dductil Not Working With DVI-D Cable?

claudici · 2021-01-06 17:31:39

I have a 1080p 144hz ASUS VG248QE monitor for my desktop (and also laptop). I had a DisplayPort cable connecting it to my PC's graphics card (AMD RX 580) but I switched it out for a DVI-D cable (basically the same; supports 144hz) because I wanted to use the DP for my laptop's docking station as DVI-D doesn't support 144 hz with my docking station for whatever reason. But that's not my issue.

The issue I am having is that I want to set my monitor's backlight using ddcutil but it isn't working with the DVI-D cable.

I know for a fact that my monitor supports DDC because I was able to set the brightness using ddcutil when the DP cable was connected. I didn't touch anything else, just swapped the cables.

Things I've tested for:

i2c_dev is loaded:

$ lsmod | grep i2c
i2c_dev                24576  0
i2c_algo_bit           16384  1 amdgpu
i2c_i801               36864  0
i2c_smbus              20480  1 i2c_i801

I am running the dductil command as root so permissions shouldn't be an issue:

 $ sudo ddcutil detect --verbose
Output level:               Verbose
Reporting DDC data errors:  false
Trace groups active:        none
Traced functions:           none
Traced files:               none
Force I2C slave address:    false
User defined features:      disabled

Performance and Retry Options:
   Deferred sleep enabled:                      false
   Sleep suppression (reduced sleeps) enabled:  false
   Dynamic sleep adjustment enabled:            false

Invalid display
   I2C bus:             /dev/i2c-5
      I2C address 0x50 (EDID) responsive: true
      Is eDP device:                      false
      I2C address 0x37 (DDC) responsive:  true
      /sys/bus/i2c/devices/i2c-5/name:   AMDGPU DM i2c hw bus 4
   EDID synopsis:
      Mfg id:           ACI
      Model:            VG248
      Serial number:    E3LMQS076290
      Manufacture year: 2014
      EDID version:     1.3
      Product code:     9441
      Binary sn:        16843009 (0x01010101)
      Extra descriptor:
      Video input definition: 0x80 - Digital Input
      Supported features:
         DPMS standby
         DPMS suspend
         DPMS active-off
         Digital display type: RGB 4:4:4
         Standard sRGB color space: False
      White x,y:        0.313, 0.329
      Red   x,y:        0.650, 0.329
      Green x,y:        0.331, 0.622
      Blue  x,y:        0.151, 0.053
      Extension blocks: 1
   EDID source:
   EDID hex dump:
              +0          +4          +8          +c            0   4   8   c
      +0000   00 ff ff ff ff ff ff 00 04 69 e1 24 01 01 01 01   .........i.$....
      +0010   0d 18 01 03 80 35 1e 78 ea 9d e5 a6 54 54 9f 26   .....5.x....TT.&
      +0020   0d 50 54 b7 ef 00 71 4f 81 80 81 40 81 c0 81 00   .PT...qO...@....
      +0030   95 00 b3 00 01 01 02 3a 80 18 71 38 2d 40 58 2c   .......:..q8-@X,
      +0040   45 00 13 2b 21 00 00 1e 00 00 00 fd 00 32 96 1e   E..+!........2..
      +0050   a0 21 00 0a 20 20 20 20 20 20 00 00 00 fc 00 56   .!..      .....V
      +0060   47 32 34 38 0a 20 20 20 20 20 20 20 00 00 00 ff   G248.       ....
      +0070   00 45 33 4c 4d 51 53 30 37 36 32 39 30 0a 01 02   .E3LMQS076290...
   DDC communication failed
   Is DDC/CI enabled in the monitor's on-screen display?

$ env | grep DISPLAY
DISPLAY=:0

And just to be safe I double-checked that DDC/CI was enabled in the monitor's settings.

DDC should work with DVI-D, right??? I have no idea what the problem is.

Last edited by claudici (2021-01-06 17:59:46)

Ropid · 2021-01-07 05:43:50

This person here has a very similar problem:

https://github.com/rockowitz/ddcutil/issues/152

You should try that "--sleep-multiplier=4" argument that the person mentioned, maybe it'll work for you.

That bug report there is also using amdgpu driver (you can find an "amdgpu" text somewhere in the paste-bin text). I'm then guessing this could be an issue with the amdgpu driver because the person tried the monitor on a different computer and DDC worked over VGA.

The bug tracker for the amdgpu kernel module is here if you want to report it:

https://gitlab.freedesktop.org/drm/amd/ … =%E2%9C%93

I can't find good search results there looking for "ddc dvi".

About how to solve the problem right now, the only idea I have is buying another DP cable.

Last edited by Ropid (2021-01-07 05:44:02)

claudici · 2021-01-07 06:02:33

Ropid wrote:

This person here has a very similar problem:
https://github.com/rockowitz/ddcutil/issues/152
You should try that "--sleep-multiplier=4" argument that the person mentioned, maybe it'll work for you.
That bug report there is also using amdgpu driver (you can find an "amdgpu" text somewhere in the paste-bin text). I'm then guessing this could be an issue with the amdgpu driver because the person tried the monitor on a different computer and DDC worked over VGA.
The bug tracker for the amdgpu kernel module is here if you want to report it:
https://gitlab.freedesktop.org/drm/amd/ … =%E2%9C%93
I can't find good search results there looking for "ddc dvi".
About how to solve the problem right now, the only idea I have is buying another DP cable.

I tried that argument but sadly it did not work.

I will look into making a bug report later.

And unfortunately my monitor only has one DisplayPort connector so I can't use two DP without using another monitor. So I think tomorrow I will swap the cables again and just use the DVI-D for the laptop. Not a big deal really.

Last edited by claudici (2021-01-07 06:04:37)

Arch Linux

#1 2021-01-06 17:31:39

dductil Not Working With DVI-D Cable?

#2 2021-01-07 05:43:50

Re: dductil Not Working With DVI-D Cable?

#3 2021-01-07 06:02:33

Re: dductil Not Working With DVI-D Cable?

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