Hi Andrej, On Thu, May 8, 2014 at 12:11 PM, Andrzej Hajda <a.hajda@xxxxxxxxxxx> wrote: > On 05/05/2014 09:52 PM, Ajay Kumar wrote: >> This patchset is based on exynos-drm-next-todo branch of Inki Dae's tree at: >> git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos.git >> >> I have just put up Rob's and Sean's idea of chaining up the bridges >> in code, and have implemented basic panel controls as a chained bridge. >> This works well with ptn3460 bridge chip on exynos5250-snow board. >> >> Still need to make use of standard list calls and figure out proper way >> of deleting the bridge chain. So, this is just a rough version. > > As I understand this patchset tries to solve two things: > 1. Implement panel as drm_bridge, to ease support for hardware chains: > Crtc -> Encoder -> Bridge -> Panel > 2. Add support to drm_bridge chaining, to allow software chains: > drm_crtc -> drm_encoder -> drm_bridge -> drm_bridge,panel > > It is done using Russian doll schema, ops from the bridge calls the same > ops from the next bridge and the next bridge ops can do the same. > > This schema means that all the bridges including the last one are seen > from the drm core point of view as a one big drm_bridge. Additionally in > this particular case, the first bridge (ptn3460) implements connector > so it is hard to guess what is the location of the 2nd bridge in video > stream chain, sometimes it is after the connector, sometimes before. > All this is quite confusing. > > But if you look at the bridge from upstream video interface point of > view it is just a panel, edp panel in case of ptn3460, ie ptn3460 on its > video input side acts as a panel. On the output side it expects a panel, > lvds panel in this case. > > So why not implement ptn3460 bridge as drm_panel which internally uses > another drm_panel. With this approach everything fits much better. > You do not need those (pre|post)_(enable|disable) calls, you do not need > to implement connector in the bridge and you have a driver following > linux driver model. And no single bit changed in drm core. This discussion should have ideally happened when Sean added bridge into drm-core! And, we do need (pre|post)_(enable|disable) calls for bridges, but the drm_panel framework supports only enable/disable. > I have implemented this way DSI/LVDS bridge, it was sent as RFC [1][2]. > It was not accepted as Inki preferred drm_bridge but as I see the > problems with drm_bridges I have decide to attract attention to much > more cleaner solution. > [1]: http://permalink.gmane.org/gmane.linux.drivers.devicetree/61559 > [2]: http://permalink.gmane.org/gmane.linux.kernel.samsung-soc/27044 > > Regards > Andrzej > > >> >> Ajay Kumar (3): >> [RFC V2 1/3] drm: implement chaining of drm bridges >> [RFC V2 2/3] drm/bridge: add a dummy panel driver to support lvds bridges >> [RFC V2 3/3] drm/bridge: ptn3460: support bridge chaining >> >> .../bindings/drm/bridge/bridge_panel.txt | 45 ++++ >> drivers/gpu/drm/bridge/Kconfig | 6 + >> drivers/gpu/drm/bridge/Makefile | 1 + >> drivers/gpu/drm/bridge/bridge_panel.c | 240 +++++++++++++++++++++ >> drivers/gpu/drm/bridge/ptn3460.c | 21 +- >> drivers/gpu/drm/drm_crtc.c | 13 +- >> include/drm/bridge/bridge_panel.h | 37 ++++ >> include/drm/drm_crtc.h | 2 + >> 8 files changed, 360 insertions(+), 5 deletions(-) >> create mode 100644 Documentation/devicetree/bindings/drm/bridge/bridge_panel.txt >> create mode 100644 drivers/gpu/drm/bridge/bridge_panel.c >> create mode 100644 include/drm/bridge/bridge_panel.h >> > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
