Samsung C27F390: Invalid display and DDC communication failed

[PataviniMa]

I have a Samsung C27F390 connected (via HDMI) to my laptop running Ubuntu 22.04 Jammy. Latest version of ddcutil 2.1.4 installed via ppa. I can't seem to be able to run any core functionality: "detect" returns "Invalid display", and and even a simple "getvcp" call returns "DDC communication failed". One thing to note: I used to run Win10 on this machine with the same exact setup, and I was perfectly able to get/set VCP values with no issues, using tools like ControlMyMonitor. Here is the output of environment and interrogate commands.

Any help would be much appreciated.

[rockowitz]

Looking at the interrogate output, it looks like the monitor is returning bad data. Try executing command ddcutil detect --verbose --ddcdata --stats and submit the output. Also, does option --sleep-multiplier 2.0 improve things? It can sometimes, but not always, slow I2C communication down enough for DDC communication to work.

[PataviniMa]

Thanks for your answer. Here is the output of the detect command. Adding the option --sleep-multiplier 2.0 to the detect command doesn't seem to have any effect:

Invalid display
   I2C bus:  /dev/i2c-4
   DRM connector:           card1-HDMI-A-1
   EDID synopsis:
      Mfg id:               SAM - Samsung Electric Company
      Model:                C27F390
      Product code:         3378  (0x0d32)
      Serial number:        H4ZN804225
      Binary serial number: 1113212234 (0x425a454a)
      Manufacture year:     2020,  Week: 33
   DDC communication failed. (getvcp of feature x10 returned Error_Info[DDCRC_RETRIES in ddc_write_read_with_retry, causes: DDCRC_DDC_DATA(10)])

[rockowitz]

Confirmed bad data is coming from the monitor. Other than increasing sleep time and retrying requests, there's nothing more ddcutil can do.

Some users have had success using a modified i915 driver that lowers the I2C bus speed. See this i915 enhancement request for details on how this was done. Even if you are not comfortable building your own i915 driver, I suggest you add yourself as an interested party to the report.