* [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET
@ 2020-06-03 10:45 Simon Ser
2020-06-03 11:06 ` Daniel Vetter
2020-06-03 11:13 ` Ville Syrjälä
0 siblings, 2 replies; 6+ messages in thread
From: Simon Ser @ 2020-06-03 10:45 UTC (permalink / raw)
To: dri-devel; +Cc: Manasi Navare
In update_output_state, the link-status property was reset to GOOD to
ensure legacy drmModeSetCrtc re-trains the link. However this auto-reset
is also performed on an atomic commit without ALLLOW_MODESET. If a
driver reads link-status to figure out whether to re-train the link,
this could cause an atomic commit failure. User-space doesn't expect
such a failure, because commits without ALLOW_MODESET aren't supposed to
fail because of link training issues.
Change update_output_state to implicitly reset link-status to GOOD only
if ALLOW_MODESET is set. This is the case for legacy drmModeSetCrtc
because drm_atomic_state_init sets it (and is used in
drm_atomic_helper_set_config, called from drm_mode_setcrtc).
Drivers don't seem to read link-status at the moment -- they seem to
rely on user-space performing a modeset instead. So this shouldn't
result in any change in behaviour, this should only prevent future
failures if drivers start reading link-status.
Signed-off-by: Simon Ser <contact@emersion.fr>
Suggested-by: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Manasi Navare <manasi.d.navare@intel.com>
---
drivers/gpu/drm/drm_atomic.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 965173fd0ac2..3d9d9e6f7397 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1426,7 +1426,8 @@ static int update_output_state(struct drm_atomic_state *state,
return ret;
/* Make sure legacy setCrtc always re-trains */
- new_conn_state->link_status = DRM_LINK_STATUS_GOOD;
+ if (state->allow_modeset)
+ new_conn_state->link_status = DRM_LINK_STATUS_GOOD;
}
}
--
2.26.2
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET
2020-06-03 10:45 [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET Simon Ser
@ 2020-06-03 11:06 ` Daniel Vetter
2020-06-03 11:13 ` Ville Syrjälä
1 sibling, 0 replies; 6+ messages in thread
From: Daniel Vetter @ 2020-06-03 11:06 UTC (permalink / raw)
To: Simon Ser; +Cc: Manasi Navare, dri-devel
On Wed, Jun 03, 2020 at 10:45:23AM +0000, Simon Ser wrote:
> In update_output_state, the link-status property was reset to GOOD to
> ensure legacy drmModeSetCrtc re-trains the link. However this auto-reset
> is also performed on an atomic commit without ALLLOW_MODESET. If a
> driver reads link-status to figure out whether to re-train the link,
> this could cause an atomic commit failure. User-space doesn't expect
> such a failure, because commits without ALLOW_MODESET aren't supposed to
> fail because of link training issues.
>
> Change update_output_state to implicitly reset link-status to GOOD only
> if ALLOW_MODESET is set. This is the case for legacy drmModeSetCrtc
> because drm_atomic_state_init sets it (and is used in
> drm_atomic_helper_set_config, called from drm_mode_setcrtc).
>
> Drivers don't seem to read link-status at the moment -- they seem to
> rely on user-space performing a modeset instead. So this shouldn't
> result in any change in behaviour, this should only prevent future
> failures if drivers start reading link-status.
>
> Signed-off-by: Simon Ser <contact@emersion.fr>
> Suggested-by: Pekka Paalanen <ppaalanen@gmail.com>
I think we should have Cc: stable@vger.kernel.org on this. Also I think
would be really awesome if we can update/extend the igt, but I guess if
you don't have a chamelium it's a bit hard to make that happen :-/
Also I guess you'll reflect this in your doc patch?
With the cc: stable this has my Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cheers, Daniel
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> ---
> drivers/gpu/drm/drm_atomic.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 965173fd0ac2..3d9d9e6f7397 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1426,7 +1426,8 @@ static int update_output_state(struct drm_atomic_state *state,
> return ret;
>
> /* Make sure legacy setCrtc always re-trains */
> - new_conn_state->link_status = DRM_LINK_STATUS_GOOD;
> + if (state->allow_modeset)
> + new_conn_state->link_status = DRM_LINK_STATUS_GOOD;
> }
> }
>
> --
> 2.26.2
>
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET
2020-06-03 10:45 [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET Simon Ser
2020-06-03 11:06 ` Daniel Vetter
@ 2020-06-03 11:13 ` Ville Syrjälä
2020-06-03 11:36 ` Daniel Vetter
1 sibling, 1 reply; 6+ messages in thread
From: Ville Syrjälä @ 2020-06-03 11:13 UTC (permalink / raw)
To: Simon Ser; +Cc: Manasi Navare, dri-devel
On Wed, Jun 03, 2020 at 10:45:23AM +0000, Simon Ser wrote:
> In update_output_state, the link-status property was reset to GOOD to
> ensure legacy drmModeSetCrtc re-trains the link. However this auto-reset
> is also performed on an atomic commit without ALLLOW_MODESET. If a
I didn't think udate_output_state() was getting called for
non-legacy paths. Where is that coming from?
