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

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On 11/09/2015 02:02 PM, Ilia Mirkin wrote:
On Mon, Nov 9, 2015 at 7:57 AM, Mario Kleiner
<mario.kleiner.de@xxxxxxxxx> wrote:
From: Daniel Vetter <daniel.vetter@xxxxxxxx>

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@xxxxxxxxx>
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@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
Cc: Ben Skeggs <bskeggs@xxxxxxxxxx>
Cc: Ilia Mirkin <imirkin@xxxxxxxxxxxx>

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@xxxxxxxxx>
Reviewed-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>

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.

I thought my tiny fixes didn't warrant adding a signed off by myself, but if that was wrong, consider it added:

v2: Signed-off-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>

(b) Since this is triggering warns for real people in real situations,
tack on a

Cc: stable@xxxxxxxxxxxxxxx # v4.3


Ah, sorry, this is already a problem in a released kernel? I thought this was something new and so far only for drm-next.

ciao,
-mario

Cheers,

   -ilia

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