garbled screen with RPI4 on 5.10-rc2

[Stefan Schake]

On Tue, Nov 3, 2020 at 1:12 PM Lucas Nussbaum <lucas at debian.org> wrote:
>
> Salut Maxime,
>
> On 03/11/20 at 12:32 +0100, Maxime Ripard wrote:
> > On Mon, Nov 02, 2020 at 11:19:57PM +0100, Lucas Nussbaum wrote:
> > > Hi,
> > >
> > > I'm getting a half-garbled screen with an RPI4 on linux 5.10-rc2 (which
> > > includes Maxime Ripard's changes to the VC4 DRM driver).
> > >
> > > Photo: https://blop.info/pub/rpi4-vc4.jpg
> > >
> > > dmesg output: https://blop.info/pub/dmesg.txt
> > >
> > > Including:
> > > [    0.000000] Kernel command line: video=HDMI-A-1:1920x1080M at 60,margin_left=48,margin_right=48,margin_top=48,margin_bottom=48 dma.dmachans=0x71f5 bcm2709.boardrev=0xd03114 bcm2709.serial=0x99e79233 bcm2709.uart_clock=48000000 bcm2709.disk_led_gpio=42 bcm2709.disk_led_active_low=0 smsc95xx.macaddr=DC:A6:32:BE:A2:01 vc_mem.mem_base=0x3ec00000 vc_mem.mem_size=0x40000000  console=tty0 console=ttyS1,115200 root=/dev/mmcblk1p2 rw elevator=deadline fsck.repair=yes net.ifnames=0  rootwai
> > >
> > > This is with a Debian image from https://raspi.debian.net/, where I just
> > > upgraded the kernel. I also tried updating *.{dat,elf,bin} from
> > > https://github.com/raspberrypi/firmware/tree/master/boot, but it did not
> > > help.
> > >
> > > Any ideas?
> >
> > It's weird. It's on a 1080p display, right? Anything special about it?
>
> No, the display's normal resolution is 2560x1440.
>
> xrandr (on my laptop, connected to that screen) says:
> HDMI-1 connected primary 2560x1440+1920+0 (normal left inverted right x axis y axis) 597mm x 336mm
>    2560x1440     59.95*+
>
> > Can you share your config.txt too?
>
> $ cat /boot/firmware/config.txt
> arm_64bit=1
> enable_uart=1
> upstream_kernel=1
> kernel=vmlinuz-5.10.0-rc2
> initramfs initrd.img-5.10.0-rc2
>
> Should I try to force the video= parameter according to
> https://www.raspberrypi.org/documentation/configuration/config-txt/video.md ?
>

Your kernel command line from the initial post seems to already have a

video=HDMI-A-1:1920x1080M at 60

setting, and this will override any HDMI detection.