[Intel-gfx] [RFC 1/3] drm/i915: split out uncore_mmio_debug

[Chris Wilson]

Quoting Daniele Ceraolo Spurio (2019-08-08 02:44:21)
> Multiple uncore structures will share the debug infrastructure, so
> move it to a common place and add extra locking around it.
> Also, since we now have a separate object, it is cleaner to have
> dedicated functions working on the object to stop and restart the
> mmio debug. Apart from the cosmetic changes, this patch introduces
> 2 functional updates:
> 
> - All calls to check_for_unclaimed_mmio will now return false when
>   the debug is suspended, not just the ones that are active only when
>   i915_modparams.mmio_debug is set. If we don't trust the result of the
>   check while a user is doing mmio access then we shouldn't attempt the
>   check anywhere.
> 
> - i915_modparams.mmio_debug is not save/restored anymore around user
>   access. The value is now never touched by the kernel while debug is
>   disabled so no need for save/restore.

Yup. Early return from check_for_unclaimed_mmio() if suspended, with
user_forcewake calling mmio_suspend.

> v2: squash mmio_debug patches, restrict mmio_debug lock usage (Chris)
> 
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris