diff options
| author | Dirk Brandewie <dirk.j.brandewie@intel.com> | 2014-10-13 08:37:44 -0700 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2014-10-23 23:00:00 +0200 |
| commit | d022a65ed2473fac4a600e3424503dc571160a3e (patch) | |
| tree | 6ff152f13f0ce8918e97ecd968fd7d3fabf13fcf | |
| parent | b27580b05e6f5253228debc60b8ff4a786ff573a (diff) | |
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>
| -rw-r--r-- | drivers/cpufreq/intel_pstate.c | 13 |
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; |