In the current code, if we fail during a frequency transition we simply send the
POSTCHANGE notification with old frequency. This isn't enough.
One of the core user of these notifications is the code responsible for keeping
loops_per_jiffy aligned with frequency change. And mostly it is written as:
if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
(val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
update-loops-per-jiffy...
}
So, suppose we are changing to a higher frequency and failed during transition,
then following will happen:
- CPUFREQ_PRECHANGE notification with freq-new > freq-old
- CPUFREQ_POSTCHANGE notification with freq-new == freq-old
The first one will update loops_per_jiffy and second one will do nothing. Even
if we send the 2nd notification by exchanging values of freq-new and old, some
users of these notifications might get unstable.
This can be fixed by simply calling cpufreq_notify_post_transition() with error
code and this routine will take care of sending notifications in correct order.
Signed-off-by: Viresh Kumar <viresh.ku...@linaro.org>
---
drivers/cpufreq/powernow-k8.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
index 0023c7d..e10b646 100644
--- a/drivers/cpufreq/powernow-k8.c
+++ b/drivers/cpufreq/powernow-k8.c
@@ -964,14 +964,9 @@ static int transition_frequency_fidvid(struct
powernow_k8_data *data,
cpufreq_cpu_put(policy);
cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
-
res = transition_fid_vid(data, fid, vid);
- if (res)
- freqs.new = freqs.old;
- else
- freqs.new = find_khz_freq_from_fid(data->currfid);
+ cpufreq_notify_post_transition(policy, &freqs, res);
- cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
return res;
}
--
1.7.12.rc2.18.g61b472e
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