tree fb7eb741d1eb6324e944a537e82487a58ed8b5d7
parent e930360bbe2239723ea9f7c493860053a069e71f
author Felix Held <felix-coreboot@felixheld.de> 1678141900 +0100
committer Felix Held <felix-coreboot@felixheld.de> 1678276811 +0000

soc/amd/common/block/acpi/cpu_power_state: add get_cstate_info helper

Introduce the get_cstate_info helper function that populates the caller-
provided cstate_values array with the data returned by the SoC-specific
get_cstate_config_data function. From the array get_cstate_config_data
returns, only the ctype, latency and power fields are used, so the rest
can be left uninitialized. Those 3 fields are compile-time constants.
For each entry, write_cstate_entry will generate the corresponding
resource information from the given data. In the C1 case where ctype is
1, the state is entered via a MWAIT instruction, while the higher C
states are entered by doing an IO read from a specific IO address. This
IO address is x - 1 bytes into the IO region starting at
MSR_CSTATE_ADDRESS for the Cx state. So for example C2 is entered by
reading from the C state IO base address + 1. This resource information
is generated during runtime, since the contents of MSR_CSTATE_ADDRESS
aren't necessarily known at compile-time.

MAX_CSTATE_COUNT is introduced so that the caller can allocate and pass
a buffer with space for the maximum number of C state entries. This
maximum number corresponds to the number of IO addresses the CPU traps
beginning from MSR_CSTATE_ADDRESS. In practice, it's unlikely that more
than 3 or maybe 4 C states will be available though.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I2c36c1d604ced349c609882b9d9fe84d5f726a8d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73428
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>