leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

intel_pstate: Correct BYT VID values.

Browse Source 
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>
This commit is contained in:
Dirk Brandewie 2014-10-13 08:37:44 -07:00 committed by Rafael J. Wysocki
parent b27580b05e
commit d022a65ed2
1 changed files with 12 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/cpufreq/intel_pstate.c
View File

@ -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;