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
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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"