X session fails with ATI Radeon HD 4670 - KMS /radeon driver

NeddySeagoon · Posted: Mon Jul 20, 2020 9:57 pm Post subject:

Pums,

There are lots of ways of keeping the build box and clients in sync and sharing and installing the binaries once you have them.
You can share the repo(s) and binaries over NFS.
Set up some form of server.
Sync using rsync ... which is what portage uses to update the local copy of the repo.

As you say, its all in the guide that you linked.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Pums · n00b Joined: 03 Jun 2020 Posts: 52

EDIT: Actually, it's easy to summarize it all, no real need to read more: radeon's module is the culprit. If I blacklist it at boot (modprobe.blacklist=radeon), I can have a console, log in, run commands... But X doesn't work. With radeon, black screen, no visible console, no visible prompt, I can startx but can't see anything and twm is "defunct". Shouldn't I try to build it (EDIT: ie. radeon) in along with the firmwares?

The following is useless umho...
-----
I did several trials (I did not use nomodeset boot kernel parameter) . I think 2) is the really interesting one, so maybe read it first:

1) A minimalistic kernel (-v3), based on one that I have working fine on the powerful computer, I've only tried to make changes for it to handle the mac's hardware config (specially radeon graphic driver and network devices).

On boot, screen is completely black (no "loading iniramfs", no prompt, nothing; with previous kernels, screen used to turn black after displaying openrc's "Checking local filesystems"). Like with previous kernels, though I can't see anything at all on the screen, I can log in on a tty and startx. sshd works and I could check that X seemed to start, with a defunct twm process, as it happened already.

* zcat /proc/config.gz
* dmesg (the first line shows "(root@sed2)", sed2 is the powerful computer that made the kernels; Mac's hostname is "mac". I did not change conf.d/hostname nor /etc/host in the chroot tree, it still has the default "localhost". I don't know whether it can be a problem and I'd rather change that.)
* lspci -nnk
* lsmod
* Xorg.0.org

2) I used a genkernel's default config kernel (-v5), but I forgot to copy the corresponding modules in /lib/modules. For the first time ever, I could boot Linux without nomodeset parameter and display was right, regular console prompt, I could log in, run commands. But, logically, no network, plenty of errors and startx fails immediately.

* zcat /proc/config.gz (but modules were not used !)
* dmesg
* lsmod
* lspci -nnk
* Xorg.0.org

3) If I use the same kernel and add the forgotten modules for this kernel in /lib/modules, it seems like it used to be with older kernels: screen turns black after displaying some openrc messages, no prompt, nothing. startx results just like with the minimalistic kernel: twm defunct, screen empty since boot time.

Config is the same as -v5, but modules were usable.

*dmesg
*lsmod
*lspci -nnk
*Xorg.0.log

I've used this xorg.conf:

Pums · n00b Joined: 03 Jun 2020 Posts: 52

I've made a new kernel (v6) with minimalistic configuration, with built-in radeon driver and firmware:

theotherjoe · Guru Joined: 22 Nov 2003 Posts: 393

Pums,

from dmesg in 2) one can see that there is no display problem as long as the system
only plays with the efifb VGA console.

Now, I have been through the dmesg ouput in your last post and from what I see there
is no indication of problems with the radeondrmfb.

I have a hunch but since I dont have much experience with apple hardware I might
be on a wrong track.
My suspicion is that there is nothing wrong with the radeon driver. The backlight driver
simply turns off the backlight, hence you cant see anything on the screen once
radeon driver has taken over.
I wonder what would happen if you would compile the apple backlight driver into the kernel
(just like the radeon driver) instead of having it as a module?

Pums · n00b Joined: 03 Jun 2020 Posts: 52

theotherjoe,

Although I don't understand much (see personal note below), I've made a new kernel (-v7) retrieving the previous config (-v6) only with the change you've suggested (CONFIG_BACKLIGHT_APPLE=y).

I could not see any difference with -v6 kernel : some messages displayed very quickly, and screen turns black even before openrc shows anything, no visible prompt, no visible console; from that moment screen remains empty, if I startx "blindly" from a tty, "ps -A" shows a "defunct" twm process.

Child_of_Sun_24 · Guru Joined: 28 Jul 2004 Posts: 578

Do you have CONFIG_DRM_FBDEV_EMULATION enabled in your kernel config ?

