I am new to the linux world and especially the hardware stuff. I know there are probably answers on this forum somewhere but it's hard to find. Basically I have centos 7 I think it says it's 3.10.0-1127.el.x86_64, not even sure if that's the version of kernel or what.
In a nutshell I have an onboard amd gpu.
I ran this :grep -E 'VGA|Display' and it says:
01:05.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] RS880 [Radeon HD 4250].

I installed drivers from amd site but nothing is working like it should. when i try to change the display setting it says its an "unknown monitor".

running this returns:
xrandr | grep -w connected
xrandr: Failed to get size of gamma for output default
default connected primary 1024x768+0+0 0mm x 0mm

So I don't know what to do to fix this stuff. The amd driver installed but evidently it's not loading? I've tried a ton of stuff from all the web sites I can find. Nothing works. I'm new to linux and don't quite understand what drivers to use or if I need to install any other than default one included with centos. Please help me I'm really lost on this one.
Roger

What made you believe you need a video driver from AMD instead of what is supplied by CentOS? Exactly how did you attempt to "change the display setting"? What model display have you connected? What cable type is used to connect to the display? That HD 4250 should work just fine with the CentOS-provided Radeon X driver. Nothing at all should be needed on your part for the Radeon DDX to do its job.

Please upload /var/log/Xorg.0.log to http://pastebin.com/ and provide the link to it here if you can't get X working properly after removing whatever AMD driver software you installed.

The reason this all started was I was getting message at boot about "no iommu?" not sure now what is said. Then after boot into graphic mode I wanted to add a resolution to the VGA monitor. I always used xrandr for that, but the monitor never listed anything but "Default Monitor". When I ran
xrandr | grep -w connected
that returned
xrandr: Failed to get size of gamma for output default
AGP: Your BIOS doesn't leave an aperture memory hole
[ 0.000000] AGP: Please enable the IOMMU option in the BIOS setup
Of course I'm not using AGP but the embedded controller.

I don't have any place in bios that I found to change that. My MB is old and no bios updates are available. The goal is to be able to set display to "1440x900" which I could do before I had to reinstall Centos 7 -1908. (same version I had). I'm not sure how to remove all the "junk" I have installed to try to fix this? I tried to attached a file for pastebin, Not sure it worked. This is the address: https://pastebin.com/raw/yJrzPgq1
Thanks,
Roger

These are the relevant errors reported in your log:The result of all these errors is X is using the VESA driver, which is a limited competence fallback unable in most cases to support any widescreen modes. Such errors commonly result from installation of a proprietary driver, or a kernel configuration that disables kernel modesetting (KMS), possibly due to blacklisting in /etc/modprobe.d/, or use of a kernel that does not support KMS. The Radeon DDX and the Modesetting DDX that should support the HD 4250 are thus blocked from use.

Another possibility is that firmware required for ATI GPUs has not been installed.

Attempting to install a proprietary driver could have created one or more *.conf files in /etc/X11/. If such files exist you could try renaming or otherwise removing them as the root user, or using root authority (su or sudo). Common names include xorg.conf, 50-device.conf, 50-monitor.conf and 50-screen.conf. Most users of ATI GPUs need none of such files for X setup automagic to work satisfactorily, but proprietary driver installers typically create one or more.

I'm not a CentOS user, so cannot make any specific suggestions how to tell which of these may apply in your installation. It may be best to proceed by asking the mods to move this thread to the CentOS subforum in the Linux-Distributions subforum, or start a new thread there pointing to this one, and using a subject line asking how to troubleshoot missing /dev/fb0 and missing /dev/dri/card0.

It's good to know at least the root of the problem. I'll do some research for that and if I need additional help I'll go back to the forum section for that.
I have a question about X11 I'm not sure what it does and if I need it? It seems like I installed it sometime during my trials and tribulations of trying to get resolution problem fixed. I think it kind of screwed some things up.

Thanks for your help
Roger

Good news! I found the radeon driver was blacklisted in /etc/modprobe.d/. Commented the line out and now have proper monitor listed and looks like I will be able to set my resolution with xrandr. How do i give you credit for help and close issue?

Thanks,
Roger

Great you found the simple solution!
Credit by clicking "Yes" in any useful/helpful post. Close should be in Thread Tools select list.

1 members found this post helpful.

I'm not sure I can revert back to this post, but after a automatic (I think) update the Amd driver is not loading again.
It looks like it is using vesa driver, but not sure.
The errors are a little different than before.
Where can i get help for this similar issue?

Thanks,
Roger

Pastebin /var/log/Xorg.0.log again so we can take a look.

Log file on paste bin:


https://pastebin.com/mwke5dRH

Thanks, Roger

That log shows /dev/dri/card0 and /dev/fb0 are missing (as in previous log), again preventing competent DDXes (radeon or modesetting) from being utilized, and thus the fallback to the crude VESA driver. I see no indication in the log why either is missing. Did the blacklisting get restored?

I had commented the blacklist file text out with # signs. It was still there with same lines commented out. I just deleted the text from file and saved it.
I'll reboot and check it now.

Still no good. same problem

This seems to be more a driver/software issue than a hardware issue. Maybe posting in CentOS, Software or Desktop forums would generate interest in this from a CentOS user. I only ever used CentOS as a brief test many years ago. A lot of X improvements have been made since CentOS's 3.10 kernel was current (June 2013).

Additional information might help find a cause:
1-dmesg
2-journalctl
e.g.or simply perusing the two for anomalies.

output from the suggested cmd:

]# dmesg | grep -i failed
[ 0.170105] acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM
[ 1.161770] i8042: Failed to disable AUX port, but continuing anyway... Is this a SiS?
[ 2.284548] r600_cp: Failed to load firmware "radeon/RS780_pfp.bin"
[ 2.284596] [drm:r600_init [radeon]] *ERROR* Failed to load firmware!
[ 2.291846] radeon: probe of 0000:01:05.0 failed with error -2
[ 14.254635] spl: module verification failed: signature and/or required key missing - tainting kernel

this line has me wondering "radeon/RS780_pfp.bin" From what I have found before the driver should be RS880. Not sure if this matters?

if there might be a better place on this forum to look i can move it there.