kernel module that supports usb-c hdmi

[alexandre]

Hi, I currently run a 5.7 kernel on my pinebookpro that supports my usb-c hub, especially its HDMI output. I got it installing archlinuxarm from a repo that was called «simulated-earth» or something like this (thanks to those guys if they ever read me ). But as this repo is dead for a while now, i'm still using this pretty old kernel. I've tried the one provided by Nadia, which is very up-to-date, but cant, unfortunately, make my HDMI output works. I assume this is du to a specific kernel module, but as I am far from being an expert I can just show you the return of lsmod, and ask you for your help if you can identify if there really is an exotic module that should be responsible for this well behavior of this kernel :

rpcsec_gss_krb5        36864  0
snd_usb_audio        266240  2
snd_usbmidi_lib        40960  1 snd_usb_audio
snd_hwdep              20480  1 snd_usb_audio
snd_rawmidi            45056  1 snd_usbmidi_lib
snd_seq_device        20480  1 snd_rawmidi
snd_soc_hdmi_codec    16384  0
cdc_ether              20480  0
usbnet                49152  1 cdc_ether
r8152                  86016  0
mii                    20480  2 usbnet,r8152
snd_soc_simple_amplifier    16384  1
panfrost              65536  0
gpu_sched              32768  1 panfrost
hci_uart              118784  0
btqca                  16384  1 hci_uart
btbcm                  24576  1 hci_uart
btintel                32768  1 hci_uart
joydev                32768  0
bluetooth            454656  5 btqca,btintel,hci_uart,btbcm
snd_soc_rockchip_i2s    16384  2
snd_soc_rockchip_pcm    16384  1 snd_soc_rockchip_i2s
rockchip_rga          28672  0
dw_wdt                20480  0
videobuf2_dma_sg      24576  1 rockchip_rga
cw2015_battery        16384  0
ecdh_generic          16384  1 bluetooth
ecc                    32768  1 ecdh_generic
rfkill                40960  2 bluetooth
hantro_vpu            90112  0
snd_soc_es8316        40960  1
rockchipdrm          147456  2
dw_mipi_dsi            20480  1 rockchipdrm
dw_hdmi                53248  1 rockchipdrm
analogix_dp            45056  1 rockchipdrm
cec                    61440  1 dw_hdmi
rockchip_saradc        16384  0
rc_core                57344  1 cec
drm_kms_helper        241664  4 dw_mipi_dsi,rockchipdrm,dw_hdmi,analogix_dp
rockchip_thermal      24576  0
syscopyarea            16384  1 drm_kms_helper
sysfillrect            16384  1 drm_kms_helper
sysimgblt              16384  1 drm_kms_helper
fb_sys_fops            16384  1 drm_kms_helper
snd_soc_simple_card    20480  1
snd_soc_simple_card_utils    24576  1 snd_soc_simple_card
panel_simple          81920  0
pwm_bl                16384  0
drm                  622592  10 gpu_sched,drm_kms_helper,dw_mipi_dsi,panel_simple,rockchipdrm,dw_hdmi,panfrost,analogix_dp
drm_panel_orientation_quirks    20480  1 drm
gpio_keys              24576  0
hid_multitouch        32768  0


Thanks for any suggestions,
alex

[tophneal]

IIRC the linux-pinebookpro kernel in the Manjaro repos should enable this support.
https://forum.manjaro.org/t/dp-alt-mode-...y-pbp/8036

[Arwen]

Also, for others reading this, the Pinebook Pro does not support USB C alternate mode, HDMI video.

Our Pinebook Pros DO support USB C alternate mode DisplayPort video. This DisplayPort video output CAN be turned into HDMI in the USB dock or adapter using active electronics.

The reason I want this clear, is that their may be a difference in kernel modules for USB C alternate modes. So for the Pinebook Pro, always select DisplayPort. Even if your dock / adapter has HDMI connector(s).

[alexandre]

I think i didnt understand : do you say i should have to do something in order for my hub to be able to use the hdmi video output ? I have to say, that currently, with the kernel i run, i have nothing to do : it just works perfectly (i can have both displays, the laptop one and an hdmi monitor, in mirror mode, or duplicate, and the simple xfce applet for managing displays is very responsive…) as soon as i plug the hub (one of this cheap hub one can buy on amazon).

I did a diff with the lsmod outputs according to which kernel i run. The only difference between them that involve hdmi is some snd_soc_hdmi_codec that is present in the 5.7 not in the 5.10 but it sounds like it has something do to with audio, not video…

[Arwen]

@alexandre As long as your hardware has worked once with your Pinebook Pro, then it's the right type. Sounds like it uses an internal convertor from DisplayPort to HDMI.

I can't really help you with the software aspect...


The USB C standard is one of the most bizarre and complicated things in existence. It & the connector tries to be everything to everyone, even when their are competing / conflicting standards. Like the alternate mode video options. First released was DisplayPort, so that is what many USB C alternate video mode devices use. Later came the USB C alternate mode HDMI video, which is NOT compatible with our Pinebook Pros.

As I said, it's complicated.

[alexandre]

@alexandre  As long as your hardware has worked once with your Pinebook Pro, then it's the right type. Sounds like it uses an internal convertor from DisplayPort to HDMI.

I can't really help you with the software aspect...


The USB C standard is one of the most bizarre and complicated things in existence. It & the connector tries to be everything to everyone, even when their are competing / conflicting standards. Like the alternate mode video options. First released was DisplayPort, so that is what many USB C alternate video mode devices use. Later came the USB C alternate mode HDMI video, which is NOT compatible with our Pinebook Pros.

As I said, it's complicated.

Just to be sure, sorry : the DisplayPort or HDMI modes have nothing to do with the physical socket ? Because mine is a HDMI and I dont change nothing to the physical connexion from one kernel to the other one. What sounds good is «As long as your hardware has worked once with your Pinebook Pro, then it's the right type», and I hope I will find out what to do to make it works with updated kernels…

[Arwen]

@alexandre Correct, the physical socket used on the external device, (dock or simple USB-C to video adapter), has little relation to what the Pinebook Pro exports electrically via the USB-C socket.

[alexandre]

Hi again ! Investigating the differences between the modules these two kernels load, i only find this : analogix_dp. The modinfo is pretty intersting :
description: Analogix DP Core Driver

and this page more : https://cateee.net/lkddb/web-lkddb/ROCKC...IX_DP.html

Could it be THE guy ?

[alexandre]

I read in the january blog post that «USB-C alt DP mode has now been merged in Manjaro’s default OS image for the Pinebook Pro». Is it a specific patch only for their distro or is it available in mainline linux so that it could save me ?

[alexandre]

For the experts that might read this. Here are my latest tries :

As i read the solution might have been found, i decided to try again a recent kernel (nadia's one not to mention her, and thanks again by the way). It still breaks the compatibility between pbp and my usb-c-hdmi-display. Then i though it might be because i use an old uboot version, so i upgraded it. But it still does not work. When i downgrade back to this good old kernel it works again (but with this new uboot, now i cant have just the external monitor without the laptop display !!! if i play a little bit too much with the XFCE applet for managing two displays, it even freezes the pbp with a quite scary red-green blinking led !)

If this can help…

alex