I want to add another data point for a card not yet mentioned in this bug.  I
have had this issue for quite some time, awaiting a fix.  I run a fully-updated
Debian testing, and my card is described below.

XFX R9 270X
Vendor ID: 1002
Device ID: 6810
Subsystem Vendor ID: 1682
Subsystem Device ID: 9275

I don't believe this matches the existing quirk, and I haven't created a custom
kernel to add one.  Running with radeon.drm=0 allows it to boot and basically
function, but with very poor 3D performance.

I'd be more than happy to provide any additional diagnostic information within
my abilities to collect, and test any potential fixes.