Kernel modesetting hangs my boot, but the ATI driver requires it

I have a late 2011 MacBook Pro. It has an integrated Intel video card and a discrete ATI video card. Ideally, I'd like my Xorg to use the ATI card with the free driver (no Catalyst). Here's the problem: kernel modesetting hangs my boot (verified by adding nomodeset to kernel parameters), and I can't figure out why. However, the ATI driver _requires_ KMS, as does the Intel driver. What are my options for getting graphics with the desired setup as described above? I'm on kernel 3.13.8, Arch GNU/Linux. I've also tried it with kernel 3.10.35, AKA the LTS kernel. No luck. As suggested in comments, I've tried to ping the affected machine after it locks up. I can't tell for sure, but it appears that it's completely frozen, not just the display. I've also tried booting into Mac OS X and using gfxCardStatus to force using the Intel card. This did nothing. In order to try to get more information, I've booted the MacBook with the following kernel parameters appended to my normal kernel line (the regular kernel, not the LTS kernel, and with quiet removed), and with gfxCardStatus set to on-the-fly switching (this seemed to revert automatically on a reboot of OS X): rootwait ignore_loglevel debug debug_locks_verbose=1 sched_debug initcall_debug mminit_loglevel=4 udev.log_priority=8 loglevel=8 earlyprintk=vga,keep log_buf_len=10M print_fatal_signals=1 apm.debug=Y i8042.debug=Y drm.debug=1 scsi_logging_level=1 usbserial.debug=Y option.debug=Y pl2303.debug=Y firewire_ohci.debug=1 hid.debug=1 pci_hotplug.debug=Y pci_hotplug.debug_acpi=Y shpchp.shpchp_debug=Y apic=debug show_lapic=all hpet=verbose lmb=debug pause_on_oops=5 panic=10 sysrq_always_enabled When I try to start GDM using either the ATI or Intel drivers, booted without KMS, Xorg fails with a message about not finding a suitable driver (expected, since the Intel/AMD drivers need KMS). I've also tried using the xf86-video-vesa package, but that fails with a message about having a suitable driver but not having a suitable configuration - something about the BIOS not being right. I've tried using PRIME , but since I can't get Xorg to come up even without acceleration or anything fancy, xrandr doesn't work and I can't even get past the first step. I've thought about using vgaswitcheroo or something related, but I don't think that will do anything due to the fact that the underlying issue is, I believe, the fact that KMS is hanging. The final thing I've tried is using the proprietary Catalyst driver, due to the fact that it has it's own KMS implementation, but I couldn't get it to install due to an Xorg server version mismatch. And honestly, I have less than zero desire to use a proprietary driver if I can help it, so I didn't try very hard. I've sent the Linux Kernel Mailing List an email about this, and hopefully someone will get back to me. Is it possible that I've run into a kernel bug or an Xorg bug worth reporting? I've Googled, but nothing helpful's come up.