Re: [PATCH v4 05/24] PM / devfreq: tegra30: Set up watermarks properly

Chanwoo Choi
2019-07-19T01:28:20Z

On 19. 7. 19. 오전 9:00, Dmitry Osipenko wrote:
> В Thu, 18 Jul 2019 19:17:17 +0900
> Chanwoo Choi <cw00.choi@samsung.com> пишет:
>
>> On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote:
>>> The current implementation is inaccurate and results in very
>>> intensive interrupt activity, which neglects the whole idea of
>>> polling offload to hardware. The reason of the shortcoming is that
>>> watermarks are not set up correctly and this results in ACTMON
>>> constantly asking to change freq and then these requests are
>>> ignored. The end result of this patch is that there are few
>>> hundreds of ACTMON's interrupts instead of tens thousands after few
>>> minutes of a working devfreq, meanwhile the transitions activity
>>> stays about the same and governor becomes more reactive.
>>>
>>> Since watermarks are set precisely correct now, the boosting logic
>>> is changed a tad to accommodate the change. The "average sustain
>>> coefficient" multiplier is gone now since there is no need to
>>> compensate the improper watermarks and EMC frequency-bump happens
>>> once boosting hits the upper watermark enough times, depending on
>>> the per-device boosting threshold.
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>> ---
>>> drivers/devfreq/tegra30-devfreq.c | 293
>>> +++++++++++++++++++++--------- 1 file changed, 209 insertions(+),
>>> 84 deletions(-)
>>>
>>> diff --git a/drivers/devfreq/tegra30-devfreq.c
>>> b/drivers/devfreq/tegra30-devfreq.c index
>>> 4be7858c33bc..16f7e6cf3b99 100644 ---
>>> a/drivers/devfreq/tegra30-devfreq.c +++
>>> b/drivers/devfreq/tegra30-devfreq.c @@ -47,6 +47,8 @@
>>>
>>> #define ACTMON_DEV_INTR_CONSECUTIVE_UPPER
>>> BIT(31) #define
>>> ACTMON_DEV_INTR_CONSECUTIVE_LOWER BIT(30)
>>> +#define
>>> ACTMON_DEV_INTR_AVG_BELOW_WMARK
>>> BIT(25) +#define
>>> ACTMON_DEV_INTR_AVG_ABOVE_WMARK
>>> BIT(24) #define
>>> ACTMON_ABOVE_WMARK_WINDOW 1 #define
>>> ACTMON_BELOW_WMARK_WINDOW 3 @@ -63,9
>>> +65,8 @@
>>> * ACTMON_AVERAGE_WINDOW_LOG2: default value for @DEV_CTRL_K_VAL,
>>> which
>>> * translates to 2 ^ (K_VAL + 1). ex: 2 ^ (6 + 1) = 128
>>> */
>>> -#define ACTMON_AVERAGE_WINDOW_LOG2 6
>>> -#define ACTMON_SAMPLING_PERIOD
>>> 12 /* ms */ -#define
>>> ACTMON_DEFAULT_AVG_BAND 6 /* 1/10
>>> of % */ +#define
>>> ACTMON_AVERAGE_WINDOW_LOG2 6
>>> +#define
>>> ACTMON_SAMPLING_PERIOD 12 /*
>>> ms */ #define
>>> KHZ 1000 @@
>>> -142,9 +143,6 @@ struct tegra_devfreq_device {
>>> * watermark breaches.
