The recommendation from Intel is to report each core as a
separate logical domain in the _PSD table.
This goes against the recommendation in the ACPI specification
because all of these cores are on the same package and share a
VR so they will do voltage transitions together.
The reasoning is that with a larger number of logical processors
the P-state often ramps too quickly resulting in higher power
consumption. By exposing each core as a separate domain the OS
can manage them individually allowing the socket to select the
optimum frequency.
BUG=chrome-os-partner:16862
BRANCH=none
TEST=manual: boot on wtm2, read and verify the ACPI _PSD table in
the SSDT and ensure each core is in a separate domain.
$ cat /sys/firmware/acpi/tables/SSDT > /tmp/SSDT
$ iasl -d /tmp/SSDT
Processor (\_PR.CPU0, 0x00, 0x00000000, 0x00)
{
Name (_PSD, Package (0x01)
{
Package (0x05)
{
0x05,
0x00,
0x00000000,
0x000000FE,
0x00000001
}
})
}
Processor (\_PR.CPU1, 0x01, 0x00000000, 0x00)
{
Name (_PSD, Package (0x01)
{
Package (0x05)
{
0x05,
0x00,
0x00000001,
0x000000FE,
0x00000001
}
})
}
Processor (\_PR.CPU2, 0x02, 0x00000000, 0x00)
{
Name (_PSD, Package (0x01)
{
Package (0x05)
{
0x05,
0x00,
0x00000002,
0x000000FE,
0x00000001
}
})
}
Processor (\_PR.CPU3, 0x03, 0x00000000, 0x00)
{
Name (_PSD, Package (0x01)
{
Package (0x05)
{
0x05,
0x00,
0x00000003,
0x000000FE,
0x00000001
}
})
}
Change-Id: I5ef41b6ead4d88e9ba117003293dbc629c376803
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/48662
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
a011b5dca7