This is a weird issue, which I noticed when working on this pl=
ymouth fix:
https://gitlab.freedesktop.org/plymouth/plymouth/merge_requests/59
On boot to ensure a smooth handover of the framebuffer from plymouth to gdm=
the
following happens:
1) plymouth starts, does an addfb, becomes master, set the fb as the fb the
crtc should scanout
2) gdm starts tells plymouth to "deactivate", plymouth drops mast=
er (but does
not exit)
3) gdm becomes master, installs its own fb to scanout, the fb being scanned=
out
is now owned by gdm
4) gdm tells plymouth it may quit now
5) plymouth exits, without calling rmfb or closing the /dev/dri/card0 fd,
relying on the kernel to cleanup
6) all is well
The bug fix from the above merge requests make plymouth actually cleanup be=
hind
itself, this is necessary to avoid issues with hotunplug (see the plymouth =
MR
for details). My first attempt at this simply made plymouth always do the
cleanup, both on hotunplug and exit as that was the most straight forward to
do.
This changes the sequence to:
1-4) Idem as above
5) Plymouth internally calls src/plugins/renderers/drm/plugin.c:
ply_renderer_buffer_free() this does:
drmModeRmFB(...);
munmap (buffer->map_address, buffer->map_size);
destroy_dumb_buffer_request.handle =3D buffer->handle;
drmIoctl (fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroy_dumb_buffer_req=
uest);
Followed by calling close() on the fd.
6) Plymouth exits
7) 5 and/or 6 cause the gdm framebuffer being all messed up, it looks like a
wrong pitch or tiling setting
Note that when 5 is executed plymouth no longer is master and the fb being
removed is no longer being scanned out, so this really should not be able to
influence the current kms state, yet it does.
This is 100% reproducable for me with Fedora 30 + master plymouth + 5.3.0-r=
c7
on a R7 250E (SAPPHIRE Ultimate Radeon R7 250) using the amdgpu driver. I k=
now
that the default is to use the radeon driver with the R7 250E, but I was us=
ing
the amdgpu driver deliberately to reproduce:
https://b=
ugzilla.redhat.com/show_bug.cgi?id=3D1490490
For now I've modified the plymouth fix to only call ply_renderer_buffer_fre=
e()
+ close() on hot-unplug and to still leave cleanup to the kernel on exit, b=
ut
it would be nice to get to the bottom of this.