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@60 radeon.dpm=1 video=inteldrmfb:1680x1050-32@60 i915.lvds_use_ssc=0 i915.lvds_downclock=1"
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