So Ive apparently got bad rlc firmware from last Dec:

[jimc@groucho ~]$ sum radeon-fw/* /lib/firmware/radeon/CEDAR_* | sort
05888     3 /lib/firmware/radeon/CEDAR_rlc.bin
23436     3 radeon-fw/CEDAR_rlc.bin
35913    24 /lib/firmware/radeon/CEDAR_smc.bin
35913    24 radeon-fw/CEDAR_smc.bin
45275     6 /lib/firmware/radeon/CEDAR_me.bin
45275     6 radeon-fw/CEDAR_me.bin
55341     5 /lib/firmware/radeon/CEDAR_pfp.bin
55341     5 radeon-fw/CEDAR_pfp.bin
[jimc@groucho ~]$ ll /lib/firmware/radeon/CEDAR_*
-rw-r--r--. 1 root root  5504 Dec 23  2012 /lib/firmware/radeon/CEDAR_me.bin
-rw-r--r--. 1 root root  4480 Dec 23  2012 /lib/firmware/radeon/CEDAR_pfp.bin
-rw-r--r--. 1 root root  3072 Dec 23  2012 /lib/firmware/radeon/CEDAR_rlc.bin
-rw-rw-r--. 1 root root 23888 Aug  7 15:18 /lib/firmware/radeon/CEDAR_smc.bin

The odd errors I saw now have a "usual suspect",
I'll reboot with rc5 but still missing fw to see what bootlog looks like,
then update that fw, and reboot again.