[PATCH 3.15 44/84] intel_pstate: Fix setting VID

Greg Kroah-Hartman
2014-07-15T23:38:51Z

From: Dirk Brandewie <dirk.j.brandewie@intel.com>

commit c16ed06024a6e699c332831dd50d8276744e3de8 upstream.

Commit 21855ff5 (intel_pstate: Set turbo VID for BayTrail) introduced
setting the turbo VID which is required to prevent a machine check on
some Baytrail SKUs under heavy graphics based workloads. The
docmumentation update that brought the requirement to light also
changed the bit mask used for enumerating P state and VID values from
0x7f to 0x3f.

This change returns the mask value to 0x7f.

Tested with the Intel NUC DN2820FYK,
BIOS version FYBYT10H.86A.0034.2014.0513.1413 with v3.16-rc1 and
v3.14.8 kernel versions.

Fixes: 21855ff5 (intel_pstate: Set turbo VID for BayTrail)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=77951
Reported-and-tested-by: Rune Reterson <rune@megahurts.dk>
Reported-and-tested-by: Eric Eickmeyer <erich@ericheickmeyer.com>
Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/cpufreq/intel_pstate.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -361,21 +361,21 @@ static int byt_get_min_pstate(void)
{
u64 value;
rdmsrl(BYT_RATIOS, value);
- return (value >> 8) & 0x3F;
+ return (value >> 8) & 0x7F;
}

static int byt_get_max_pstate(void)
{
u64 value;
rdmsrl(BYT_RATIOS, value);
- return (value >> 16) & 0x3F;
+ return (value >> 16) & 0x7F;
}

static int byt_get_turbo_pstate(void)
{
u64 value;
rdmsrl(BYT_TURBO_RATIOS, value);
- return value & 0x3F;
+ return value & 0x7F;
}

static void byt_set_pstate(struct cpudata *cpudata, int pstate)
@@ -409,8 +409,8 @@ static void byt_get_vid(struct cpudata *

rdmsrl(BYT_VIDS, value);
- cpudata->vid.min = int_tofp((value >> 8) & 0x3f);
- cpudata->vid.max = int_tofp((value >> 16) & 0x3f);
+ cpudata->vid.min = int_tofp((value >> 8) & 0x7f);
+ cpudata->vid.max = int_tofp((value >> 16) & 0x7f);
cpudata->vid.ratio = div_fp(
cpudata->vid.max - cpudata->vid.min,
int_tofp(cpudata->pstate.max_pstate -