Dear Maintainer,
This is my AMD Radeon graphics card: https://www.visiontek.com/radeon-7750-2gb-gddr5-6m-6x-minidp.html
It has 6 (six!) mini-DisplayPorts to attach six displays.
By email, I confirmed with the vendor, VisionTek, that this graphics card supports:
6x display @ 4K (3840 x 2160) @ 60Hz refresh
They are 100% confident the Microsoft Windows driver supports this setup.
Originally, my monitor setup was: 4x @ 4K (3840 x 2160) @ 60Hz refresh
I tried to add monitor #5 (also 4K and supports 60Hz refresh), but I was required to reduce the refresh rate to 30Hz.
At 60Hz, KDE graphics would "go insane" where all monitors not display correctly.
Sorry, my description is poor, but it is hard to describe the video effect.
It is a bit like when the "tracking" was incorrect on a 1990s VCR, and your TV would look like rubbish!
To confirm: I have carefully tested a few things on my side:
I unplugged my monitor #4 and I can see monitor #5 runs fine at 4K (3840 x 2160) @ 60Hz refresh.
Thus, I can say with /some/ confidence it is not an issue with the monitor.
I also tried a few different DisplayPort cables -- no improvement.
More: This workstation is a brand new build (during the COVID-19 crisis), so I am sure my montherboard and CPU
has sufficient PCIe lanes to support the card:
Mobo: ASUS PRIME X570-PRO (https://www.asus.com/Motherboards-Components/Motherboards/All-series/PRIME-X570-PRO/)
CPU: AMD Ryzen 9 3900X 12-Core Processor
I do have this non-free package installed: firmware-amd-graphics
... and here: /var/log/syslog -- I can see:
///
Dec 4 10:07:06 cwb kernel: [ 1.452689] [drm] radeon kernel modesetting enabled.
Dec 4 10:07:06 cwb kernel: [ 1.452737] radeon 0000:08:00.0: vgaarb: deactivate vga console
Dec 4 10:07:06 cwb kernel: [ 1.453708] Console: switching to colour dummy device 80x25
Dec 4 10:07:06 cwb kernel: [ 1.453829] [drm] initializing kernel modesetting (VERDE 0x1002:0x683F 0x1545:0x7750 0x00).
Dec 4 10:07:06 cwb kernel: [ 1.453852] radeon 0000:08:00.0: No more image in the PCI ROM
Dec 4 10:07:06 cwb kernel: [ 1.453868] ATOM BIOS: VT
Dec 4 10:07:06 cwb kernel: [ 1.454025] radeon 0000:08:00.0: VRAM: 2048M 0x0000000000000000 - 0x000000007FFFFFFF (2048M used)
Dec 4 10:07:06 cwb kernel: [ 1.454026] radeon 0000:08:00.0: GTT: 2048M 0x0000000080000000 - 0x00000000FFFFFFFF
Dec 4 10:07:06 cwb kernel: [ 1.454028] [drm] Detected VRAM RAM=2048M, BAR=256M
Dec 4 10:07:06 cwb kernel: [ 1.454028] [drm] RAM width 128bits DDR
Dec 4 10:07:06 cwb kernel: [ 1.454061] [TTM] Zone kernel: Available graphics memory: 32920280 KiB
Dec 4 10:07:06 cwb kernel: [ 1.454062] [TTM] Zone dma32: Available graphics memory: 2097152 KiB
Dec 4 10:07:06 cwb kernel: [ 1.454063] [TTM] Initializing pool allocator
Dec 4 10:07:06 cwb kernel: [ 1.454065] [TTM] Initializing DMA pool allocator
Dec 4 10:07:06 cwb kernel: [ 1.454080] [drm] radeon: 2048M of VRAM memory ready
Dec 4 10:07:06 cwb kernel: [ 1.454080] [drm] radeon: 2048M of GTT memory ready.
