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

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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>
This commit is contained in:
Duncan Laurie 2013-04-19 10:02:23 -07:00 • committed by ChromeBot
commit a011b5dca7
1 changed files with 2 additions and 2 deletions
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4
src/cpu/intel/haswell/acpi.c
View file

@ -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();