[coreboot-gerrit] [S] Change in coreboot[main]: cpu/intel/model_206ax: Allow PL1/PL2 configuration

[Anastasios Koutian (Code Review)]

Attention is currently required from: Angel Pons, Patrick Rudolph, Paul Menzel.

Anastasios Koutian has posted comments on this change by Anastasios Koutian. ( https://review.coreboot.org/c/coreboot/+/83269?usp=email )

Change subject: cpu/intel/model_206ax: Allow PL1/PL2 configuration
......................................................................

Patch Set 2:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/83269/comment/afe7f342_ecb8985f?usp... :
PS2, Line 9: Tested on ThinkPad T420 with the i7-3940XM.
> Can you please elaborate, how you tested this?

Set pl1=35000000 and pl2=43750000 microwatts in t420/devicetree.cb

Built and flashed

Confirmed power limits are 35000000 and 43750000 in sysfs intel-rapl-msr interface:
`$ cat /sys/devices/virtual/powercap/intel-rapl/intel-rapl:0/constraint_0_power_limit_uw`
and
`$ cat /sys/devices/virtual/powercap/intel-rapl/intel-rapl:0/constraint_1_power_limit_uw`

Also confirmed the same limits are applied in MCHBAR:
`$ MSR_PKG_POWER_LIMIT=0x610`
`$ MCH_PKG_POWER_LIMIT_LO=0xfed159a0`
`$ MCH_PKG_POWER_LIMIT_HI=0xfed159a4`
`$ sudo iotools mmio_read32 "${MCH_PKG_POWER_LIMIT_LO}"` => 0x00dc8118
`$ sudo iotools mmio_read32 "${MCH_PKG_POWER_LIMIT_LO}"` => 0x0000815e
`$ sudo rdmsr -c "${MSR_PKG_POWER_LIMIT}"` => 0x815e00dc8118

Finally, run stress test:
`$ stress-ng -c 8 --cpu-method matrixprod`
while monitoring processor package power using Intel PCM (https://github.com/intel/pcm)