>>> */
>>> unsigned long boost_freq;
>>> -
>>> - /* Optimal frequency calculated from the stats for this
>>> device */
>>> - unsigned long target_freq;
>>> };
>>>
>>> struct tegra_devfreq {
>>> @@ -156,7 +154,6 @@ struct tegra_devfreq {
>>>
>>> struct clk *emc_clock;
>>> unsigned long max_freq;
>>> - unsigned long cur_freq;
>>> struct notifier_block rate_change_nb;
>>>
>>> struct tegra_devfreq_device
>>> devices[ARRAY_SIZE(actmon_device_configs)]; @@ -205,42 +202,182 @@
>>> static unsigned long do_percent(unsigned long val, unsigned int
>>> pct) return val * pct / 100; }
>>>
>>> +static unsigned long actmon_cpu_to_emc_rate(struct tegra_devfreq
>>> *tegra) +{
>>> + struct tegra_actmon_emc_ratio *ratio = actmon_emc_ratios;
>>> + unsigned int cpu_freq = cpufreq_get(0);
>>> + unsigned int i;
>>> +
>>> + for (i = 0; i < ARRAY_SIZE(actmon_emc_ratios); i++,
>>> ratio++) {
>>> + if (cpu_freq >= ratio->cpu_freq) {
>>> + if (ratio->emc_freq >= tegra->max_freq)
>>> + return tegra->max_freq;
>>> + else
>>> + return ratio->emc_freq;
>>> + }
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static unsigned long
>>> +tegra_actmon_account_cpu_freq(struct tegra_devfreq *tegra,
>>> + struct tegra_devfreq_device *dev,
>>> + unsigned long target_freq)
>>> +{
>>> + unsigned long static_cpu_emc_freq;
>>> +
>>> + if (dev->config->avg_dependency_threshold &&
>>> + dev->config->avg_dependency_threshold <
>>> dev->avg_count) {
>>> + static_cpu_emc_freq =
>>> actmon_cpu_to_emc_rate(tegra);
>>> + target_freq = max(target_freq,
>>> static_cpu_emc_freq);
>>> + }
>>> +
>>> + return target_freq;
>>> +}
>>> +
>>> +static unsigned long tegra_actmon_lower_freq(struct tegra_devfreq
>>> *tegra,
>>> + unsigned long
>>> target_freq) +{
>>> + unsigned long lower = target_freq;
>>> + struct dev_pm_opp *opp;
>>> +
>>> + opp =
>>> dev_pm_opp_find_freq_floor(tegra->devfreq->dev.parent, &lower);
>>> + if (IS_ERR(opp))
>>> + lower = 0;
>>> + else
>>> + dev_pm_opp_put(opp);
>>> +
>>> + return lower;
>>> +}
>>> +
>>> +static unsigned long tegra_actmon_upper_freq(struct tegra_devfreq
>>> *tegra,
>>> + unsigned long
>>> target_freq) +{
>>> + unsigned long upper = target_freq + 1;
>>> + struct dev_pm_opp *opp;
>>> +
>>> + opp =
>>> dev_pm_opp_find_freq_ceil(tegra->devfreq->dev.parent, &upper);
>>> + if (IS_ERR(opp))
>>> + upper = ULONG_MAX;
>>> + else
>>> + dev_pm_opp_put(opp);
>>> +
>>> + return upper;
>>> +}
>>> +
>>> +static void tegra_actmon_get_lower_upper(struct tegra_devfreq
>>> *tegra,
>>> + struct
>>> tegra_devfreq_device *dev,
>>> + unsigned long target_freq,
>>> + unsigned long *lower,
>>> + unsigned long *upper)
>>> +{
>>> + /*
>>> + * Memory frequencies are guaranteed to have 1MHz
>>> granularity
>>> + * and thus we need this rounding down to get a proper
>>> watermarks
>>> + * range in a case where target_freq falls into a range of
>>> + * next_possible_opp_freq - 1MHz.
>>> + */
>>> + target_freq = round_down(target_freq, 1000000);
>>> +
>>> + /* watermarks are set at the borders of the corresponding
>>> OPPs */
>>> + *lower = tegra_actmon_lower_freq(tegra, target_freq);
>>> + *upper = tegra_actmon_upper_freq(tegra, target_freq);
>>> +
>>> + *lower /= KHZ;
>>> + *upper /= KHZ;
>>> +
>>> + /*
>>> + * The upper watermark should take into account CPU's
>>> frequency
>>> + * because cpu_to_emc_rate() may override the target_freq
>>> with
>>> + * a higher value and thus upper watermark need to be set
>>> up
>>> + * accordingly to avoid parasitic upper-events.
