hdmi_mode discrepancies?

[Altivo]

I am using a VGA monitor and an active HD to VGA converter box.

Debian and Raspbian perform well with hdmi_group=2 and hdmi_mode=16 in config.txt. This sets 1024x768 resolution at 60Hz, if I'm understanding the documentation correctly.

The same settings with Arch produce no video output at all. I'd have thought this portion of the setup was largely concerned with firmware rather than the OS about to be loaded. However, Arch produces a video display with hdmi_mode=17 (1024x768 @70Hz) and works with the 800x600 modes at both frequencies. I haven't tested, but I suspect that hdmi_mode=16 in Arch is forcing the output to the composite video jack rather than HDMI.

I can, of course, just use the mode 17 setting, but the display on my monitor is a bit jittery at 70Hz where it is rock steady at 60Hz. Raspbian shows similar behavior, except that the 60Hz choice does function there. In Arch it produces nothing, and the three monitors I've tried report "no signal."

Why would the same mode setting produce such different results between the two Linux distros?

[I note that the config.txt docs say "do not use" for hdmi_mode=15. Could it possibly be that Arch is blocking hdmi_mode=16 rather than 15?]

[JeremyF]

Do they have the same firmware version?

Code: Select all

/opt/vc/bin/vcgencmd version

[Altivo]

Interesting. Using this command (logged in as root) as you suggest

/opt/vc/bin/vcgencmd version

On Raspbian gets the following result

Jul 14 2012 13:14:40
Copyright (c) 2012 Broadcom
version 325444 (release)

But on Arch gets this error

/opt/vc/bin/vcgencmd: error while loading shared libraries: libvcos.so: cannot open shared object file: no such file or directory

libvcos.so is in fact present in the /opt/vc/lib directory on both installations

[pepedog]

cp -a /opt/vc/lib/* /usr/lib/

One of our devs has tweaked firmware package, whatever start.elf file you choose for ram configuration, it gets carried on to new firmware.
pacman -Syu to update

[Altivo]

OK, I ran 'pacman -Syu' and it did update the firmware along with a couple of other smaller things.

I copied the /opt/vc/lib files to /lib/usr and now the vcgencmd runs.

Firmware version on Arch is 328039, dated July 28 2012 now.
Firmware version on Raspbian is 325444, dated July 14 2012.

Arch still puts out no HDMI signal with hdmi_mode=16, while Raspbian does work correctly with the same setting of 16. Both Arch and Raspbian work with hdmi_mode=17.

[pepedog]

Only one person can answer this, Dom (popcornmix)
Its likely to be firmware and not kernel, you can report here with as much info as possible
https://github.com/raspberrypi/firmware ... state=open
Thanks
Dave

[Altivo]

Ugh. I'm reluctant to start filing reports on actual developer forums. While I'm very familiar with Linux as a user and network administrator, I'm definitely not at the developers' level of technical skill and awareness. In the past when I've tried putting an oar into those waters I've been quickly rebuffed and dismissed.

I'll leave it that there's something not quite right between the two distributions and somewhere along the line it's going to have to be examined by a person who understands exactly what's going on. Can't be my hardware, because that works fine with Raspbian and did before that with Debian "squeeze." Can't be my config.txt because I've actually recopied the working one from Raspbian to Arch, and it still fails in Arch.

[sdjf]

If pepedog is saying to report the problem, he knows what he is talking about and you should not get rebuked or rebuffed. You seem to have done an excellent job of defining the problem, others who have the same problem may not understand things well enough to go into the details you have already mapped out. Please do reconsider and post the link to your report here if you go ahead.