> driver reads link-status to figure out whether to re-train the link,
> this could cause an atomic commit failure. User-space doesn't expect
> such a failure, because commits without ALLOW_MODESET aren't supposed to
> fail because of link training issues.
>
> Change update_output_state to implicitly reset link-status to GOOD only
> if ALLOW_MODESET is set. This is the case for legacy drmModeSetCrtc
> because drm_atomic_state_init sets it (and is used in
> drm_atomic_helper_set_config, called from drm_mode_setcrtc).
>
> Drivers don't seem to read link-status at the moment -- they seem to
> rely on user-space performing a modeset instead. So this shouldn't
> result in any change in behaviour, this should only prevent future
> failures if drivers start reading link-status.
>
> Signed-off-by: Simon Ser <contact@emersion.fr>
> Suggested-by: Pekka Paalanen <ppaalanen@gmail.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> ---
> drivers/gpu/drm/drm_atomic.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 965173fd0ac2..3d9d9e6f7397 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1426,7 +1426,8 @@ static int update_output_state(struct drm_atomic_state *state,
> return ret;
>
> /* Make sure legacy setCrtc always re-trains */
> - new_conn_state->link_status = DRM_LINK_STATUS_GOOD;
> + if (state->allow_modeset)
> + new_conn_state->link_status = DRM_LINK_STATUS_GOOD;
> }
> }
>
> --
> 2.26.2
>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Ville Syrjälä
Intel
_______________________________________________
dri-devel mailing list
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https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET
2020-06-03 11:13 ` Ville Syrjälä
@ 2020-06-03 11:36 ` Daniel Vetter
2020-06-03 13:17 ` Simon Ser
0 siblings, 1 reply; 6+ messages in thread
From: Daniel Vetter @ 2020-06-03 11:36 UTC (permalink / raw)
To: Ville Syrjälä; +Cc: Manasi Navare, dri-devel
On Wed, Jun 03, 2020 at 02:13:43PM +0300, Ville Syrjälä wrote:
> On Wed, Jun 03, 2020 at 10:45:23AM +0000, Simon Ser wrote:
> > In update_output_state, the link-status property was reset to GOOD to
> > ensure legacy drmModeSetCrtc re-trains the link. However this auto-reset
> > is also performed on an atomic commit without ALLLOW_MODESET. If a
>
> I didn't think udate_output_state() was getting called for
> non-legacy paths. Where is that coming from?
Oops, I'm blind and you're right, there's no bug. We already only
force-set this for legacy modeset (and fbcon).
That also means that atomic userspace has to handle this, which is maybe
not so awesome ... So maybe we need to duct-tape over this for atomic too,
and in that case it should be only done when ALLOW_MODESET is set.
But maybe all the compositors that care will handle this :-/
-Daniel
>
> > driver reads link-status to figure out whether to re-train the link,
> > this could cause an atomic commit failure. User-space doesn't expect
> > such a failure, because commits without ALLOW_MODESET aren't supposed to
> > fail because of link training issues.
> >
> > Change update_output_state to implicitly reset link-status to GOOD only
> > if ALLOW_MODESET is set. This is the case for legacy drmModeSetCrtc
> > because drm_atomic_state_init sets it (and is used in
> > drm_atomic_helper_set_config, called from drm_mode_setcrtc).
> >
> > Drivers don't seem to read link-status at the moment -- they seem to
> > rely on user-space performing a modeset instead. So this shouldn't
> > result in any change in behaviour, this should only prevent future
> > failures if drivers start reading link-status.