>>> + */
>>> + *upper = tegra_actmon_account_cpu_freq(tegra, dev, *upper);
>>> +
>>> + *lower *= ACTMON_SAMPLING_PERIOD;
>>> + *upper *= ACTMON_SAMPLING_PERIOD;
>>> +}
>>> +
>>> static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq
>>> *tegra, struct tegra_devfreq_device *dev)
>>> {
>>> - u32 avg = dev->avg_count;
>>> - u32 avg_band_freq = tegra->max_freq *
>>> ACTMON_DEFAULT_AVG_BAND / KHZ;
>>> - u32 band = avg_band_freq * ACTMON_SAMPLING_PERIOD;
>>> + unsigned long lower, upper, freq;
>>>
>>> - device_writel(dev, avg + band, ACTMON_DEV_AVG_UPPER_WMARK);
>>> + freq = dev->avg_count / ACTMON_SAMPLING_PERIOD * KHZ;
>>> + tegra_actmon_get_lower_upper(tegra, dev, freq, &lower,
>>> &upper);
>>> - avg = max(dev->avg_count, band);
>>> - device_writel(dev, avg - band, ACTMON_DEV_AVG_LOWER_WMARK);
>>> + /*
>>> + * We want to get interrupts when MCCPU client crosses the
>>> + * dependency threshold in order to take into / out of
>>> account
>>> + * the CPU's freq.
>>> + */
>>> + if (lower < dev->config->avg_dependency_threshold &&
>>> + upper > dev->config->avg_dependency_threshold) {
>>> + if (dev->avg_count <
>>> dev->config->avg_dependency_threshold)
>>> + upper =
>>> dev->config->avg_dependency_threshold;
>>> + else
>>> + lower =
>>> dev->config->avg_dependency_threshold;
>>> + }
>>> +
>>> + device_writel(dev, lower, ACTMON_DEV_AVG_LOWER_WMARK);
>>> + device_writel(dev, upper, ACTMON_DEV_AVG_UPPER_WMARK);
>>> }
>>>
>>> static void tegra_devfreq_update_wmark(struct tegra_devfreq *tegra,
>>> - struct tegra_devfreq_device
>>> *dev)
>>> + struct tegra_devfreq_device
>>> *dev,
>>> + unsigned long freq)
>>> {
>>> - u32 val = tegra->cur_freq * ACTMON_SAMPLING_PERIOD;
>>> + unsigned long lower, upper, delta;
>>> +
>>> + /*
>>> + * Boosting logic kicks-in once lower / upper watermark is
>>> hit.
>>> + * The watermarks are based on the updated EMC rate and the
>>> + * average activity.
>>> + *
>>> + * The higher watermark is set in accordance to the EMC
>>> rate
>>> + * because we want to set it to the highest mark here and
>>> EMC rate
>>> + * represents that mark. The consecutive-upper interrupts
>>> are
>>> + * always enabled and we don't want to receive them if
>>> they won't
>>> + * do anything useful, hence the upper watermark is capped
>>> to maximum.
>>> + * Note that the EMC rate is changed once boosting pushed
>>> the rate
>>> + * too high, in that case boosting-up will be stopped
>>> because
>>> + * upper watermark is much higher now and it is
>>> *important* to
>>> + * stop the unwanted interrupts.
>>> + */
>>> + tegra_actmon_get_lower_upper(tegra, dev, freq - 1, &lower,
>>> &upper); +
>>> + delta = do_percent(upper - lower,
>>> dev->config->boost_up_threshold);
>>> + device_writel(dev, lower + delta, ACTMON_DEV_UPPER_WMARK);
>>>
>>> - device_writel(dev, do_percent(val,
>>> dev->config->boost_up_threshold),
>>> - ACTMON_DEV_UPPER_WMARK);
>>> + /*
>>> + * Meanwhile the lower mark is based on the average value
>>> + * because it is the lowest possible consecutive-mark for
>>> this
>>> + * device. Once that mark is hit and boosting is stopped,
>>> the
>>> + * interrupt is disabled by ISR.
