On Wed, Jun 12, 2024 at 07:39:01AM -0700, Doug Anderson wrote: > Hi, > > On Wed, Jun 12, 2024 at 1:09 AM Maxime Ripard <mripard@xxxxxxxxxx> wrote: > > > > Hi, > > > > On Tue, Jun 11, 2024 at 07:48:51AM GMT, Douglas Anderson wrote: > > > At shutdown if you've got a _properly_ coded DRM modeset driver then > > > you'll get these two warnings at shutdown time: > > > > > > Skipping disable of already disabled panel > > > Skipping unprepare of already unprepared panel > > > > > > These warnings are ugly and sound concerning, but they're actually a > > > sign of a properly working system. That's not great. > > > > > > It's not easy to get rid of these warnings. Until we know that all DRM > > > modeset drivers used with panel-simple and panel-edp are properly > > > calling drm_atomic_helper_shutdown() or drm_helper_force_disable_all() > > > then the panel drivers _need_ to disable/unprepare themselves in order > > > to power off the panel cleanly. However, there are lots of DRM modeset > > > drivers used with panel-edp and panel-simple and it's hard to know > > > when we've got them all. Since the warning happens only on the drivers > > > that _are_ updated there's nothing to encourage broken DRM modeset > > > drivers to get fixed. > > > > > > In order to flip the warning to the proper place, we need to know > > > which modeset drivers are going to shutdown properly. Though ugly, do > > > this by creating a list of everyone that shuts down properly. This > > > allows us to generate a warning for the correct case and also lets us > > > get rid of the warning for drivers that are shutting down properly. > > > > > > Maintaining this list is ugly, but the idea is that it's only short > > > term. Once everyone is converted we can delete the list and call it > > > done. The list is ugly enough and adding to it is annoying enough that > > > people should push to make this happen. > > > > > > Implement this all in a shared "header" file included by the two panel > > > drivers that need it. This avoids us adding an new exports while still > > > allowing the panel drivers to be modules. The code waste should be > > > small and, as per above, the whole solution is temporary. > > > > > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > > > --- > > > I came up with this idea to help us move forward since otherwise I > > > couldn't see how we were ever going to fix panel-simple and panel-edp > > > since they're used by so many DRM Modeset drivers. It's a bit ugly but > > > I don't hate it. What do others think? > > > > I don't think it's the right approach, even more so since we're so close > > now to having it in every driver. > > > > I ran the coccinelle script we started with, and here are the results: > > > > ./drivers/gpu/drm/vmwgfx/vmwgfx_drv.c:1640:25-39: ERROR: KMS driver vmw_pci_driver is missing shutdown implementation > > ./drivers/gpu/drm/kmb/kmb_drv.c:621:30-49: ERROR: KMS driver kmb_platform_driver is missing shutdown implementation > > ./drivers/gpu/drm/tiny/arcpgu.c:422:30-52: ERROR: KMS driver arcpgu_platform_driver is missing shutdown implementation > > Sure, although I think we agreed even back when we talked about this > last that your coccinelle script wasn't guaranteed to catch every > driver. ...so I guess the question is: are we willing to accept that > we'll stop disabling panels at shutdown for any drivers that might > were missed. For instance, looking at it by hand (which also could > miss things), I previously thought that we also might need: > > * nouveau > * tegra > * amdgpu > * sprd > * gma500 > * radeon > > I sent patches for those drivers but they don't go through drm-misc > and some of the drivers had a lot of abstraction layers and were hard > to reason about. I'm also not 100% confident that all of those drivers > really are affected--they'd have to be used with panel-simple or > panel-edp... Aside from amdgpu and radeon they're all in -misc now, and Alex is generally fairly responsive. > In any case, having some sort of warning that would give us a > definitive answer would be nice. My proposed patch would give us that > warning. I could even jump to a WARN_ON right from the start. Yeah we defo want some warning to at least check this at runtime. > My proposed patch is self-admittedly super ugly and is also designed > to be temporary, so I don't think of this as giving up right before > crossing the finish line but instead accepting a tiny bit of temporary > ugliness to make sure that we don't accidentally regress anyone. I > would really hope it would be obvious to anyone writing / reviewing > drivers that the function I introduced isn't intended for anyone but > panel-simple and panel-edp. See my other reply for the proper design fix, and my apologies for what you stepped into here :-/ -Sima -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