It's under Device Drivers -> Graphics support -> Direct Rendering Manager (XFree86 4.1.0 and higher DRI support) -> Enable legacy fbdev support for your modesetting driver

Maybe it helps.

Pums · n00b Joined: 03 Jun 2020 Posts: 52

theotherjoe · Guru Joined: 22 Nov 2003 Posts: 393

well, Pums,
as I said, I might be wrong there

Mrs Google also didnt come up with a solution but it seems to be
a known problem. Found a thread from ubuntuforums about iMac with radeon.
describing the same problem with the console and without any solution.
Best bet would probably be to disable framebuffer console altogether and
go with plain VGA console:
Graphics support --> Console display driver support -->
Framebuffer Console support
That leaves the problem around Xorg. You probably will have to play
with the two options for the radeon driver, compiled into kernel or as module

edit: tried without framebuffer console on my system. but that clashes with
kernel mode setting

that reduces your options even furher.

edit2: found this article about Macs EFI and Linux, maybe
you can get some clues from it
http://refit.sourceforge.net/myths/

Pums · n00b Joined: 03 Jun 2020 Posts: 52

Thank you very much,

I need to understand better how Linux handles graphic hardware . I have tracks to explore and I will run tests in the next few days. I'll tell you more if needed.

Eventually, we may find or not a solution, but anyway I'll have learnt a lot thanks to the help I've received!

NeddySeagoon · Posted: Fri Jul 24, 2020 6:29 pm Post subject:

Pums,

When you prevent the radeon kernel module loading, you get a console with some other console driver.

The xorg radeon driver depends on the kernel radeon modesetting driver.
You can have Xorg but only with the vesa or fb xorg drivers.

Radeon and the modesetting driver both depend on kernel modesetting, which as you rightly conclude, is the source of your problem.

Pums · n00b Joined: 03 Jun 2020 Posts: 52

Well, I had missed that... And it seems the key problem.

I've been looking around about it. I think I have to make a hybrid MBR/GPT partition table on my hard drive. By default it's pure UEFI, I don't think I can boot in legacy mode on this computer, there's no system setup menu like with traditional UEFI or old BIOS style. Actually, it seems the way Apple handles UEFI is strange. According to what I could see, macOS doesn't really use the EFI partition, it boots "directly". For example, even I lose access to macOS on boot after installing grub/grub2 (it doesn't recognize macOS), I can still boot on it by typing "alt" on boot (and then I can choose between launching macOS, macOS recovery mode, or booting on an external media in case there is a bootable one). The EFI partition is here but seems inactive until you install an external bootmanager on it.

See : https://support.apple.com/en-qa/HT201255

I need to back up my datas and then try to do that.

Thanks again!

NeddySeagoon · Posted: Sat Jul 25, 2020 9:49 am Post subject:

Pums,

Without some BIOS code the graphics card will not initialise.

When the BIOS (not EFI) starts, at the end of its startup, before it loads the MBR, it calls the initialisation routines on all the peripherals that it detected.
The peripherals can assume the presence of BIOS and call subroutines provided by the BIOS ROM.
It gets worse ... I think that the BIOS is 16 bit real mode code, so you need the CPU in real mode.

The EFI Firmware is 32 bit protected mode and that won't run 16 bit real mode.

The kernel can execute 16 bit real mode code. That's required for some emulators, but it has no supporting BIOS code.

You need some actual BIOS code and a way to run it, like BIOS booting.
It has to run before the kernel sets up its DRM so that the hardware is in the state the kernel expects.

Changing the partition table on it own won't help.

What's required is reverse engineering the graphics card setup routines and working out what they do, then writing new code to achieve the same thing that runs as a part of the kernel before DRM is started. That's hard. Its been done once but not maintained.
MacOS must do it ... but its not open source.

-- Edit --
Very long hacky work around ... maybe.
Do a very minimal install on the Mac hardware to set it up as a Virtual Machine host. That's all it will do.
No Xorg, No user apps ...
Pass the video card through to the the guest. This means that the bare metal host will have no video at all. It will be serial console if there is a serial port, or ssh or even VNC.
The video pass though can be a boot time option. You would need two kernels.