> >
> > Signed-off-by: Simon Ser <contact@emersion.fr>
> > Suggested-by: Pekka Paalanen <ppaalanen@gmail.com>
> > Cc: Daniel Vetter <daniel@ffwll.ch>
> > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> > drivers/gpu/drm/drm_atomic.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 965173fd0ac2..3d9d9e6f7397 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1426,7 +1426,8 @@ static int update_output_state(struct drm_atomic_state *state,
> > return ret;
> >
> > /* Make sure legacy setCrtc always re-trains */
> > - new_conn_state->link_status = DRM_LINK_STATUS_GOOD;
> > + if (state->allow_modeset)
> > + new_conn_state->link_status = DRM_LINK_STATUS_GOOD;
> > }
> > }
> >
> > --
> > 2.26.2
> >
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
> --
> Ville Syrjälä
> Intel
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET
2020-06-03 11:36 ` Daniel Vetter
@ 2020-06-03 13:17 ` Simon Ser
2020-06-03 13:45 ` Daniel Vetter
0 siblings, 1 reply; 6+ messages in thread
From: Simon Ser @ 2020-06-03 13:17 UTC (permalink / raw)
To: Daniel Vetter; +Cc: Manasi Navare, dri-devel@lists.freedesktop.org
On Wednesday, June 3, 2020 1:36 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Wed, Jun 03, 2020 at 02:13:43PM +0300, Ville Syrjälä wrote:
>
> > On Wed, Jun 03, 2020 at 10:45:23AM +0000, Simon Ser wrote:
> >
> > > In update_output_state, the link-status property was reset to GOOD to
> > > ensure legacy drmModeSetCrtc re-trains the link. However this auto-reset
> > > is also performed on an atomic commit without ALLLOW_MODESET. If a
> >
> > I didn't think udate_output_state() was getting called for
> > non-legacy paths. Where is that coming from?
>
> Oops, I'm blind and you're right, there's no bug. We already only
> force-set this for legacy modeset (and fbcon).
Indeed, good catch Ville. set_config is purely a legacy thing.
> That also means that atomic userspace has to handle this, which is maybe
> not so awesome ... So maybe we need to duct-tape over this for atomic too,
> and in that case it should be only done when ALLOW_MODESET is set.
>
> But maybe all the compositors that care will handle this :-/
Not fond of this because we'll basically end up with some drivers
checking for link-status (none do that yet) and some user-space
resetting it to GOOD. It'll break only if user-space doesn't reset and
a driver which checks link-status is used. Driver-specific behaviour
isn't great.
_______________________________________________
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https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET
2020-06-03 13:17 ` Simon Ser
@ 2020-06-03 13:45 ` Daniel Vetter
0 siblings, 0 replies; 6+ messages in thread
From: Daniel Vetter @ 2020-06-03 13:45 UTC (permalink / raw)
To: Simon Ser; +Cc: Manasi Navare, dri-devel@lists.freedesktop.org
On Wed, Jun 03, 2020 at 01:17:14PM +0000, Simon Ser wrote:
> On Wednesday, June 3, 2020 1:36 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
>
> > On Wed, Jun 03, 2020 at 02:13:43PM +0300, Ville Syrjälä wrote:
> >
> > > On Wed, Jun 03, 2020 at 10:45:23AM +0000, Simon Ser wrote:
> > >
> > > > In update_output_state, the link-status property was reset to GOOD to
> > > > ensure legacy drmModeSetCrtc re-trains the link. However this auto-reset
> > > > is also performed on an atomic commit without ALLLOW_MODESET. If a
> > >
> > > I didn't think udate_output_state() was getting called for
> > > non-legacy paths. Where is that coming from?
> >
> > Oops, I'm blind and you're right, there's no bug. We already only
> > force-set this for legacy modeset (and fbcon).
>
> Indeed, good catch Ville. set_config is purely a legacy thing.
>
> > That also means that atomic userspace has to handle this, which is maybe
> > not so awesome ... So maybe we need to duct-tape over this for atomic too,
> > and in that case it should be only done when ALLOW_MODESET is set.
> >
> > But maybe all the compositors that care will handle this :-/
>
> Not fond of this because we'll basically end up with some drivers
> checking for link-status (none do that yet) and some user-space
> resetting it to GOOD. It'll break only if user-space doesn't reset and
> a driver which checks link-status is used. Driver-specific behaviour
> isn't great.
See my other reply, drivers don't need to check for GOOD, it's kinda
magic.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-06-03 13:45 UTC | newest]
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2020-06-03 10:45 [PATCH] drm/atomic: don't reset link-status to GOOD without ALLOW_MODESET Simon Ser
2020-06-03 11:06 ` Daniel Vetter
2020-06-03 11:13 ` Ville Syrjälä
2020-06-03 11:36 ` Daniel Vetter
2020-06-03 13:17 ` Simon Ser
2020-06-03 13:45 ` Daniel Vetter
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