This is a note to let you know that I've just added the patch titled
intel_pstate: Correct BYT VID values.
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
intel_pstate-correct-byt-vid-values.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d022a65ed2473fac4a600e3424503dc571160a3e Mon Sep 17 00:00:00 2001
From: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>
Date: Mon, 13 Oct 2014 08:37:44 -0700
Subject: intel_pstate: Correct BYT VID values.
From: Dirk Brandewie <dirk.j.brandewie@xxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/cpufreq/intel_pstate.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
--- 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,
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 cpudat
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;
Patches currently in stable-queue which might be from dirk.j.brandewie@xxxxxxxxx are
queue-3.14/intel_pstate-fix-byt-frequency-reporting.patch
queue-3.14/cpufreq-expose-scaling_cur_freq-sysfs-file-for-set_policy-drivers.patch
queue-3.14/cpufreq-intel_pstate-fix-setting-max_perf_pct-in-performance-policy.patch
queue-3.14/cpufreq-intel_pstate-add-cpu-id-for-braswell-processor.patch
queue-3.14/intel_pstate-add-cpu-ids-for-broadwell-processors.patch
queue-3.14/intel_pstate-correct-byt-vid-values.patch
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