Re: [PATCH v4 21/24] PM / devfreq: tegra30: Synchronize average count on target's update

Chanwoo Choi
2019-07-18T10:15:54Z

On 19. 7. 8. 오전 7:33, Dmitry Osipenko wrote:
> The average count may get out of sync if interrupt was disabled / avoided
> for a long time due to upper watermark optimization, hence it should be
> re-synced on each target's update to ensure that watermarks are set up
> correctly on EMC rate-change notification and that a correct frequency
> is selected for device.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/devfreq/tegra30-devfreq.c | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
> index 4d582809acb6..8a674fad26be 100644
> --- a/drivers/devfreq/tegra30-devfreq.c
> +++ b/drivers/devfreq/tegra30-devfreq.c
> @@ -466,11 +466,41 @@ static void actmon_isr_device(struct tegra_devfreq *tegra,
> dev->boost_freq, cpufreq_get(0));
> }
>
> +static void tegra_devfreq_sync_avg_count(struct tegra_devfreq *tegra,
> + struct tegra_devfreq_device *dev)
> +{
> + u32 avg_count, avg_freq, old_upper, new_upper;
> +
> + avg_count = device_readl(dev, ACTMON_DEV_AVG_COUNT);
> + avg_freq = avg_count / ACTMON_SAMPLING_PERIOD;
> +
> + old_upper = tegra_actmon_upper_freq(tegra, dev->avg_freq);
> + new_upper = tegra_actmon_upper_freq(tegra, avg_freq);
> +
> + /* similar to ISR, see comments in actmon_isr_device() */
> + if (old_upper != new_upper) {
> + dev->avg_freq = avg_freq;
> + dev->boost_freq = 0;
> + }
> +}
> +
> static unsigned long actmon_update_target(struct tegra_devfreq *tegra,
> struct tegra_devfreq_device *dev)
> {
> unsigned long target_freq;
>
> + /*
> + * The avg_count / avg_freq is getting snapshoted on device's
> + * interrupt, but there are cases where actual value need to
> + * be utilized on target's update, like CPUFreq boosting and
> + * overriding the min freq via /sys/class/devfreq/devfreq0/min_freq
> + * because we're optimizing the upper watermark based on the
> + * actual EMC frequency. This means that interrupt may be
> + * inactive for a long time and thus making snapshoted value
> + * outdated.
> + */
> + tegra_devfreq_sync_avg_count(tegra, dev);

I think that you don't need to add the separate function to calculate
the 'dev->avg_freq'. It is enough with your detailed comment to add
this code in this function.

> +
> target_freq = min(dev->avg_freq + dev->boost_freq, KHZ_MAX);
> target_freq = tegra_actmon_account_cpu_freq(tegra, dev, target_freq);
>
>

And also, is it impossible to squash this patch with patch19/patch20?

--
Best Regards,
Chanwoo Choi
Samsung Electronics