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authorDirk Brandewie <dirk.j.brandewie@intel.com>2014-10-13 19:37:44 +0400
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-10-24 01:00:00 +0400
commitd022a65ed2473fac4a600e3424503dc571160a3e (patch)
tree6ff152f13f0ce8918e97ecd968fd7d3fabf13fcf /drivers
parentb27580b05e6f5253228debc60b8ff4a786ff573a (diff)
downloadlinux-d022a65ed2473fac4a600e3424503dc571160a3e.tar.xz
intel_pstate: Correct BYT VID values.
Using a VID value that is not high enough for the requested P state can cause machine checks. Add a ceiling function to ensure calulated VIDs with fractional values are set to the next highest integer VID value. The algorythm for calculating the non-trubo VID from the BIOS writers guide is: vid_ratio = (vid_max - vid_min) / (max_pstate - min_pstate) vid = ceiling(vid_min + (req_pstate - min_pstate) * vid_ratio) Cc: All applicable <stable@vger.kernel.org> Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/cpufreq/intel_pstate.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 98593e0344c5..27bb6d3877ed 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -52,6 +52,17 @@ static inline int32_t div_fp(int32_t x, int32_t y)
return div_s64((int64_t)x << FRAC_BITS, y);
}
+static inline int ceiling_fp(int32_t x)
+{
+ int mask, ret;
+
+ ret = fp_toint(x);
+ mask = (1 << FRAC_BITS) - 1;
+ if (x & mask)
+ ret += 1;
+ return ret;
+}
+
struct sample {
int32_t core_pct_busy;
u64 aperf;
@@ -425,7 +436,7 @@ static void byt_set_pstate(struct cpudata *cpudata, int pstate)
cpudata->vid.ratio);
vid_fp = clamp_t(int32_t, vid_fp, cpudata->vid.min, cpudata->vid.max);
- vid = fp_toint(vid_fp);
+ vid = ceiling_fp(vid_fp);
if (pstate > cpudata->pstate.max_pstate)
vid = cpudata->vid.turbo;