Similar to SPR, the C1 and C1E states on ADL are mutually exclusive.
Only one of them can be enabled at a time.
But contrast to SPR, which usually has a strong latency requirement
as a Xeon processor, C1E is preferred on ADL for better energy
efficiency.
Add custom C-state tables for ADL with both C1 and C1E, and
1. Enable the "C1E promotion" bit in MSR_IA32_POWER_CTL and mark C1
with the CPUIDLE_FLAG_UNUSABLE flag, so C1 is not available by
default.
2. Add support for the "preferred_cstates" module parameter, so that
users can choose to use C1 instead of C1E by booting with
"intel_idle.preferred_cstates=2".
Separate custom C-state tables are introduced for the ADL mobile and
desktop processors, because of the exit latency differences between
these two variants, especially with respect to PC10.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
[ rjw: Changelog edits, code rearrangement ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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