ACPI: Add function to write _PPC using NVS
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>
diff --git a/src/arch/x86/boot/acpigen.c b/src/arch/x86/boot/acpigen.c
index 71aa10c..47845a0 100644
--- a/src/arch/x86/boot/acpigen.c
+++ b/src/arch/x86/boot/acpigen.c
@@ -396,6 +396,32 @@
return len;
}
+/* generates a func with max supported P states */
+int acpigen_write_PPC_NVS(void)
+{
+/*
+ Method (_PPC, 0, NotSerialized)
+ {
+ Return (PPCM)
+ }
+*/
+ int len;
+ /* method op */
+ acpigen_emit_byte(0x14);
+ len = acpigen_write_len_f();
+ len += acpigen_emit_namestring("_PPC");
+ /* no fnarg */
+ acpigen_emit_byte(0x00);
+ /* return */
+ acpigen_emit_byte(0xa4);
+ /* arg */
+ len += acpigen_emit_namestring("PPCM");
+ /* add all single bytes */
+ len += 3;
+ acpigen_patch_len(len - 1);
+ return len;
+}
+
int acpigen_write_TPC(const char *gnvs_tpc_limit)
{
/*