*ERROR* failed to set phy pclock

Technical Support
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1

Hi team,

A customer is having issues with their 4K display unable to show any image with our Multimedia Image (5.7.2 and 6.1.0) at any resolution for our Apalis iMX8:

Apalis iMX8 V1.1E
Ixora V1.2A

We tried forcing the resolution both for 2K (Full HD) and 4K but no change. It seems to be an issue with the display but other Arm64 boards (RaspPi 3B+, RADXA ROCK3 ModelA) have no problem in showing image in the display.

We are getting different versions of this error:

[    7.172545] [drm] Initialized imx-drm 1.0.0 20120507 for display-subsystem on minor 1
[    7.314860] [drm] Mode: 1920x1080p148500
[    7.339849] [drm] Pixel clock: 148500 KHz, character clock: 185625, bpc is 10-bit.
[    7.339859] [drm] Pixel clk (148500 KHz) not supported, color depth (10-bit)
[    7.339890] [drm:cdns_hdmi_phy_set_imx8qm [cdns_mhdp_imx]] *ERROR* failed to set phy pclock
[    7.491729] imx-drm display-subsystem: fb0: imx-drmdrmfb frame buffer device

fbset shows the correct resolution.

We have made proper changes to Uboot and weston.ini to force a couple of resolutions but again, no image. Interestingly, also Toradex Easy Installer doesn’t show any image.

The display in question is a UP-M156T4K. I didn’t find anything special about this display.

Any idea? Thanks,
Alvaro.

2

Hello @alvaro.tx,

does the same setup work with another HDMI screen?
so it is only with this particular screen.

Best Regards,
Matthias Gohlke

3

Hi @matthias.tx , yes, other screens seem to be working fine.

Ideally, we want to avoid the cheap answer of “Please use another screen” especially if other Arm64 boards are working fine with it… Ideally we should fully understand the problem and solve it.

Kind regards,
Alvaro.

4

Hi @matthias.tx , the customer doesn’t have a lot of time to finish HW debug so any idea?

I’m checking here and there and it seems that the EDID data is not correctly read by the module OR that the data is correct but this is not supported by the drivers. If it is because of the display itself or because of the SOM/CB, that I don’t know.

5

we have to try this with the software team.
we had problems like this before.
Once is was just that the detect was not working with some cables.
I will check with Henrique later

6

Hi team,

We have new updates.

The customer managed to use 4K@29Hz by forcing it through Uboot like suggested here. However, we get the following error:

Apalis iMX8 # setenv tdxargs video=HDMI-A-1:3840x2160@29
...
TorizonCore 5.7.2-devel-20230218+build.723 apalis-imx8-07279051 ttyLP1

apalis-imx8-07279051 login: [   21.631161] [drm:cdns_hdmi_get_edid_block] *ERROR* get block[0] edid failed: -22
[   21.638618] [drm:cdns_hdmi_connector_get_modes] *ERROR* Invalid edid

apalis-imx8-07279051 login: [   43.385934] [drm:cdns_hdmi_get_edid_block] *ERROR* get block[0] edid failed: -22
[   43.393389] [drm:cdns_hdmi_connector_get_modes] *ERROR* Invalid edid

Also, we don’t want to force the resolution but make EDID work.

Interestingly, we also have some discoveries on the HW side (all using EDID):

Ixora + Multimedia Image
=> HDMI 4k display does not display anything including 4K30fps.
=> Another display with HDMI 1920x1080 will display

Ixora + TorizonCore (I just burned TorizonCore 5.7.0+build.17 (dunfell) from EasyInstaller. I want the display, so With Evaluation Container version specification)
=> HDMI 4k display does not display 4K30fps, but displays at 1024x768 (60Hz).
(There are times when it is not displayed and there is a sense of instability)

Custom board (based in Apalis EVB) + MultimediaImage
=> HDMI 4k display does not display anything including 4K30fps.
=> Another display with HDMI 1920x1080 will display

Custom board + TorizonCore (just burned TorizonCore 5.7.0+build.17 (dunfell) from EasyInstaller.)
=> HDMI 4k display does not display 4K30fps, but displays at 1024x768 (60Hz).

Custom board + TorizonCore with our app (+ our device tree overlay, our app not started)
=> HDMI 4k display does not display anything including 4K30fps.
=> Display HDMI 1920x1080 display (Portainer login screen)
=> Display 1920x1080 with DVI input (using HDMI->DVI conversion connector)

It seems that it does not depend on the customer custom board, but also Ixora is affected as well. Ideally maybe we should want we to display HDMI 4k30fps display with Ixora for this display (Which we confirmed it works at 4K@30 connecting it to a computer).

8

Hi @alvaro.tx !

I understood differently: from the thread you are referring to, the customer was able to use 4k@30 without forcing anything.

I remember using Apalis iMX8QM + Ixora on a 4k@30 without a problem. But I remember that the HDMI cable is the “weak link”. I could only make the 4k monitor work by using the cable that came with it. Any other random HDMI cable didn’t work.

I do not have an HDMI monitor with me this week, therefore I can’t exactly confirm right now.

Best regards,

9

Hi @henrique.tx , just FYI I have a 4k @ 30Hz screen and works fine for me. Seems to be the combination with this display.

No, the customer did not manage to get the 4k@30. Let me know where you get this since I might have expressed myself wrongly.

Thanks,
Alvaro.

10

Hi everyone, it seems the issue is that the Pixel Clock is not supported directly by the SW:
https://git.toradex.com/cgit/linux-toradex.git/tree/drivers/gpu/drm/imx/mhdp/cdns-mhdp-hdmi-phy.c?h=toradex_5.4-2.3.x-imx#n53

One could try to add their own monitor parameters here and see if it works.