nouveau unhappy with EFI

[Patrick Welche <prlw1%cam.ac.uk@localhost>]

With biosboot set on the root partition of a GPT disk, I can now biosboot
or EFI boot the same computer.

Thanks to mlelstv@'s hint, I can get a serial console on the EFI side with
consdev com,0x3f8,115200
as well as the biosbooting side.

In both cases, booting with the serial console, X works on this nouveau
GeForce GTX 680.

However, if I boot without the serial console. I see nothing on screen in
the EFI case, but all is OK in the biosboot case. (Unsure: typing blindly
I did not get X to start in the EFI case, but fat fingering possible.)

Apart from hard disk probe ordering differences, this is all I see
when comparing the dmesgs:

$ diff -u bios_with_nv_com.dmesg efi_with_nv_com.dmesg 
--- bios_with_nv_com.dmesg      2019-07-29 09:58:10.390398272 +0100
+++ efi_with_nv_com.dmesg       2019-07-29 08:59:02.186251104 +0100
@@ -13,29 +13,31 @@
 Kernelized RAIDframe activated
 running cgd selftest aes-xts-256 aes-xts-512 done
 timecounter: Timecounter "i8254" frequency 1193182 Hz quality 100
+efi: systbl at pa db67f018
 System manufacturer System Product Name (System Version)
 mainbus0 (root)
-ACPI: RSDP 0x00000000000F05B0 000024 (v02 ALASKA)
-ACPI: XSDT 0x00000000D143E098 0000AC (v01 ALASKA A M I    01072009 AMI  00010013)
-ACPI: FACP 0x00000000D144A788 000114 (v06 ALASKA A M I    01072009 AMI  00010013)
-ACPI: DSDT 0x00000000D143E1E0 00C5A3 (v02 ALASKA A M I    01072009 INTL 20120913)
+ACPI: RSDP 0x00000000CA802000 000024 (v02 ALASKA)
+ACPI: XSDT 0x00000000CA8020A0 0000B4 (v01 ALASKA A M I    01072009 AMI  00010013)
+ACPI: FACP 0x00000000CA80E790 000114 (v06 ALASKA A M I    01072009 AMI  00010013)
+ACPI: DSDT 0x00000000CA8021E8 00C5A3 (v02 ALASKA A M I    01072009 INTL 20120913)
 ACPI: FACS 0x00000000DA931D80 000040
-ACPI: APIC 0x00000000D144A8A0 00015E (v03 ALASKA A M I    01072009 AMI  00010013)
-ACPI: FPDT 0x00000000D144AA00 000044 (v01 ALASKA A M I    01072009 AMI  00010013)
-ACPI: FIDT 0x00000000D144AA48 00009C (v01 ALASKA A M I    01072009 AMI  00010013)
-ACPI: SSDT 0x00000000D144AAE8 0000FC (v02 ALASKA CPUSSDT  01072009 AMI  01072009)
-ACPI: SSDT 0x00000000D145BCA8 0000BF (v01 AMD    AMD PT   00001000 INTL 20120913)
-ACPI: SSDT 0x00000000D144AC40 008C98 (v02 AMD    AMD ALIB 00000002 MSFT 04000000)
-ACPI: SSDT 0x00000000D14538D8 00322C (v01 AMD    AMD AOD  00000001 INTL 20120913)
-ACPI: MCFG 0x00000000D1456B08 00003C (v01 ALASKA A M I    01072009 MSFT 00010013)
-ACPI: HPET 0x00000000D1456B48 000038 (v01 ALASKA A M I    01072009 AMI  00000005)
-ACPI: SSDT 0x00000000D1456B80 000024 (v01 AMDFCH FCHZP    00001000 INTL 20120913)
-ACPI: UEFI 0x00000000D1456BA8 000042 (v01                 00000000      00000000)
