ATI Radeon Mobility 3470 fails with Kernel 5

[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.

On 3/24/22, Craig M <cmroanirgo at 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 at 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
> ....
>
>
>
> 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).
>
> Regards,
> Craig.
>