Re: ATI Radeon Mobility 3470 fails with Kernel 5.0

[Alex Deucher <alexdeucher@gmail.com>]

On Thu, Mar 24, 2022 at 2:07 AM Paul Menzel <pmenzel@molgen.mpg.de> wrote:
>
> Dear Craig,
>
>
> Am 24.03.22 um 02:09 schrieb Craig M:
> > I should add some further information:
> >
> > I have tried using Manjaro KDE, Kubuntu 20 and Kubuntu 18.03 live
> > disks and all exhibit this 'tearing' issue.
> >
> > The problem begins rather early on in the boot sequence while the TUI
> > is logging the startup information and continues to be a problem as
> > the screen becomes graphic.
> >
> > I feel that I should be able to rectify this with a setting change.
> >
> > Again, Thanks for any help.
> > Craig.
>
> In the future, it’d be great if instead of top-posting you used
> interleaved style.
>
> > On 3/24/22, Craig M <cmroanirgo@gmail.com> wrote:
> >> Hi,
> >>
> >> I'm trying to track down a problem with an ancient graphics device ATI
> >> Radeon Mobility 3470.
> >>
> >> Ubuntu/Kubuntu 18 is shipped kernel 4.18 and the radeon drivers work well.
> >> With 18.02 and later it ships with kernel 5.0 and the radeon drivers don't.
> >>
> >> What I'm seeing is hard to describe. It looks a lot like the scan
> >> lines are interleaved and there's a lot of noise. It's not the typical
> >> screen tearing, nor is it just snow (black and white noise). I can
> >> *just* make out what it being displayed onscreen, but hurts the eyes a
> >> lot to try and do so!
> >>
> >> If I hold the kernel back at 4.18 things are just fine.
> >>
> >> Some detailed info (from a working 4.18 kernel). Note that the
> >> returned information from a 5.x kernel isn't all that much different:
> >>
> >> $ lshw -c video
> >> *-display
> >>        description: VGA compatible controller
> >>        product: RV620/M82 [Mobility Radeon HD 3450/3470]
> >>        vendor: Advanced Micro Devices, Inc. [AMD/ATI]
> >>        physical id: 0
> >>        bus info: pci@0000:01:00.0
> >>        version: 00
> >>        width: 32 bits
> >>        clock: 33MHz
> >>        capabilities: pm pciexpress msi vga_controller bus_master
> >> cap_list rom       configuration: driver=radeon latency=0
> >> resources: irq:26 memory:c0000000-c7ffffff ioport:9000(size=256)
> >> memory:c8020000-c802ffff memory:c0000-dffff
> >>
> >>
> >> $ modinfo radeon
> >>
> >> filename:
> >> /lib/modules/4.18.0-17-generic/kernel/drivers/gpu/drm/radeon/radeon.ko
> >> license:        GPL and additional rights description:    ATI Radeon
> >> author:         Gareth Hughes, Keith Whitwell, others.
> >>
> >> ...
> >> name:           radeon
> >> vermagic:       4.18.0-17-generic SMP mod_unload
> >> signat:         PKCS#7
> >> signer:
> >> sig_key:
> >> sig_hashalgo:   md4
> >> ....
>
> Looking at the output of `dmesg` might also help.
>
> >> I'm just trying to track down the driver changes between 4.18 and 5.0
> >> to see what I can do to change settings. Any help  would be greatly
> >> appreciated. I've had a quick look through
> >> https://gitlab.freedesktop.org/xorg/driver/xf86-video-ati but I don't
> >> know where to start (as there's no correlation between releases and
> >> kernels, from what I can see).
>
> As switching the Linux kernel version works, you need to look at the
> driver in the Linux kernel. As you can easily reproduce your problem,
> and you are most likely alone with this old hardware, bisecting will
> probably the way to go. First you can try the packages from Ubuntu’s
> Kernel PPA [1]. Figuring out, in what version the regression occurs, you
> then build the Linux kernel yourself, for example with `make
> bindeb-pkg`, and try to find out the exact commit. There should be some
> guides on the WWW explaining all this in detail.

Yeah, as Paul said, bisecting is probably your best bet.  The radeon
driver has largely been in maintenance-only mode for the last few
years so it hasn't really seen any changes other than misc bug fixes
or cross component API changes.

Alex

>
>
> Kind regards and good luck,
>
> Paul
>
>
> PS: It would also be nice to know, if the problem is still present in
> Linux 5.17.
>
>
> [1]: https://kernel.ubuntu.com/~kernel-ppa/mainline/