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BayTrail SoC - PUnit writes


Bay Trail -I SoC which has 30679 D0 Stepping Processor 

Microcode Versions tried 





MSR 79 – writes microcode to SoC (Passed) 

MSR 8b – Reads microcode revision (Passed)


Hang at below code


; For A-step, bits 0 and 1 need to be set after patch load and before MRC (first possible reset)

;Without setting BIOS_RESET_DONE on A0, Bios will stuck at vlvdxe after GT PowerManagement

 ; Could be done later in flow for B-step, but no need to move and have it in 2 places.


;Program BIOS_RESET_DONE (bit0) and BIOS_ALL_DONE (bit1) in PUNIT.BIOS_RESET_CPL, Port 0x4, Offset 0x5

;BIOS_ALL_DONE is newly added bit for B0.



mov   edx, 0CF8h    ;config MCD 

mov   eax, 800000d4h 

out   dx, eax 

mov   edx, 0CFCh    ;set Bit0 and Bit1 

mov   eax, 3 

out   dx, eax 


mov   edx, 0CF8h    ;config MCR 

mov   eax, 800000d0h 

out   dx, eax 


mov   edx, 0CFCh    ;write_opcode+portID+offset 

mov   eax, 007040510h 

out   dx, eax  


why there is a Hang at this register write? when i remove this code , boot goes ahead and hangs at GT Power Management.when i disable both, Graphics does not come up

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Hi rrao1,


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