Re: [PATCH v2 4/6] drm: allow DRM_MODE_PAGE_FLIP_ASYNC for atomic commits
On Tue, 30 Aug 2022 17:29:35 +
Simon Ser wrote:
> If the driver supports it, allow user-space to supply the
> DRM_MODE_PAGE_FLIP_ASYNC flag to request an async page-flip.
> Set drm_crtc_state.async_flip accordingly.
>
> Document that drivers will reject atomic commits if an async
> flip isn't possible. This allows user-space to fall back to
> something else. For instance, Xorg falls back to a blit.
> Another option is to wait as close to the next vblank as
> possible before performing the page-flip to reduce latency.
>
> v2: document new uAPI
>
> Signed-off-by: Simon Ser
> Co-developed-by: André Almeida
> Signed-off-by: André Almeida
> Cc: Daniel Vetter
> Cc: Joshua Ashton
> Cc: Melissa Wen
> Cc: Alex Deucher
> Cc: Harry Wentland
> Cc: Nicholas Kazlauskas
> Cc: Ville Syrjälä
> ---
> drivers/gpu/drm/drm_atomic_uapi.c | 28 +---
> include/uapi/drm/drm_mode.h | 4
> 2 files changed, 29 insertions(+), 3 deletions(-)
...
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 86a292c3185a..cce1a1bea645 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -942,6 +942,10 @@ struct hdr_output_metadata {
> * Request that the page-flip is performed as soon as possible, ie. with no
> * delay due to waiting for vblank. This may cause tearing to be visible on
> * the screen.
> + *
> + * When used with atomic uAPI, the driver will return an error if the
> hardware
> + * doesn't support performing an asynchronous page-flip for this update.
> + * User-space should handle this, e.g. by falling back to a regular
> page-flip.
> */
> #define DRM_MODE_PAGE_FLIP_ASYNC 0x02
> #define DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE 0x4
Hi Simon,
recalling what Ville explained that enabling async flips might require
one more sync flip first, how is that supposed to work?
A TEST_ONLY commit is not allowed to change hardware state, and a
failing real commit is not allowed to change hardware state either
(right?), therefore a failing async flip cannot prepare the next flip
to be async, meaning async will never work.
Thanks,
pq
pgpQjqqQyWKHR.pgp
Description: OpenPGP digital signature
Re: [PATCH v2 4/6] drm: allow DRM_MODE_PAGE_FLIP_ASYNC for atomic commits
On Wednesday, August 31st, 2022 at 09:50, Pekka Paalanen
wrote:
> > diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> > index 86a292c3185a..cce1a1bea645 100644
> > --- a/include/uapi/drm/drm_mode.h
> > +++ b/include/uapi/drm/drm_mode.h
> > @@ -942,6 +942,10 @@ struct hdr_output_metadata {
> > * Request that the page-flip is performed as soon as possible, ie. with no
> > * delay due to waiting for vblank. This may cause tearing to be visible on
> > * the screen.
> > + *
> > + * When used with atomic uAPI, the driver will return an error if the
> > hardware
> > + * doesn't support performing an asynchronous page-flip for this update.
> > + * User-space should handle this, e.g. by falling back to a regular
> > page-flip.
> > */
> > #define DRM_MODE_PAGE_FLIP_ASYNC 0x02
> > #define DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE 0x4
>
> Hi Simon,
>
> recalling what Ville explained that enabling async flips might require
> one more sync flip first, how is that supposed to work?
>
> A TEST_ONLY commit is not allowed to change hardware state, and a
> failing real commit is not allowed to change hardware state either
> (right?), therefore a failing async flip cannot prepare the next flip
> to be async, meaning async will never work.
I'd blame it on bad hw, and make it one special quirk in the driver,
just like it does now.
Ville, thoughts?
Re: [PATCH v2 4/6] drm: allow DRM_MODE_PAGE_FLIP_ASYNC for atomic commits
On Wed, Aug 31, 2022 at 02:56:12PM +, Simon Ser wrote:
> On Wednesday, August 31st, 2022 at 09:50, Pekka Paalanen
> wrote:
>
> > > diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> > > index 86a292c3185a..cce1a1bea645 100644
> > > --- a/include/uapi/drm/drm_mode.h
> > > +++ b/include/uapi/drm/drm_mode.h
> > > @@ -942,6 +942,10 @@ struct hdr_output_metadata {
> > > * Request that the page-flip is performed as soon as possible, ie. with no
> > > * delay due to waiting for vblank. This may cause tearing to be visible on
> > > * the screen.
> > > + *
> > > + * When used with atomic uAPI, the driver will return an error if the
> > > hardware
> > > + * doesn't support performing an asynchronous page-flip for this update.
> > > + * User-space should handle this, e.g. by falling back to a regular
> > > page-flip.
> > > */
> > > #define DRM_MODE_PAGE_FLIP_ASYNC 0x02
> > > #define DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE 0x4
> >
> > Hi Simon,
> >
> > recalling what Ville explained that enabling async flips might require
> > one more sync flip first, how is that supposed to work?
> >
> > A TEST_ONLY commit is not allowed to change hardware state, and a
> > failing real commit is not allowed to change hardware state either
> > (right?), therefore a failing async flip cannot prepare the next flip
> > to be async, meaning async will never work.
>
> I'd blame it on bad hw, and make it one special quirk in the driver,
> just like it does now.
>
> Ville, thoughts?
I suppose it might be worth mentioning that special case here,
to avoid people getting confused why the first async flip was
accepted but took a full frame to complete.
--
Ville Syrjälä
Intel
