to do.
> 
> Thanks.

Sorry, I threw away the preceding hack to try and keep the diff clean. Just
plonk the write to set HEAD again after setting CTRL (and the wait_for(CTRL) if
you have that).

Hmm, it appears we have drifted slightly in our assortment of patches, let me
push my current collection of hacks so we can rebase.

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