On Tue, May 11, 2021 at 10:19:09AM -0700, Stephen Boyd wrote: > Quoting Daniel Vetter (2021-05-11 06:39:36) > > On Tue, May 11, 2021 at 12:52 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > > > > > On Mon, May 10, 2021 at 9:08 PM Stephen Boyd <swboyd@xxxxxxxxxxxx> wrote: > > > > > > [cut] > > > > > > > > > > > > > > > > > > I will try it, but then I wonder about things like system wide > > > > > > suspend/resume too. The drm encoder chain would need to reimplement the > > > > > > logic for system wide suspend/resume so that any PM ops attached to the > > > > > > msm device run in the correct order. Right now the bridge PM ops will > > > > > > run, the i2c bus PM ops will run, and then the msm PM ops will run. > > > > > > After this change, the msm PM ops will run, the bridge PM ops will run, > > > > > > and then the i2c bus PM ops will run. It feels like that could be a > > > > > > problem if we're suspending the DSI encoder while the bridge is still > > > > > > active. > > > > > > > > > > Yup suspend/resume has the exact same problem as shutdown. > > > > > > > > I think suspend/resume has the exact opposite problem. At least I think > > > > the correct order is to suspend the bridge, then the encoder, i.e. DSI, > > > > like is happening today. It looks like drm_atomic_helper_shutdown() > > > > operates from the top down when we want bottom up? I admit I have no > > > > idea what is supposed to happen here. > > > > > > Why would the system-wide suspend ordering be different from the > > > shutdown ordering? > > > > At least my point was that both shutdown and suspend/resume have the > > same problem, and the righ fix is (I think at least) to add these > > hooks to the component.c aggregate ops structure. Hence just adding > > new callbacks for shutdown will be an incomplete solution. > > To add proper hooks to component.c we'll need to make the aggregate > device into a 'struct device' and make a bus for them that essentially > adds the aggregate device to the bus once all the components are > registered. The bind/unbind can be ported to probe/remove, and then the > aggregate driver can get PM ops that run before the component devices > run their PM ops. > > Let me go try it out and see if I can make it minimally invasive so that > the migration path is simple. Thanks for volunteeering. Please cc Greg KH so we make sure we're not doing this wrongly wrt the device model. -Daniel > > I don't feel like changing the global device order is the right > > approach, since essentially that's what component was meant to fix. > > Except it's incomplete since it only provides a solution for > > bind/unbind and not for shutdown or suspend/resume as other global > > state changes. I think some drivers "fixed" this by putting stuff like > > drm_atomic_helper_shutdown/suspend/resume into early/late hooks, to > > make sure that everything is ready with that trick. But that doesn't > > compose very well :-/ > > Yeah it looks like msm is using prepare/complete for this so that it can > jump in early and suspend the display pipeline before the components > suspend themselves. The shutdown path only has one callback so we can't > play the same games. Yeah there's tons of hacks. i915 component usage with audio has similar tricks to make suspend/resume work. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
