intelthermal: Add Intel Processor Thermal driver

[guest-seuros]

Summary

Add driver for Intel Processor Thermal Device (B0D4) found on Skylake and later processors.
This device exposes RAPL power limits (PL1/PL2) and TDP information via sysctl.

The driver reads MSR_RAPL_POWER_UNIT to determine the correct power unit scaling factoor, with fallback to 1/8 W if MSR read fails.

Sysctls provided:

dev.intelthermal.0.pl1              - Long-term power limit (mW)
dev.intelthermal.0.pl2              - Short-term power limit (mW)
dev.intelthermal.0.tdp              - Thermal Design Power (mW)
dev.intelthermal.0.pl1_enabled      - PL1 enabled flag
dev.intelthermal.0.pl2_enabled      - PL2 enabled flag
dev.intelthermal.0.locked           - Firmware lock status
dev.intelthermal.0.access_denied    - MMIO access status
dev.intelthermal.0.power_unit_div   - Power unit divisor
dev.intelthermal.0.power_unit_shift - Power unit shift

Note: Later generations may have different MMIO layouts and would need per-generation validation. I used the gen 10th documentation (that match the hardware i used)

[guest-seuros]

Wire into build; add PL2 enabled/lock bit; align sysctl names

[guest-seuros]

Rename to intelthermal for consistency; add man page

[guest-seuros]

@ziaee , shall we name this driver intelthermal or intel_thermal to mirror acpi_thermal < already in tree ?

PS: this diff need rebasing/fix once D54881 land.

[olce]

In D54882#1291723, @guest-seuros wrote:

@ziaee , shall we name this driver intelthermal or intel_thermal to mirror acpi_thermal < already in tree ?

PS: this diff need rebasing/fix once D54881 land.

Yes, I'm all in favor of it, and I checked with srcmgr@ that having underscores is OK.

[olce]

In D54882#1291731, @olce wrote:

Yes, I'm all in favor of it, and I checked with srcmgr@ that having underscores is OK.

Meaning intel_thermal(4), if that wasn't clear.

[imp]

There's no issues with _ in driver names unless it gets too carried away: _i_n_t_e_l___t_h_e_r_m_a_l_ would be right out.

Though we generally try to have the driver module match the driver name, and here they don't match. So I'd suggest renaming the module to intel_thermal as well.

[ziaee]

! In D54882#1291723, @guest-seuros wrote:
@ziaee , shall we name this driver intelthermal or intel_thermal to mirror acpi_thermal < already in tree ?

intel_thermal is much better for consistency with acpi_thermal. I was not intending to say that underscores are prohibited in the other review, I was intending to say that naming the driver exactly what a different named in linux is confusing, especially because the "_core" appendix is not mentioned in my glance through the datasheets or any other doc and also seems like a lot of underscores. Sorry for the confusion.

[ziaee]

share/man/man4/intelthermal.4

1–5 ↗

(On Diff #175349)

please consider using the preferred license template for all of these. in the last one, you changed just the one in the manual and the driver was committed with the other files still showing this style.

[guest-seuros]

.

[guest-seuros]

remove stale _intel_pmc_core from modules Makefile