[PATCH] radeon: acquire BIOS via firmware subsystem if everything else failed

[Wilfried Klaebe]

tldr: works now, without patch, without GRUB, with efi-stub

Am Tue, Nov 25, 2014 at 05:25:50PM +0000 schrieb Matthew Garrett:
> On Tue, Nov 25, 2014 at 12:14:21PM -0500, Alex Deucher wrote:
> > The vbios image is available via ACPI prior to the OS taking over.
> > IIRC, Matthew Garret fixed up the bootloader to fetch the vbios image
> > prior to loading Linux so that it could be accessed after the OS
> > loaded.
> 
> EFI rather than ACPI, but yeah. In theory this should work fine if 
> you're using the EFI entry point. I don't know whether the patches for 
> linuxefi were ever accepted by grub upstream - if not, pushing those 
> would make more sense.

I could not find any patches for GRUB in this context. I did find big
numbers of web pages detailing how one would need to disable KMS to
use the radeon, or how to patch the radeon driver to load a vbios dump
from a file, or plain telling radeon didn't work. At least one for
about every Linux distribution I have heard of, and then some.

I could not find a way to use the EFI entry point from GRUB either.
Using the "linux" command was what never worked for me. I tried
"linuxefi", which complained about an invalid signature.

I then had a look at rEFInd again, upgraded it to the current version,
and then booted from rEFInd the same Linux 3.18-rc6 image (without the
patch) that did not work with GRUB earlier, and everything works ok.

Going to remove GRUB now :)

Sorry for any inconvenience...

Best regards,
Wilfried

---

Some details for others who might find this useful:

Hardware: MacBookPro8,2
Boot "chain": EFI -> rEFInd 0.8.3 ("gnuefi" variant) -> Linux 3.18-rc6
Kernel Commandline: "ro root=/dev/vg0/root video=radeondrmfb:1680x1050-32 at 60 radeon.dpm=1 video=inteldrmfb:1680x1050-32 at 60 i915.lvds_use_ssc=0 i915.lvds_downclock=1"