Set up a guest that does BIOS booting. As it uses BIOS, it will correctly initalise the Graphics card.
This is your user install.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Pums · n00b Joined: 03 Jun 2020 Posts: 52

NeddySeagoon,

About the first part of your last post, reverse engineering... writing new code... All that is light years away from my current capacities. I'm just a very very basic Gnu/Linux end-user that has been trying out Gentoo for over three months. I love it, I've learnt a lot (I didn't even know what a chroot is... and actually I believe it's still not clear for me how it really works...), I like keeping on learning, I'm not afraid of spending time on that but there are many things I can't realisticly do. My code skills do not go much beyond "hello world".

About the second part, well, it's a bit the same... My experience in virtualization has been limited to toying around with Vmware or Virtualbox (nothing to do...), and installing once a host-0 Xen kernel on Debian (I guess it's rather the kind of thing you're talking about ?), and boot on it just to see, though I actually never used it.

In brief, to do that I would need to be almost guided step by step, and I can't guarantee I won't do things wrong. If you're ready to try it, well I could never thank you enaugh for that, but of course, feel free to do it or not. If I can use ssh I think it's ok not to have video at all (no serial port on the mac), that's more or less what I've been doing lately...

So, tell me if I'm wrong, the first step with what you suggest would be reinstalling gentoo from scratch using a single stable profile? And... set it as a Virtual Machine host, across Xen eg?

Anon-E-moose · Posted: Sat Jul 25, 2020 8:23 pm Post subject:

I haven't followed every post, but does the mac have a display port connection and have you tried it to see if it shows a difference?
_________________
PRIME x570-pro, 3700x, 6.1 zen kernel
gcc 13, profile 17.0 (custom bare multilib), openrc, wayland

Pums · n00b Joined: 03 Jun 2020 Posts: 52

Pums · n00b Joined: 03 Jun 2020 Posts: 52

NeddySeagoon,

I've been looking around about virtualization, reading and rereading your last post and I think I figure out the solution you consider.

As you suggest, I'm going to make a new basic install for a Xen domain-0 following Gentoo's Xen wiki's page, to begin. I'll tell more if needed.

NeddySeagoon · Posted: Sun Jul 26, 2020 8:52 pm Post subject:

Pums,

I would use a KVM because that's what I'm used to for bare metal installs on systems that will only host Virtual Machines.
I use Virtual Box too, for quick setups, where I only need the guest for a short time.

I have never used Xen. Well, once, a long time ago, I rented a Xen virtual machine but that was it.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Pums · n00b Joined: 03 Jun 2020 Posts: 52

Ok, so it'll be the first time I use qemu.

I made a new minimalistic install from scratch, tried to follow only the handbook and the kernel instructions for qemu, though I have doubts since it seems several config options of the wiki's qemu installation page do not match with the current stable kernel version.

I included in the new kernel the hardware modules matching with the mac, radeon driver included (I had doubt about the "pass the video card through to the the guest" point). Logically screen turns black at boot time... ssh is ok. No video (as you said) meant no radeon driver I guess (now). Should I make a new kernel without radeon driver? It's easy to do it with the fast computer.

I included KVM for Intel processors support as a module:

NeddySeagoon · Posted: Mon Jul 27, 2020 3:03 pm Post subject:

Pums,

You need the PCI_STUB option in the host kernel

Pums · n00b Joined: 03 Jun 2020 Posts: 52

I've tried to search and read many things, it's quite hard and many stuff seems outdated.

I think my host kernel is ok. I've followed this GEntoo's wiki page about Qemu.

Edit: About libvirt to control a VM remotely (though I'm not sure it's so important now), did you think of virt-manager for example ? (it's the only available on Gentoo I could find)

I also tried to follow this page about GPU passthrough with libvirt qemu kvm on Gentoo's wiki and this similar page (this last one is the only I could find that gave explicitly an option to boot on old BIOS mode):

NeddySeagoon · Posted: Sat Aug 01, 2020 8:13 pm Post subject:

Pums,

From

Pums · n00b Joined: 03 Jun 2020 Posts: 52

I don' know how to make KVM work.

It seems there's a problem with libvirtd:

DaggyStyle · Watchman Joined: 22 Mar 2006 Posts: 5909

Pums · n00b Joined: 03 Jun 2020 Posts: 52

It is, since I'm actually just trying to have X session / KMS working with the mentionned GPU, and it seems the only solution would be to make a GPU passthrough to a virtual machine.

DaggyStyle · Watchman Joined: 22 Mar 2006 Posts: 5909