Hi Andrzej, On Mon, Mar 12, 2018 at 10:07:27AM +0100, Andrzej Hajda wrote: > 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. > I understand. The "transparent bridge" is of no actual use, but I don't see how the "double bridge" thing is not an issue if I were to develop support for the actual Thine chip. Please see my reply from yesterday to Archit. I still think having two bridges is somehow an issue... While we clarify that, would it be fine an initial driver version for the actualt Thine chip with a single input support[1]? I would ditch this transparent bridge and resume working on a THC63LVD1024 driver from comments received on v1. Thanks j [1] Single input support implies a single input port in DT bindings even if the chip supports two, and my understanding was that you didn't like this. > 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 > > > > > > > > >
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