On Mon, May 20, 2019 at 08:41:09PM +0300, Imre Deak wrote:
> We allowed modesetting an unregistered connector only in the case the
> mode is getting disabled on the connector.
>
> The reason for this check was the lack of proper refcounting for the
> backing memory objects. That problem has been solved meanwhile so there
> is no reason any more to reject the modesetting in general. The check
> for that also makes driver internal modesets more cumbersome where we
> need to add exemptions for the cases where we do need to allow the
> modeset even for unregistered connectors. One such case is the
> restoration of the mode during resume.
>
> Simplify things by removing the unneeded check. I can't see how
> modesetting an unregistered connector can cause any problem and the race
> (described in the code comment) can anyway result in such a modeset (if
> the connector is unregistered right after the check).
>
> Cc: Lyude Paul <lyude@xxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
Lyude, could you test this change against the DDX fail scenario that the
check was added for originally (based on our IRC discussion)?
Thanks,
Imre
> ---
> drivers/gpu/drm/drm_atomic_helper.c | 29 ++---------------------------
> 1 file changed, 2 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 2e0cb4246cbd..e94e69483498 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -319,33 +319,6 @@ update_connector_routing(struct drm_atomic_state *state,
> return 0;
> }
>
> - crtc_state = drm_atomic_get_new_crtc_state(state,
> - new_connector_state->crtc);
> - /*
> - * For compatibility with legacy users, we want to make sure that
> - * we allow DPMS On->Off modesets on unregistered connectors. Modesets
> - * which would result in anything else must be considered invalid, to
> - * avoid turning on new displays on dead connectors.
> - *
> - * Since the connector can be unregistered at any point during an
> - * atomic check or commit, this is racy. But that's OK: all we care
> - * about is ensuring that userspace can't do anything but shut off the
> - * display on a connector that was destroyed after it's been notified,
> - * not before.
> - *
> - * Additionally, we also want to ignore connector registration when
> - * we're trying to restore an atomic state during system resume since
> - * there's a chance the connector may have been destroyed during the
> - * process, but it's better to ignore that then cause
> - * drm_atomic_helper_resume() to fail.
> - */
> - if (!state->duplicated && drm_connector_is_unregistered(connector) &&
> - crtc_state->active) {
> - DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] is not registered\n",
> - connector->base.id, connector->name);
> - return -EINVAL;
> - }
> -
> funcs = connector->helper_private;
>
> if (funcs->atomic_best_encoder)
> @@ -390,6 +363,8 @@ update_connector_routing(struct drm_atomic_state *state,
>
> set_best_encoder(state, new_connector_state, new_encoder);
>
> + crtc_state = drm_atomic_get_new_crtc_state(state,
> + new_connector_state->crtc);
> crtc_state->connectors_changed = true;
>
> DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] using [ENCODER:%d:%s] on [CRTC:%d:%s]\n",
> --
> 2.17.1
>
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