[coreboot-gerrit] New patch to review for coreboot: f60d3f6 haswell: Put each logical processor in its own P-state domain

[Stefan Reinauer]

Stefan Reinauer ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/4130

-gerrit

commit f60d3f60309ad6e4e4990c6e86a4b4dba9f96e41
Author: Duncan Laurie 
Date:   Fri Apr 19 10:02:23 2013 -0700

haswell: Put each logical processor in its own P-state domain

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.

$ 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 
    Reviewed-on: https://gerrit.chromium.org/gerrit/48662
    Reviewed-by: Aaron Durbin 
---
 src/cpu/intel/haswell/acpi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/cpu/intel/haswell/acpi.c b/src/cpu/intel/haswell/acpi.c
index a4d9cd9..9e10c75 100644
--- a/src/cpu/intel/haswell/acpi.c
+++ b/src/cpu/intel/haswell/acpi.c
@@ -254,7 +254,7 @@ static int generate_P_state_entries(int core, int cores_per_package)
    len += acpigen_write_PPC_NVS();

/* Write PSD indicating configured coordination type */
-	len += acpigen_write_PSD_package(core, cores_per_package, coord_type);
+	len += acpigen_write_PSD_package(core, 1, coord_type);

/* Add P-state entries in _PSS table */
    len += acpigen_write_name("_PSS");
@@ -346,7 +346,7 @@ void generate_cpu_entries(void)

/* Generate P-state tables */
    		len_pr += generate_P_state_entries(
-				cpuID-1, cores_per_package);
+				coreID-1, cores_per_package);

/* Generate C-state tables */
    		len_pr += generate_C_state_entries();