[PATCH v3 6/6] drm/ingenic: Attach bridge chain to encoders

[H. Nikolaus Schaller]

Hi Paul,

> Am 23.09.2021 um 22:23 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> 
>> Because your "it doesn't work" arguments have zero weight otherwise.
> 
> I hope I still can find it. So I can't promise anything.
> We have had it complete in DTS and added code to parse it.
> It may have been wiped out by cleaning up patch series during rebase.

I was able to locate it and place it on top of your ingenic-drm-drv v3
and our synopsys hdmi v3 [1] (+ unpublished work).

This [2] should save you a lot of time making dw-hdmi work on jz4780 at all, so you can
focus on our mistakes instead of starting from scratch.

Features:
- based on v5.15-rc2
- (the first two patches are LetuxOS and build system related and can be ignored for this discussion)
- contains some significant patch from drm-next not yet upstream
- contains your v3 series as is
- (initially) disables your DRM_BRIDGE_ATTACH_NO_CONNECTOR (is reverted in the last patch)
- adds synopsys stuff and DT schema
- adds jz4780.dtsi and ci20.dts
- adds ci20_defconfig
- (adds some (optional) jz4780 specific features we likely do not need now)
- adds something to dw-hdmi to properly notify HPD
- adds a hdmi-regulator so that HPD power can be turned on/off
- (attempt to configure the dw-hdmi unwedge feature)
- then we add the hdmi-connector to replace the dw-hdmi connector to device tree
- and finally re-enable DRM_BRIDGE_ATTACH_NO_CONNECTOR

The result is
a) without the last patch I get a proper setup with framebuffer and edid.
Unfortunateley without any image on HDMI.

b) if last patch is included
(so that DRM_BRIDGE_ATTACH_NO_CONNECTOR is required as by your [patch v3 6/6] again)
I get:

[    4.351200] [drm:drm_bridge_attach [drm]] *ERROR* failed to attach bridge /hdmi at 10180000 to encoder DPI-34: -22
[    4.474346] [drm:drm_bridge_attach [drm]] *ERROR* failed to attach bridge (null) to encoder DPI-34: -22
[    4.562125] ingenic-drm 13050000.lcdc0: Unable to attach bridge
[    4.568103] ingenic-drm: probe of 13050000.lcdc0 failed with error -22

Maybe you can spot the bug in the code much quicker than we can.

I do not know what Paul Boddie did differently if this initialization
with connector-hdmi works for him and does not fail likewise.

BR and thanks,
Nikolaus


[1]: https://lore.kernel.org/linux-mips/8e873f17fcc9aeb326d99b7c2c8cd25b61dca6f5.1628399442.git.hns@goldelico.com/T/
[2]: https://git.goldelico.com/?p=letux-kernel.git;a=shortlog;h=refs/heads/upstream%2Bjz4780%2Bhdmi-connector