>>> + */
>>> + freq = dev->avg_count / ACTMON_SAMPLING_PERIOD * KHZ;
>>> + tegra_actmon_get_lower_upper(tegra, dev, freq, &lower,
>>> &upper);
>>> - device_writel(dev, do_percent(val,
>>> dev->config->boost_down_threshold),
>>> - ACTMON_DEV_LOWER_WMARK);
>>> + delta = do_percent(upper - lower,
>>> dev->config->boost_down_threshold);
>>> + device_writel(dev, lower + delta, ACTMON_DEV_LOWER_WMARK);
>>> }
>>>
>>> static void actmon_isr_device(struct tegra_devfreq *tegra,
>>> struct tegra_devfreq_device *dev)
>>> {
>>> - u32 intr_status, dev_ctrl;
>>> + u32 intr_status, dev_ctrl, avg_intr_mask;
>>>
>>> dev->avg_count = device_readl(dev, ACTMON_DEV_AVG_COUNT);
>>> - tegra_devfreq_update_avg_wmark(tegra, dev);
>>> -
>>> intr_status = device_readl(dev, ACTMON_DEV_INTR_STATUS);
>>> dev_ctrl = device_readl(dev, ACTMON_DEV_CTRL);
>>>
>>> + avg_intr_mask = ACTMON_DEV_INTR_AVG_BELOW_WMARK |
>>> + ACTMON_DEV_INTR_AVG_ABOVE_WMARK;
>>> +
>>> + if (intr_status & avg_intr_mask)
>>> + tegra_devfreq_update_avg_wmark(tegra, dev);
>>> +
>>> if (intr_status & ACTMON_DEV_INTR_CONSECUTIVE_UPPER) {
>>> /*
>>> * new_boost = min(old_boost * up_coef + step,
>>> max_freq) @@ -253,8 +390,6 @@ static void actmon_isr_device(struct
>>> tegra_devfreq *tegra,
>>> if (dev->boost_freq >= tegra->max_freq)
>>> dev->boost_freq = tegra->max_freq;
>>> - else
>>> - dev_ctrl |=
>>> ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN; } else if (intr_status
>>> & ACTMON_DEV_INTR_CONSECUTIVE_LOWER) { /*
>>> * new_boost = old_boost * down_coef
>>> @@ -263,63 +398,37 @@ static void actmon_isr_device(struct
>>> tegra_devfreq *tegra, dev->boost_freq = do_percent(dev->boost_freq,
>>> dev->config->boost_down_coeff);
>>>
>>> - dev_ctrl |=
>>> ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN; -
>>> if (dev->boost_freq < (ACTMON_BOOST_FREQ_STEP >>
>>> 1)) dev->boost_freq = 0;
>>> - else
>>> - dev_ctrl |=
>>> ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN; }
>>>
>>> - if (dev->config->avg_dependency_threshold) {
>>> - if (dev->avg_count >=
>>> dev->config->avg_dependency_threshold)
>>> - dev_ctrl |=
>>> ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
>>> - else if (dev->boost_freq == 0)
>>> - dev_ctrl &=
>>> ~ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
>>> + if (intr_status & avg_intr_mask) {
>>> + /*
>>> + * Once average watermark is hit, it means that
>>> the memory
>>> + * activity changed significantly and thus
>>> boosting-up shall
>>> + * be reset because EMC clock rate will be changed
>>> and
>>> + * boosting will restart in this case.
>>> + */
>>> + dev->boost_freq = 0;
>>> }
>>>
>>> - device_writel(dev, dev_ctrl, ACTMON_DEV_CTRL);
>>> + /* no boosting => no need for consecutive-down interrupt */
>>> + if (dev->boost_freq == 0)
>>> + dev_ctrl &=
>>> ~ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
>>> + device_writel(dev, dev_ctrl, ACTMON_DEV_CTRL);
>>> device_writel(dev, ACTMON_INTR_STATUS_CLEAR,
>>> ACTMON_DEV_INTR_STATUS); }
>>>
>>> -static unsigned long actmon_cpu_to_emc_rate(struct tegra_devfreq
