Hi Alexander,
On 2022-01-16 11:14, Alexander Stein wrote:
> Hi Stefan,
>
> Am Samstag, 15. Januar 2022, 14:28:01 CET schrieb Stefan Agner:
>> That assumption turned out to be wrong: I used our mainline based U-Boot
>> 2021.10 instead of the Arch Linux ARM U-Boot, and HDMI CEC continued to
>> work.
>
> Does the mainstream U-Boot work out of the box? Or does it require some
> additional configuration?
>
Yes mainline U-Boot works out of the box. Building it is somewhat
involved since it requires extra firmwares (there are build instructions
in the source tree in board/amlogic/w400/README.odroid-n2).
You need to add a boot script to your boot partition. I used the script
part of the uboot-odroid-n2-mainline package as inspiration [1]. It
needs some adjustments as it seems to try to boot from the root file
system directly (and my setup used the FAT/ext4 setup still).
We carry a single patch which improved reliability booting from eMMC,
see [2].
>> I then moved to 5.15.13 as well to rule out any kernel changes. But
>> still, in our configuration HDMI CEC did not work. I ended up diffing
>> configuration, and noticed that we are using built-in CONFIG_CEC_CORE
>> whereas Arch Linux uses it as a module. To build CONFIG_CEC_CORE as a
>> module I had to change some other configuration from built-in to module,
>> namely:
>>
>> - CONFIG_CEC_CORE=m
>> - CONFIG_DRM_DW_HDMI=m
>> - CONFIG_DRM_MESON=m
>> - CONFIG_DRM_MESON_DW_HDMI=m
>>
>> With that change, HDMI CEC started to work in my builds too!
>>
>> With that change, it also works on Linux 5.10.
>>
>> I guess there is some ordering issue or something which makes it fail
>> when those drivers are built-in? Note that I did not change
>> CONFIG_CEC_MESON_G12A_AO, that driver was already a module before.
>
> You need all 4 options above to be modules? Or is it maybe enough to set
> CONFIG_DRM_DW_HDMI_CEC=m? This should make CONFIG_CEC_CORE=m as well, while
> the other modules are built-in.
In our builds I disabled CONFIG_DRM_DW_HDMI_CEC entirely actually.
It seems that CONFIG_DRM_DW_HDMI is tied to CEC_CORE through this
dependency:
config DRM_DW_HDMI
...
select CEC_CORE if CEC_NOTIFIER
> I suspect at some point a -EPROBE_DEFER is missing.
>
> Just FYI: Arch Linux aarch64 kernel config currently lacks some drivers for
> HDMI audio. See [1].
Thanks for the link, just checked, it seems our kernel configuration
covers those.
--
Stefan
>
> Best regards,
> Alexander
>
> [1] https://github.com/archlinuxarm/PKGBUILDs/pull/1864
[1]
https://github.com/archlinuxarm/PKGBUILDs/blob/master/alarm/uboot-odroid-c2-mainline/boot.txt
[2]
https://github.com/home-assistant/operating-system/blob/rel-7/buildroot-external/board/hardkernel/patches/uboot/0001-HACK-mmc-meson-gx-limit-to-24MHz.patch
