Hello,
I have CCS 5.3 installed on Ubuntu 10.04, later I upgraded it to CCS 5.4. Then I installed BIOS-MCSDK 2.1.2.6. Due to a known issue http://e2e.ti.com/support/development_tools/code_composer_studio/f/81/p/268472/939376.aspx, the MCSDK package can't be added into RTSC depository.
So, I removed MCSDK 2.1.2.6, removed CCS 5.4, installed CCS 5.3, then installed MCSDK 2.1.2.6, unfortunately MCSDK can't be detected and added by CCS 5.3. Attached two screenshoots.
Regards, Eric