Dec 4 10:07:06 cwb kernel: [ 1.454087] [drm] Loading verde Microcode
Dec 4 10:07:06 cwb kernel: [ 1.454109] radeon 0000:08:00.0: firmware: direct-loading firmware radeon/verde_pfp.bin
Dec 4 10:07:06 cwb kernel: [ 1.454119] radeon 0000:08:00.0: firmware: direct-loading firmware radeon/verde_me.bin
Dec 4 10:07:06 cwb kernel: [ 1.454127] radeon 0000:08:00.0: firmware: direct-loading firmware radeon/verde_ce.bin
Dec 4 10:07:06 cwb kernel: [ 1.454134] radeon 0000:08:00.0: firmware: direct-loading firmware radeon/verde_rlc.bin
Dec 4 10:07:06 cwb kernel: [ 1.454146] radeon 0000:08:00.0: firmware: direct-loading firmware radeon/verde_mc.bin
Dec 4 10:07:06 cwb kernel: [ 1.454161] radeon 0000:08:00.0: firmware: direct-loading firmware radeon/verde_smc.bin
Dec 4 10:07:06 cwb kernel: [ 1.454163] [drm] Internal thermal controller with fan control
Dec 4 10:07:06 cwb kernel: [ 1.460563] [drm] radeon: dpm initialized
Dec 4 10:07:06 cwb kernel: [ 1.460605] radeon 0000:08:00.0: firmware: direct-loading firmware radeon/TAHITI_uvd.bin
Dec 4 10:07:06 cwb kernel: [ 1.460627] radeon 0000:08:00.0: firmware: direct-loading firmware radeon/TAHITI_vce.bin
Dec 4 10:07:06 cwb kernel: [ 1.461296] [drm] Found VCE firmware/feedback version 50.0.1 / 17!
Dec 4 10:07:06 cwb kernel: [ 1.461302] [drm] GART: num cpu pages 524288, num gpu pages 524288
Dec 4 10:07:06 cwb kernel: [ 1.530380] [drm] PCIE GART of 2048M enabled (table at 0x00000000001D6000).
Dec 4 10:07:06 cwb kernel: [ 1.530473] radeon 0000:08:00.0: WB enabled
Dec 4 10:07:06 cwb kernel: [ 1.530474] radeon 0000:08:00.0: fence driver on ring 0 use gpu addr 0x0000000080000c00
Dec 4 10:07:06 cwb kernel: [ 1.530474] radeon 0000:08:00.0: fence driver on ring 1 use gpu addr 0x0000000080000c04
Dec 4 10:07:06 cwb kernel: [ 1.530474] radeon 0000:08:00.0: fence driver on ring 2 use gpu addr 0x0000000080000c08
Dec 4 10:07:06 cwb kernel: [ 1.530475] radeon 0000:08:00.0: fence driver on ring 3 use gpu addr 0x0000000080000c0c
Dec 4 10:07:06 cwb kernel: [ 1.530475] radeon 0000:08:00.0: fence driver on ring 4 use gpu addr 0x0000000080000c10
Dec 4 10:07:06 cwb kernel: [ 1.530633] radeon 0000:08:00.0: fence driver on ring 5 use gpu addr 0x0000000000075a18
Dec 4 10:07:06 cwb kernel: [ 1.550571] radeon 0000:08:00.0: fence driver on ring 6 use gpu addr 0x0000000080000c18
Dec 4 10:07:06 cwb kernel: [ 1.550572] radeon 0000:08:00.0: fence driver on ring 7 use gpu addr 0x0000000080000c1c
Dec 4 10:07:06 cwb kernel: [ 1.550685] radeon 0000:08:00.0: radeon: MSI limited to 32-bit
Dec 4 10:07:06 cwb kernel: [ 1.550725] radeon 0000:08:00.0: radeon: using MSI.
Dec 4 10:07:06 cwb kernel: [ 1.550749] [drm] radeon: irq initialized.
///
I am not a Linux wizard, but that looks pretty reasonable to my eyes -- I *think* the non-free firmware gets loaded.
Idea: I found an Linux AMD graphics driver mailing list here:
https://lists.freedesktop.org/mailman/listinfo/amd-gfx
Reading their mail archives, it looks very techincal (basically people discussing code patches from the graphics driver),
so I thought it was inappropriate to raise this issue on their mailing list.
However, would it be useful if I ask on that mailing list if this display setup is supported by the driver?
Display setup: 6x display @ 4K (3840 x 2160) @ 60Hz refresh
My point: I assume that list is run by experts on AMD hardware & drivers... and might quickly say: "Oh, we know about that.
No, that isn't supported on Linux and we don't plan to support it (or whatever)."
Finally: I am somewhat embarrassed to raise this bug ticket. Truly, it is a luxury to /attempt/ to connect five monitors
to a KDE/Debian/GNU/Linux workstation! However, since I do have the hardware available, it might be useful to provide
debug info and try a few things with Linux driver experts who support it.
Thank you in advance for your attention.
If I can provide any other useful debug info, or try different things, please let me know.
Regards,
Kevin Connor ARPE
Hongkong