[XS] Change in coreboot[main]: mb/google/{rex,ovis}: epp set to 45% for mtl performance expectation

[Sukumar Ghorai (Code Review)]

Attention is currently required from: Dinesh Gehlot, Eran Mitrani, Kapil Porwal, Paul Menzel, Subrata Banik, Tarun.

Sukumar Ghorai has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/79386?usp=email )

Change subject: mb/google/{rex,ovis}: epp set to 45% for mtl performance expectation
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Patch Set 3:

(5 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/79386/comment/08baf12b_d772c50c :
PS3, Line 7: epp set to 45% for mtl performance expectation
> Maybe: […]

Acknowledged

https://review.coreboot.org/c/coreboot/+/79386/comment/fddaad2c_504b0f3e :
PS3, Line 9: which is deemed insufficiently
           : aggressive for meeting the MTL performance expectations in
           : balance_performance mode.
> According to whom? Also, what does that mean exactly? It’s drawing too much power?

EPP=45% is giving the required performance with very minimum power impact. This is revirewd internally.

https://review.coreboot.org/c/coreboot/+/79386/comment/3815807a_5033ee73 :
PS3, Line 12: #cat
> Please add a space after #.

Acknowledged

https://review.coreboot.org/c/coreboot/+/79386/comment/308705b4_9600c9ef :
PS3, Line 11: balance_performance mode.
            :   #cat /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference
            :   balance_performance
            :   # iotools rdmsr 0 0x774
            :   0x0000000080003f06
            : EPP=45% is giving the required performance in MTL.
> I’d follow Markdown and intend code blocks with four spaces. […]

Acknowledged

https://review.coreboot.org/c/coreboot/+/79386/comment/4f2258ce_9360fa47 :
PS3, Line 20: # iotools rdmsr 0 0x774
            :      0x0000000073003d06
> How can the value be interpreted?

Details as in Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 4: Model-Specific Registers.
Also mentioned in patch - here is snapshot:
   set EPP to 45%: 45 * 256/100 = 115 = 0x73 
  MSR 0x774 IA32_HWP_REQUEST [31:24] Energy/Performance Preference (R/W)