[Bug 75502] [SNB, IVB] Page flips hang indefinitely, apparently waiting for mmio writes that never happen

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=75502

--- Comment #22 from Simon Farnsworth <simon at farnz.org.uk> ---
(In reply to comment #21)
> To double check the theory that the scanout went awol, can you please try
> with
> 
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c
> b/drivers/gpu/drm/i915/i915_debugfs.c
> index 94aabfc63c3d..c6b81e59058d 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -611,16 +611,28 @@ static int i915_gem_pageflip_info(struct seq_file *m,
> void *data)
>                                 seq_puts(m, "Stall check waiting for page
> flip ioctl, ");
>                         seq_printf(m, "%d prepares\n",
> atomic_read(&work->pending));
>  
> +                       {
> +                               u32 addr;
> +
> +                               if (INTEL_INFO(dev)->gen >= 4)
> +                                       addr = DSPSURF(crtc->plane);
> +                               else
> +                                       addr = DSPADDR(crtc->plane);
> +
> +                               seq_printf(m, "Current scanout address
> 0x%08lx\n", 
> +                                          I915_READ(addr));
> +                       }
> +
>                         if (work->old_fb_obj) {
>                                 struct drm_i915_gem_object *obj =
> work->old_fb_obj;
> -                               seq_printf(m, "Old framebuffer gtt_offset
> 0x%08lx\n",
> +                               seq_printf(m, "Old framebuffer address
> 0x%08lx\n",
>                                            i915_gem_obj_ggtt_offset(obj));
>                         }
>                         if (work->pending_flip_obj) {
>                                 struct drm_i915_gem_object *obj =
> work->pending_flip_obj;
>                                 bool complete;
>  
> -                               seq_printf(m, "New framebuffer gtt_offset
> 0x%08lx\n",
> +                               seq_printf(m, "New framebuffer address
> 0x%08lx\n",
>                                            i915_gem_obj_ggtt_offset(obj));
>  
>                                 if (INTEL_INFO(dev)->gen >= 4) {


I've got a broken machine; with this patch, I see:

Flip queued on pipe A (plane A)
Flip queued on frame 15324, now 3420744
Stall check enabled, 1 prepares
Current scanout address 0x00372000
Old framebuffer address 0x00372000
New framebuffer address 0x00684000
MMIO update completed? 0
No flip due on pipe B (plane B)

I'm going to keep the machine in broken state until you tell me otherwise.

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