Hi Paul,
Am 23.09.2021 um 10:49 schrieb Paul Cercueil paul@crapouillou.net:
Hi Nikolaus,
Le jeu., sept. 23 2021 at 07:52:08 +0200, H. Nikolaus Schaller hns@goldelico.com a écrit :
Hi Paul, thanks for another update. We have been delayed to rework the CI20 HDMI code on top of your series but it basically works in some situations. There is for example a problem if the EDID reports DRM_COLOR_FORMAT_YCRCB422 but it appears to be outside of your series.
I think the SoC can output YCbCr as well, but I never tried to use it.
Maybe there is code missing or something else. We have not yet deeply researched. Except that when ignoring DRM_COLOR_FORMAT_YCRCB422 capability it uses RGB and works.
ret = drm_bridge_attach(encoder, &ib->bridge, NULL,DRM_BRIDGE_ATTACH_NO_CONNECTOR);DRM_BRIDGE_ATTACH_NO_CONNECTOR makes it fundamentally incompatible with synopsys/dw_hdmi.c That driver checks for DRM_BRIDGE_ATTACH_NO_CONNECTOR being NOT present, since it wants to register its own connector through dw_hdmi_connector_create(). It does it for a reason: the dw-hdmi is a multi-function driver which does HDMI and DDC/EDID stuff in a single driver (because I/O registers and power management seem to be shared).
The IT66121 driver does all of that too, and does not need DRM_BRIDGE_ATTACH_NO_CONNECTOR. The drm_bridge_funcs struct has callbacks to handle cable detection and DDC stuff.
Since I do not see who could split this into a separate bridge and a connector driver and test it on multiple SoC platforms (there are at least 3 or 4), I think modifying the fundamentals of the dw-hdmi architecture just to get CI20 HDMI working is not our turf.
You could have a field in the dw-hdmi pdata structure, that would instruct the driver whether or not it should use the new API. Ugly, I know, and would probably duplicate a lot of code, but that would allow other drivers to be updated at a later date.
Yes, would be very ugly.
But generally who has the knowledge (and time) to do this work? And has a working platform to test (jz4780 isn't a good development environment)?
The driver seems to have a turbulent history starting 2013 in staging/imx and apparently it was generalized since then... Is Laurent currently dw-hdmi maintainer?
Therefore the code here should be able to detect if drm_bridge_attach() already creates and attaches a connector and then skip the code below.
Not that easy, unfortunately. On one side we have dw-hdmi which checks that DRM_BRIDGE_ATTACH_NO_CONNECTOR is not set, and on the other side we have other drivers like the IT66121 which will fail if this flag is not set.
Ok, I see. You have to handle contradicting cases here.
Would it be possible to run it with DRM_BRIDGE_ATTACH_NO_CONNECTOR first and retry if it fails without?
But IMHO the return value (in error case) is not well defined. So there must be a test if a connector has been created (I do not know how this would work).
Another suggestion: can you check if there is a downstream connector defined in device tree (dw-hdmi does not need such a definition)? If not we call it with 0 and if there is one we call it with DRM_BRIDGE_ATTACH_NO_CONNECTOR and create one?
Just some ideas how to solve without touching hdmi drivers.
BR and thanks, Nikolaus