Hello Chanwoo, 20.08.2019 3:23, Chanwoo Choi пишет: > On 19. 8. 12. 오전 6:23, Dmitry Osipenko wrote: >> We already had few integer overflow bugs, let's limit the freq for >> consistency. >> >> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx> >> --- >> drivers/devfreq/tegra30-devfreq.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c >> index 70dce58212a4..ca499368ee81 100644 >> --- a/drivers/devfreq/tegra30-devfreq.c >> +++ b/drivers/devfreq/tegra30-devfreq.c >> @@ -430,7 +430,7 @@ static unsigned long actmon_update_target(struct tegra_devfreq *tegra, >> target_freq = dev->avg_count / ACTMON_SAMPLING_PERIOD + dev->boost_freq; >> target_freq = tegra_actmon_account_cpu_freq(tegra, dev, target_freq); >> >> - return target_freq; >> + return min(target_freq, tegra->max_freq); > > Once again, did you meet this case sometimes? This case happens at least whenever CPU's freq accounting returns KHZ_MAX, please see actmon_emc_ratios[] and actmon_cpu_to_emc_rate(). > Usually, we can prevent the overflow of target_freq > when calculating the target frequency or this style. > > I think that if the overflow of target frequency happen frequently, > it might have the problem of calculation way. It is possible to get sampled avg_count from hardware that results in target_freq > max_freq because translating number of memory events to memory frequency has some calculation error, although it is negligible. In fact, it shouldn't matter that the returned target_freq > max_freq with the current driver's code structure and in the commit's message I wrote that this change is done for consistency. Hence it should be okay to drop this patch as well.
