[Nouveau] [PATCH] drm/nouveau: Fix pre-nv50 pageflip events (v2)

[Ilia Mirkin]

On Mon, Nov 9, 2015 at 7:57 AM, Mario Kleiner
<mario.kleiner.de at gmail.com> wrote:
> From: Daniel Vetter <daniel.vetter at ffwll.ch>
>
> Apparently pre-nv50 pageflip events happen before the actual vblank
> period. Therefore that functionality got semi-disabled in
>
> commit af4870e406126b7ac0ae7c7ce5751f25ebe60f28
> Author: Mario Kleiner <mario.kleiner.de at gmail.com>
> Date:   Tue May 13 00:42:08 2014 +0200
>
>     drm/nouveau/kms/nv04-nv40: fix pageflip events via special case.
>
> Unfortunately that hack got uprooted in
>
> commit cc1ef118fc099295ae6aabbacc8af94d8d8885eb
> Author: Thierry Reding <treding at nvidia.com>
> Date:   Wed Aug 12 17:00:31 2015 +0200
>
>     drm/irq: Make pipe unsigned and name consistent
>
> Trigering a warning when trying to sample the vblank timestamp for a
> non-existing pipe. There's a few ways to fix this:
>
> - Open-code the old behaviour, which just enshrines this slight
>   breakage of the userspace ABI.
>
> - Revert Mario's commit and again inflict broken timestamps, again not
>   pretty.
>
> - Fix this for real by delaying the pageflip TS until the next vblank
>   interrupt, thereby making it accurate.
>
> This patch implements the third option. Since having a page flip
> interrupt that happens when the pageflip gets armed and not when it
> completes in the next vblank seems to be fairly common (older i915 hw
> works very similarly) create a new helper to arm vblank events for
> such drivers.
>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=106431
> Cc: Thierry Reding <treding at nvidia.com>
> Cc: Mario Kleiner <mario.kleiner.de at gmail.com>
> Cc: Ben Skeggs <bskeggs at redhat.com>
> Cc: Ilia Mirkin <imirkin at alum.mit.edu>
>
> v2 (mario): Integrate my own review comments into Daniels patch.
>    - Fix function prototypes in drmP.h
>    - Add missing vblank_put() for pageflip completion without
>      pageflip event.
>    - Initialize sequence number for queued pageflip event to avoid
>      trouble in drm_handle_vblank_events().
>    - Remove dead code and spelling fix.
>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> Reviewed-by: Mario Kleiner <mario.kleiner.de at gmail.com>

Without commenting on the actual patch, a few points of procedure:

(a) If you're sending the patch, you're supposed to add your
Signed-off-by. So you'd keep Daniel's and add yours.
(b) Since this is triggering warns for real people in real situations,
tack on a

Cc: stable at vger.kernel.org # v4.3

Cheers,

  -ilia