Re: kern/49964: DRM/KMS panic on Radeon hardware

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

The following reply was made to PR kern/49964; it has been noted by GNATS.

From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
To: gnats-bugs%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost, gnats-admin%NetBSD.org@localhost
Cc: 
Subject: Re: kern/49964: DRM/KMS panic on Radeon hardware
Date: Thu, 22 Oct 2015 23:08:30 +0000

 A few iterations of debugging prints later, it looks like
 
 (a) the machine has a good-looking vbios at [0xc0000, 0xdffff], shown
 by `dd if=/dev/mem of=/tmp/vbios bs=1 iseek=786432 count=131072', but
 
 (b) for some reason, pci_find_rom reads 0x00 0x00 from 0xc0000 0xc0001
 instead of the expected magic numbers 0x55 0xaa, when called via
 pci_map_rom/pci_map_rom_md in sys/external/bsd/drm2/include/linux/pci.h.
 
 I'm at a loss about why this might be.
 
 I don't think it should be necessary to enable the ROM address decoder
 in the PCI BAR in order to read from 0xc0000 -- that should work even
 with pre-PCI code, I think.