>>> *tegra,
>>> - unsigned long cpu_freq)
>>> -{
>>> - unsigned int i;
>>> - struct tegra_actmon_emc_ratio *ratio = actmon_emc_ratios;
>>> -
>>> - for (i = 0; i < ARRAY_SIZE(actmon_emc_ratios); i++,
>>> ratio++) {
>>> - if (cpu_freq >= ratio->cpu_freq) {
>>> - if (ratio->emc_freq >= tegra->max_freq)
>>> - return tegra->max_freq;
>>> - else
>>> - return ratio->emc_freq;
>>> - }
>>> - }
>>> -
>>> - return 0;
>>> -}
>>> -
>>> -static void actmon_update_target(struct tegra_devfreq *tegra,
>>> - struct tegra_devfreq_device *dev)
>>> +static unsigned long actmon_update_target(struct tegra_devfreq
>>> *tegra,
>>> + struct
>>> tegra_devfreq_device *dev) {
>>> - unsigned long cpu_freq = 0;
>>> - unsigned long static_cpu_emc_freq = 0;
>>> - unsigned int avg_sustain_coef;
>>> -
>>> - if (dev->config->avg_dependency_threshold) {
>>> - cpu_freq = cpufreq_get(0);
>>> - static_cpu_emc_freq =
>>> actmon_cpu_to_emc_rate(tegra, cpu_freq);
>>> - }
>>> + unsigned long target_freq;
>>>
>>> - dev->target_freq = dev->avg_count / ACTMON_SAMPLING_PERIOD;
>>> - avg_sustain_coef = 100 * 100 /
>>> dev->config->boost_up_threshold;
>>> - dev->target_freq = do_percent(dev->target_freq,
>>> avg_sustain_coef);
>>> - dev->target_freq += dev->boost_freq;
>>> + target_freq = dev->avg_count / ACTMON_SAMPLING_PERIOD +
>>> dev->boost_freq;
>>> + target_freq = tegra_actmon_account_cpu_freq(tegra, dev,
>>> target_freq);
>>> - if (dev->avg_count >=
>>> dev->config->avg_dependency_threshold)
>>> - dev->target_freq = max(dev->target_freq,
>>> static_cpu_emc_freq);
>>> + return target_freq;
>>> }
>>>
>>> static irqreturn_t actmon_thread_isr(int irq, void *data)
>>> @@ -351,8 +460,8 @@ static int tegra_actmon_rate_notify_cb(struct
>>> notifier_block *nb, unsigned long action, void *ptr)
>>> {
>>> struct clk_notifier_data *data = ptr;
>>> - struct tegra_devfreq *tegra;
>>> struct tegra_devfreq_device *dev;
>>> + struct tegra_devfreq *tegra;
>>> unsigned int i;
>>>
>>> if (action != POST_RATE_CHANGE)
>>> @@ -360,12 +469,28 @@ static int tegra_actmon_rate_notify_cb(struct
>>> notifier_block *nb,
>>> tegra = container_of(nb, struct tegra_devfreq,
>>> rate_change_nb);
>>> - tegra->cur_freq = data->new_rate / KHZ;
>>> -
>>> + /*
>>> + * EMC rate could change due to three reasons:
>>> + *
>>> + * 1. Average watermark hit
>>> + * 2. Boosting overflow
>>> + * 3. CPU freq change
>>> + *
>>> + * Once rate is changed, the consecutive watermarks need
>>> to be
>>> + * updated in order for boosting to work properly and to
>>> avoid
>>> + * unnecessary interrupts. Note that the consecutive range
>>> is set for
>>> + * all of devices using the same rate, hence if CPU is
>>> doing much
>>> + * less than the other memory clients, then its upper
>>> watermark will
>>> + * be very high in comparison to the actual activity
>>> (lower watermark)
>>> + * and thus unnecessary upper-interrupts will be
>>> suppressed.
>>> + *
>>> + * The average watermarks also should be updated because
>>> of 3.
