Dear Maintainer,

I recently performed a successful text install of Debian Buster using
a snapshot from
<https://cdimage.debian.org/cdimage/weekly-builds/amd64/iso-cd/debian-testing-amd64-netinst.iso>.
That install was minimal, i.e., there were no extra packages installed
beyond those absolutely required by the text installer.  I then
followed up by using that minimal Debian system to install
xserver-xorg-video-amdgpu (generally recommended for new chipsets like
the Polaris 12) and other X-related packages.  But I specifically
excluded firmware-amd-graphics because that was only a suggestion
(i.e., not a dependency of xserver-xorg-video-amdgpu), and I try to
avoid using firmware blobs as far as possible for all the obvious
practical as well as free software reasons.  However, all subsequent
attempts to configure X for my AMD RX 550 (Polaris 12) card, failed at
or near the detection stage with messages similar to the following:

[180858.109] (II) AMDGPU: Driver for AMD Radeon:
        All GPUs supported by the amdgpu kernel driver
[180858.109] (II) [KMS] drm report modesetting isn't supported.
[180858.109] (EE) Screen 0 deleted because of no matching config section.
[180858.109] (II) UnloadModule: "amdgpu"
[180858.109] (EE) Device(s) detected, but none match those in the config file.

That is a ambiguous error message because no details are given here or
elsewhere in the error log.  Also, no issues were reported by
/var/log/messages and /var/log/syslog.  However, dmesg did have an
drm-related error message concerning firmware (sorry, lost the
details) which eventually lead me to reluctantly install what turns
out to be the absolutely essential (at least for the RX 550)
firmware-amd-graphics package.  At first that installation made no
difference until I realized you also had to reboot for the firmware
to take effect.  After that (text) reboot, I issued the

startx

command, X recognized this graphics card, and X came up without an
issue.  I suspect to reproduce the bad behaviour above with this model
of graphics cards (and likely other modern AMD GPU's as well) all you
will have to do is to purge the firmware-amd-graphics package, perform
a text reboot, and then issue "startx".

In sum, the issues are

1. Ambiguous error messages (at least within this log file) for the
situation when firmware-amd-graphics is not installed for at least this RX 550
Polaris 12 chipset.

2. You cannot even get started with X configuration with this hardware
unless the firmware-amd-graphics is installed.  This is, of course,
consistent with the statement "Some [AMD] GPUs may require firmware to
operate the X Window System" at
<https://wiki.debian.org/AtiHowTo#Firmware>, but at least a table of
which AMD chipsets (such as my Polaris 12) where this is an issue
would be extremely useful at that website since it would reduce a lot
of hair-pulling by Debian users like me who try to avoid firmware whenever
that is possible.

Thanks for your packaging efforts that have made it possible for me
to use this card (albeit with firmware) and best wishes,

Alan

Alan and bug 899086,

Please try testing if this situation is improved or fixed in debian
testing (to soon become bullseye) images, similarly to as you did
before.

In fact the cdimage address you linked seems to be still exactly correct!.

I'd like to see bug-report either closed or updated for bullseye.
Given all the changes/massive improvements in amdgpu modesetting
I expect the situation to be considerably improved, at least!.