On 09.03.2018 14:51, Jacopo Mondi wrote: > Hello, > after some discussion on the proposed bindings for generic lvds decoder and > Thine THC63LVD1024, I decided to drop the THC63 specific part and just live with > a transparent decoder that does not support any configuration from DT. > > Dropping THC63 support to avoid discussion on how to better implement support > for a DRM bridge with 2 input ports and focus on LVDS mode propagation through > bridges as explained in v1 cover letter (for DRM people: please see [1] as why > I find difficult to implement support for bridges with multiple input endpoints) > > Same base branch as v1, with same patches for V3M Eagle applied on top. > git://jmondi.org/linux v3m/v4.16-rc3/base > > Thanks > j > > v1 -> v2: > - Drop support for THC63LVD1024 > > [1] I had a quick at how to model a DRM bridge with multiple input > ports, and I see a blocker in how DRM identifies and matches bridges using > the devices node in place of the endpoint nodes. > > As THC63LVD1024 supports up to 2 LVDS inputs and 2 LVDS outputs, I see only > a few ways to support that: > 1) register 2 drm bridges from the same driver (one for each input/output pair) > but they would both be matches on the same device node when the preceding > bridge calls "of_drm_find_bridge()". > 2) register a single bridge with multiple "next bridges", but when the bridge > gets attached I don't see a way on how to identify on which next bridge > "drm_bridge_attach()" on, as it depends on the endpoint the current bridge > has been attached on first, and we don't have that information. > 3) Register more instances of the same chip in DTS, one for each input/output > pair. They gonna share supplies and gpios, and I don't like that. > > I had a quick look at the currently in mainline bridges and none of them has > multiple input endpoints, except for HDMI audio endpoint, which I haven't found > in use in any DTS. I guess the problem has been already debated and maybe solved > in the past, so feel free to point me to other sources. I think this is is a step in wrong direction, IMHO. Your previous patchset was quite OK, at least bindings, IMHO. Few things needed only polishing. Here we have unmanaged/transparent bridge, which is totally different, what happened to regulators and gpios from previous iteration. I do not have schematics of the board, but I guess respective pins of the bridge must be connected somehow. I think the problem you want to avoid (double bridge) should not be a problem at all. I suppose the most important is to have correct bindings - as they need to be stable. If you really must to do hacks better is to put them into driver. Regards Andrzej > > Jacopo Mondi (3): > dt-bindings: display: bridge: Document LVDS to parallel decoder > drm: bridge: Add LVDS decoder driver > arm64: dts: renesas: Add LVDS decoder to R-Car V3M Eagle > > .../bindings/display/bridge/lvds-decoder.txt | 42 ++++++ > arch/arm64/boot/dts/renesas/r8a77970-eagle.dts | 31 +++- > drivers/gpu/drm/bridge/Kconfig | 8 ++ > drivers/gpu/drm/bridge/Makefile | 1 + > drivers/gpu/drm/bridge/lvds-decoder.c | 157 +++++++++++++++++++++ > 5 files changed, 237 insertions(+), 2 deletions(-) > create mode 100644 Documentation/devicetree/bindings/display/bridge/lvds-decoder.txt > create mode 100644 drivers/gpu/drm/bridge/lvds-decoder.c > > -- > 2.7.4 > > > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
