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ACPI: Add function to write _PPC using NVS

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The existing NVS variable for PPCM will be used to
select a dynamic max P-state.

By itself this does not change existing behavior because
the NVS PPCM variable is initialized to zero.

PPCM can be tested by building and booting a modified BIOS
that sets gnvs->ppcm to a value greater than 1 and checking
from the OS that the P-state is limited to that value.

Change-Id: Ia7b3bbc6b84c1aa42349bb236abee5cc92486561
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/1341
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
This commit is contained in:
Duncan Laurie
2012-07-16 12:11:53 -07:00
committed by Ronald G. Minnich
parent 10d31aba76
commit 0eefa00503
3 changed files with 28 additions and 1 deletions
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2
src/cpu/intel/model_206ax/acpi.c
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@ -251,7 +251,7 @@ static int generate_P_state_entries(int core, int cores_per_package)
len = acpigen_write_empty_PCT();
/* Write _PPC with no limit on supported P-state */
len += acpigen_write_PPC(0);
len += acpigen_write_PPC_NVS();
/* Write PSD indicating configured coordination type */
len += acpigen_write_PSD_package(core, cores_per_package, coord_type);