-ACPI: IVRS 0x00000000D1456BF0 0000D0 (v02 AMD    AMD IVRS 00000001 AMD  00000000)
-ACPI: SSDT 0x00000000D1456CC0 002314 (v01 AMD    AMD CPU  00000001 AMD  00000001)
-ACPI: CRAT 0x00000000D1458FD8 000F50 (v01 AMD    AMD CRAT 00000001 AMD  00000001)
-ACPI: CDIT 0x00000000D1459F28 000029 (v01 AMD    AMD CDIT 00000001 AMD  00000001)
-ACPI: SSDT 0x00000000D1459F58 001D4A (v01 AMD    AmdTable 00000001 INTL 20120913)
+ACPI: APIC 0x00000000CA80E8A8 00015E (v03 ALASKA A M I    01072009 AMI  00010013)
+ACPI: FPDT 0x00000000CA80EA08 000044 (v01 ALASKA A M I    01072009 AMI  00010013)
+ACPI: FIDT 0x00000000CA80EA50 00009C (v01 ALASKA A M I    01072009 AMI  00010013)
+ACPI: SSDT 0x00000000CA80EAF0 0000FC (v02 ALASKA CPUSSDT  01072009 AMI  01072009)
+ACPI: SSDT 0x00000000CA81FCE8 0000BF (v01 AMD    AMD PT   00001000 INTL 20120913)
+ACPI: SSDT 0x00000000CA80EC48 008C98 (v02 AMD    AMD ALIB 00000002 MSFT 04000000)
+ACPI: SSDT 0x00000000CA8178E0 00322C (v01 AMD    AMD AOD  00000001 INTL 20120913)
+ACPI: MCFG 0x00000000CA81AB10 00003C (v01 ALASKA A M I    01072009 MSFT 00010013)
+ACPI: HPET 0x00000000CA81AB50 000038 (v01 ALASKA A M I    01072009 AMI  00000005)
+ACPI: SSDT 0x00000000CA81AB88 000024 (v01 AMDFCH FCHZP    00001000 INTL 20120913)
+ACPI: UEFI 0x00000000CA81ABB0 000042 (v01                 00000000      00000000)
+ACPI: BGRT 0x00000000CA81ABF8 000038 (v01 ALASKA A M I    01072009 AMI  00010013)
+ACPI: IVRS 0x00000000CA81AC30 0000D0 (v02 AMD    AMD IVRS 00000001 AMD  00000000)
+ACPI: SSDT 0x00000000CA81AD00 002314 (v01 AMD    AMD CPU  00000001 AMD  00000001)
+ACPI: CRAT 0x00000000CA81D018 000F50 (v01 AMD    AMD CRAT 00000001 AMD  00000001)
+ACPI: CDIT 0x00000000CA81DF68 000029 (v01 AMD    AMD CDIT 00000001 AMD  00000001)
+ACPI: SSDT 0x00000000CA81DF98 001D4A (v01 AMD    AmdTable 00000001 INTL 20120913)
 ACPI: 8 ACPI AML tables successfully acquired and loaded
@@ -475,7 +477,7 @@
 nouveau0: info: NVIDIA GK104 (0e4000a2)
 nouveau0: info: bios: version 80.04.09.00.01
 nouveau0: info: fb: 2048 MiB GDDR5
-Zone  kernel: Available graphics memory: 11312638 kiB
+Zone  kernel: Available graphics memory: 11312672 kiB
 Zone   dma32: Available graphics memory: 2097152 kiB
 nouveau0: info: DRM: VRAM: 2048 MiB
 nouveau0: info: DRM: GART: 1048576 MiB
@@ -495,10 +497,65 @@
 kern info: [drm] Driver supports precise vblank timestamp query.
 nouveau0: info: DRM: MM: using COPY for buffer copies
 nouveaufb0 at nouveau0
-nouveaufb0: framebuffer at 0xffffac825badb000, size 3840x2160, depth 32, stride 15360
+nouveaufb0: framebuffer at 0xffff97825bacd000, size 3840x2160, depth 32, stride 15360
 wsdisplay0 at nouveaufb0 kbdmux 1
 wsmux1: connecting to wsdisplay0