>>> + */
>>> for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
>>> dev = &tegra->devices[i];
>>>
>>> - tegra_devfreq_update_wmark(tegra, dev);
>>> + tegra_devfreq_update_avg_wmark(tegra, dev);
>>> + tegra_devfreq_update_wmark(tegra, dev,
>>> data->new_rate); }
>>>
>>> return NOTIFY_OK;
>>> @@ -374,15 +499,14 @@ static int tegra_actmon_rate_notify_cb(struct
>>> notifier_block *nb, static void
>>> tegra_actmon_configure_device(struct tegra_devfreq *tegra, struct
>>> tegra_devfreq_device *dev) {
>>> - u32 val = 0;
>>> -
>>> - dev->target_freq = tegra->cur_freq;
>>> + u32 val = 0, target_freq;
>>>
>>> - dev->avg_count = tegra->cur_freq * ACTMON_SAMPLING_PERIOD;
>>> + target_freq = clk_get_rate(tegra->emc_clock) / KHZ;
>>> + dev->avg_count = target_freq * ACTMON_SAMPLING_PERIOD;
>>> device_writel(dev, dev->avg_count, ACTMON_DEV_INIT_AVG);
>>>
>>> tegra_devfreq_update_avg_wmark(tegra, dev);
>>> - tegra_devfreq_update_wmark(tegra, dev);
>>> + tegra_devfreq_update_wmark(tegra, dev, target_freq);
>>>
>>> device_writel(dev, ACTMON_COUNT_WEIGHT,
>>> ACTMON_DEV_COUNT_WEIGHT); device_writel(dev,
>>> ACTMON_INTR_STATUS_CLEAR, ACTMON_DEV_INTR_STATUS); @@ -469,13
>>> +593,13 @@ static int tegra_devfreq_get_dev_status(struct device
>>> *dev, struct tegra_devfreq_device *actmon_dev; unsigned long
>>> cur_freq;
>>> - cur_freq = READ_ONCE(tegra->cur_freq);
>>> + cur_freq = clk_get_rate(tegra->emc_clock);
>>>
>>> /* To be used by the tegra governor */
>>> stat->private_data = tegra;
>>>
>>> /* The below are to be used by the other governors */
>>> - stat->current_frequency = cur_freq * KHZ;
>>> + stat->current_frequency = cur_freq;
>>>
>>> actmon_dev = &tegra->devices[MCALL];
>>>
>>> @@ -486,7 +610,7 @@ static int tegra_devfreq_get_dev_status(struct
>>> device *dev, stat->busy_time *= 100 / BUS_SATURATION_RATIO;
>>>
>>> /* Number of cycles in a sampling period */
>>> - stat->total_time = ACTMON_SAMPLING_PERIOD * cur_freq;
>>> + stat->total_time = cur_freq / KHZ * ACTMON_SAMPLING_PERIOD;
>>>
>>> stat->busy_time = min(stat->busy_time, stat->total_time);
>>>
>>> @@ -505,6 +629,7 @@ static int tegra_governor_get_target(struct
>>> devfreq *devfreq, struct devfreq_dev_status *stat;
>>> struct tegra_devfreq *tegra;
>>> struct tegra_devfreq_device *dev;
>>> + unsigned long dev_target_freq;
>>> unsigned long target_freq = 0;
>>> unsigned int i;
>>> int err;
>>> @@ -520,9 +645,9 @@ static int tegra_governor_get_target(struct
>>> devfreq *devfreq, for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
>>> dev = &tegra->devices[i];
>>>
>>> - actmon_update_target(tegra, dev);
>>> + dev_target_freq = actmon_update_target(tegra, dev);
>>>
>>> - target_freq = max(target_freq, dev->target_freq);
>>> + target_freq = max(target_freq, dev_target_freq);
>>> }
>>>
>>> *freq = target_freq * KHZ;
>>> @@ -642,7 +767,6 @@ static int tegra_devfreq_probe(struct
>>> platform_device *pdev) return rate;
>>> }
>>>
>>> - tegra->cur_freq = clk_get_rate(tegra->emc_clock) / KHZ;
>>> tegra->max_freq = rate / KHZ;
>>>
>>> for (i = 0; i < ARRAY_SIZE(actmon_device_configs); i++) {
>>> @@ -671,7 +795,8 @@ static int tegra_devfreq_probe(struct
>>> platform_device *pdev) platform_set_drvdata(pdev, tegra);
>>>
>>> tegra->rate_change_nb.notifier_call =
>>> tegra_actmon_rate_notify_cb;
>>> - err = clk_notifier_register(tegra->emc_clock,
>>> &tegra->rate_change_nb);
>>> + err = clk_notifier_register(tegra->emc_clock,
>>> + &tegra->rate_change_nb);
>>> if (err) {
>>> dev_err(&pdev->dev,
>>> "Failed to register rate change
>>> notifier\n");
>>
>>
>> Maybe, it is possible to merge patch4/patch19/patch20 to one patch.
>
> All these three patches are completely separate changes, thus they
> should be kept separate.
>

I replied on patch19 why it is possible to merge patch5 and patch19.
Please check my comment.

--
Best Regards,
Chanwoo Choi
Samsung Electronics