On Wed, 5 Jul 2023 at 17:24, Maxime Ripard <mripard@xxxxxxxxxx> wrote: > > On Wed, Jul 05, 2023 at 04:37:57PM +0300, Dmitry Baryshkov wrote: > > > > > > > > > > Either way, I'm not really sure it's a good idea to multiply the > > > > > capabilities flags of the DSI host, and we should just stick to the > > > > > spec. If the spec says that we have to support DSC while video is > > > > > output, then that's what the panels should expect. > > > > > > > > Except some panels supports DSC & non-DSC, Video and Command mode, and > > > > all that is runtime configurable. How do you handle that ? > > > > > > In this case, most of the constraints are going to be on the encoder > > > still so it should be the one driving it. The panel will only care about > > > which mode has been selected, but it shouldn't be the one driving it, > > > and thus we still don't really need to expose the host capabilities. > > > > This is an interesting perspective. This means that we can and actually have > > to extend the drm_display_mode with the DSI data and compression > > information. > > I wouldn't extend drm_display_mode, but extending one of the state > structures definitely. > > We already have some extra variables in drm_connector_state for HDMI, > I don't think it would be a big deal to add a few for MIPI-DSI. > > We also floated the idea for a while to create bus-specific states, with > helpers to match. Maybe it would be a good occasion to start doing it? > > > For example, the panel that supports all four types for the 1080p should > > export several modes: > > > > 1920x1080-command > > 1920x1080-command-DSC > > 1920x1080-video > > 1920x1080-video-DSC > > > > where video/command and DSC are some kinds of flags and/or information in > > the drm_display_mode? Ideally DSC also has several sub-flags, which denote > > what kind of configuration is supported by the DSC sink (e.g. bpp, yuv, > > etc). > > So we have two things to do, right? We need to expose what the panel can > take (ie, EDID for HDMI), and then we need to tell it what we picked > (infoframes). > > We already express the former in mipi_dsi_device, so we could extend the > flags stored there. > > And then, we need to tie what the DSI host chose to a given atomic state > so the panel knows what was picked and how it should set everything up. This is definitely something we need. Marijn has been stuck with the panels that support different models ([1]). Would you prefer a separate API for this kind of information or abusing atomic_enable() is fine from your point of view? My vote would be for going with existing operations, with the slight fear of ending up with another DSI-specific hack (like pre_enable_prev_first). > > > Another option would be to get this handled via the bus format negotiation, > > but that sounds like worse idea to me. > > Yeah, I'm not really fond of the format negociation stuff either. [1] https://lore.kernel.org/linux-arm-msm/20230521-drm-panels-sony-v1-8-541c341d6bee@xxxxxxxxxxxxxx/ -- With best wishes Dmitry
