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

[Mario Kleiner]

When we are at it, the one with the title "[PATCH] drm/nouveau: Use 
drm_vblank_on/off consistently" from Daniel, which has a reviewed and 
tested by me also never made it into nouveau.

Maybe pick that up as well?

-mario

On 12/01/2015 04:55 PM, Daniel Vetter wrote:
> On Tue, Dec 01, 2015 at 04:08:16PM +0100, poma wrote:
>> On Mon, Nov 16, 2015 at 4:11 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
>>> On Mon, Nov 02, 2015 at 04:45:00PM +0900, Michel Dänzer wrote:
>>>> On 31.10.2015 06:55, Daniel Vetter wrote:
>>>>> 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.
>>>>
>>>> What happens when the page flip interrupt arrives during a vertical
>>>> blank period?  Presumably the userspace event will be deferred until the
>>>> next vertical blank period, but the flip might already take effect in
>>>> the current one.
>>>
>>> Hm yeah there's a tiny race if your update handler for the pageflip can
>>> race with your vblank handler. That's impossible here since it's all done
>>> from the same hw irq hanlder, and since that is single-threaded there
>>> shouldn't be a problem, as long as vblank handling are pageflip are
>>> ordered correctly.
>>>
>>> Might be worth a note in the kerneldoc though that this function isn't
>>> perfectly foolproof.
>>> -Daniel
>>
>>
>> Is there any updates in this respect?
>>
>> drm-nouveau-Fix-pre-nv50-pageflip-events-v4.patch
>> https://patchwork.kernel.org/patch/7591531
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=106431
>> Reported:     2015-10-21
>
> Ben Skeggs asleep probably. Dave, can you pls pick this up?
> -Daniel
>