diff options
| author | Dirk Brandewie <dirk.j.brandewie@intel.com> | 2014-10-13 08:37:44 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-11-14 09:00:01 -0800 |
| commit | 4b019cc1ad058c1378563b8fefb3da63d2f56ec6 (patch) | |
| tree | d7d102ec25cef59b134ea2815ec4e975ecb80341 | |
| parent | da0b49e81e0cb492b384db389c40bff9cbb2b179 (diff) | |
intel_pstate: Correct BYT VID values.
commit d022a65ed2473fac4a600e3424503dc571160a3e upstream.
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)
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>
| -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 ecd8310fbbae..533a509439ca 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -55,6 +55,17 @@ static inline int32_t div_fp(int32_t x, int32_t y) return div_s64((int64_t)x << FRAC_BITS, (int64_t)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; @@ -399,7 +410,7 @@ 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; |