Private bug reported:
With "Above 4G MMIO" enabled in BIOS, EFI FB driver cannot get 64-bit FB
address on Raven1 platform.
Then fail to initialize EFI FB driver.
That results in black-screen for console mode or installing Ubuntu
system.
e.g. if the FB address is 0x7fc80000000, EFI FB could only get the low 32-bit
FB address.
[ 0.992990] efifb: probing for efifb
[ 0.992995] efifb: cannot reserve video memory at 0x80000000
[ 0.992999] ioremap on RAM at 0x0000000080000000 - 0x00000000808cffff
As my investigation, it looks Ubuntu efi boot stub cannot get 64-bit address by
GOP.
1) create a EFI shell app to get the fb address, it’s 64-bit
2) Build bzImage.efi to load 4.13 custom kernel, efifb driver also could get
64-bit address.
** Affects: amd
Importance: High
Status: New
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https://bugs.launchpad.net/bugs/1736862
Title:
[Raven1] EFI FB driver cannot get 64-bit FB address with "Above 4G
MMIO" enabled in Ubuntu16.04.3
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