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PM / devfreq: Rewrite devfreq_update_status() to fix multiple bugs 

The current devfreq_update_status() has the following bugs:
- If previous frequency doesn't have a valid level, it does an out of bounds
  access into the trans_table and causes memory corruption.
- When the new frequency doesn't have a valid level, the time spent in the
  new frequency is counted towards the next valid frequency switch instead of
  being ignored.
- The time spent on the previous frequency is added to the new frequency's
  stats instead of the previous frequency's stats.

This patch fixes all of this.

Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
This commit is contained in:
Saravana Kannan 2014-02-27 19:38:57 -08:00 committed by MyungJoo Ham
parent dcb99fd9b0
commit e35d35a1c0
1 changed files with 20 additions and 11 deletions
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31
drivers/devfreq/devfreq.c
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@ -91,26 +91,35 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
*/
static int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
{
int lev, prev_lev;
int lev, prev_lev, ret = 0;
unsigned long cur_time;
lev = devfreq_get_freq_level(devfreq, freq);
if (lev < 0)
return lev;
cur_time = jiffies;
devfreq->time_in_state[lev] +=
prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
if (prev_lev < 0) {
ret = prev_lev;
goto out;
}
devfreq->time_in_state[prev_lev] +=
cur_time - devfreq->last_stat_updated;
if (freq != devfreq->previous_freq) {
prev_lev = devfreq_get_freq_level(devfreq,
devfreq->previous_freq);
lev = devfreq_get_freq_level(devfreq, freq);
if (lev < 0) {
ret = lev;
goto out;
}
if (lev != prev_lev) {
devfreq->trans_table[(prev_lev *
devfreq->profile->max_state) + lev]++;
devfreq->total_trans++;
}
devfreq->last_stat_updated = cur_time;
return 0;
out:
devfreq->last_stat_updated = cur_time;
return ret;
}
/**