18734958e9
Modify the intel_idle driver to get the C-states information from ACPI _CST if the processor model is not recognized by it. The processor is still required to support MWAIT and the information from ACPI _CST will only be used if all of the C-states listed by _CST are of the ACPI_CSTATE_FFH type (which means that they are expected to be entered via MWAIT). Moreover, the driver assumes that the _CST information is the same for all CPUs in the system, so it is sufficient to evaluate _CST for one of them and extract the common list of C-states from there. Also _CST is evaluated once at the system initialization time and the driver does not respond to _CST change notifications (that can be changed in the future). The main functional difference between intel_idle with this change and the ACPI processor driver is that the former sets the target residency to be equal to the exit latency (provided by _CST) for C1-type C-states and to 3 times the exit latency value for the other C-state types, whereas the latter obtains the target residency by multiplying the exit latency by the same number (2 by default) for all C-state types. Therefore it is expected that in general using the former instead of the latter on the same system will lead to improved energy-efficiency. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
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| .. | ||
| intel_idle.c | ||
| Kconfig | ||
| Makefile | ||