On Wed, Jun 03, 2020 at 01:27:55PM +0000, Simon Ser wrote: > > > + * When user-space performs an atomic commit on a connector with a "BAD" > > > + * link-status without resetting the property to "GOOD", it gets > > > + * implicitly reset. This might make the atomic commit fail if the modeset > > > + * is unsuccessful. > > > > I think this was what Daniel was saying that the kernel should require > > ALLOW_MODESET to be set for the automatic reset, right? > > Actually this paragraph isn't true. link-status is only reset to GOOD for > legacy modeset. > > But right now this doesn't matter since no driver reads the link-status > property value as far as I can tell. Note, only i915 sets link-status > to BAD. It's magic ... change in link status results in connectors_change (or something like that), which forces the modeset (and first recomputation of mode state) that fixes everything up. But yeah I entirely missed that the autoreset to GOOD only happens in legacy modeset. I guess we might have some atomic compositors with slightly suboptimal handling of link status failure :-/ > > I'm fine with how the doc is written now. But if ALLOW_MODESET becomes > > a requirement for the automatic reset, I suspect there is a risk to > > regress Weston, assuming the automatic reset used to be successful. > > Right now a commit without ALLOW_MODESET won't reset link-status to GOOD, > but also won't re-train the link on i915. So I think it's fine to require > ALLOW_MODESET. > > Should drivers read the value of the link-status property? Or should we > ignore user-space writes to the property and only require ALLOW_MODESET > to re-train the link? Well without allow_modeset it'll fail, that's the problem. But since we dont automatically restore, I think the only problem is that existing atomic userspace might be stuck on a bad link for a while ... -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
