Date:   Thu, 14 Nov 2019 10:52:04 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Kamil Konieczny <k.konieczny@...sung.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Kamil Konieczny <k.konieczny@...tner.samsung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
Subject: Re: [PATCH 7/7] devfreq: move statistics to separate struct

Hi Kamil,

The 'freq_table' and 'max_state' in the devfreq_dev_profile
were used in the ARM Mali device driver[1][2][3]. Although ARM Mali
device driver was posted to mainline kernel, they used
them for a long time. It means that this patch break
the compatibility. The ARM Mali drivers are very
important devfreq device driver. 

[1] https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-drivers/bifrost-kernel#
[2] https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-drivers/midgard-kernel
[3] https://developer.arm.com/tools-and-software/graphics-and-gaming/mali-drivers/utgard-kernel

Also, the devfreq device driver specifies their own
information and data into devfreq_dev_profile structure 
before registering the devfreq device with devfreq_add_device().
This patch breaks the basic usage rule of devfreq_dev_profile structure.

So, I can't agree this patch. Not ack.

Regards,
Chanwoo Choi

On 11/13/19 6:13 PM, Kamil Konieczny wrote:
> Count time and transitions between devfreq frequencies in separate struct
> for improved code readability and maintenance.
> 
> Signed-off-by: Kamil Konieczny <k.konieczny@...sung.com>
> ---
>  drivers/devfreq/devfreq.c          | 156 ++++++++++++++++-------------
>  drivers/devfreq/exynos-bus.c       |   6 +-
>  drivers/devfreq/governor_passive.c |  26 +++--
>  include/linux/devfreq.h            |  43 ++++----
>  4 files changed, 129 insertions(+), 102 deletions(-)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index d79412b0de59..d85867a91230 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -105,10 +105,11 @@ static unsigned long find_available_max_freq(struct devfreq *devfreq)
>   */
>  static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>  {
> +	struct devfreq_stats *stats = devfreq->profile->stats;
>  	int lev;
>  
> -	for (lev = 0; lev < devfreq->profile->max_state; lev++)
> -		if (freq == devfreq->profile->freq_table[lev])
> +	for (lev = 0; lev < stats->max_state; lev++)
> +		if (freq == stats->freq_table[lev])
>  			return lev;
>  
>  	return -EINVAL;
> @@ -117,56 +118,64 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
>  static int set_freq_table(struct devfreq *devfreq)
>  {
>  	struct devfreq_dev_profile *profile = devfreq->profile;
> +	struct devfreq_stats *stats;
>  	struct dev_pm_opp *opp;
>  	unsigned long freq;
> -	int i, count;
> +	int i, count, err = -ENOMEM;
>  
>  	/* Initialize the freq_table from OPP table */
>  	count = dev_pm_opp_get_opp_count(devfreq->dev.parent);
>  	if (count <= 0)
>  		return -EINVAL;
>  
> -	profile->max_state = count;
> -	profile->freq_table = devm_kcalloc(devfreq->dev.parent,
> -					count,
> -					sizeof(*profile->freq_table),
> -					GFP_KERNEL);
> -	if (!profile->freq_table) {
> -		profile->max_state = 0;
> +	stats = devm_kzalloc(devfreq->dev.parent,
> +			     sizeof(struct devfreq_stats), GFP_KERNEL);
> +	if (!stats)
>  		return -ENOMEM;
> -	}
>  
> -	for (i = 0, freq = 0; i < profile->max_state; i++, freq++) {
> +	profile->stats = stats;
> +	stats->max_state = count;
> +	stats->freq_table = devm_kcalloc(devfreq->dev.parent,
> +					 count,
> +					 sizeof(*stats->freq_table),
> +					 GFP_KERNEL);
> +	if (!stats->freq_table)
> +		goto err_no_mem;
> +
> +	for (i = 0, freq = 0; i < count; i++, freq++) {
>  		opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
>  		if (IS_ERR(opp)) {
> -			devm_kfree(devfreq->dev.parent, profile->freq_table);
> -			profile->max_state = 0;
> -			return PTR_ERR(opp);
> +			devm_kfree(devfreq->dev.parent, stats->freq_table);
> +			stats->max_state = 0;
> +			err = PTR_ERR(opp);
> +			goto err_no_mem;
>  		}
>  		dev_pm_opp_put(opp);
> -		profile->freq_table[i] = freq;
> +		stats->freq_table[i] = freq;
>  	}
>  
> -	profile->trans_table = devm_kzalloc(devfreq->dev.parent,
> -					    array3_size(sizeof(unsigned int),
> -							count, count),
> -					    GFP_KERNEL);
> -	if (!profile->trans_table)
> +	stats->trans_table = devm_kzalloc(devfreq->dev.parent,
> +					  array3_size(sizeof(unsigned int),
> +						      count, count),
> +					  GFP_KERNEL);
> +	if (!stats->trans_table)
>  		goto err_no_mem;
>  
> -	profile->time_in_state = devm_kcalloc(devfreq->dev.parent, count,
> -					      sizeof(*profile->time_in_state),
> -					      GFP_KERNEL);
> -	if (!profile->time_in_state)
> +	stats->time_in_state = devm_kcalloc(devfreq->dev.parent, count,
> +					    sizeof(*stats->time_in_state),
> +					    GFP_KERNEL);
> +	if (!stats->time_in_state)
>  		goto err_no_mem;
>  
> -	profile->last_time = get_jiffies_64();
> -	spin_lock_init(&profile->stats_lock);
> +	stats->last_time = get_jiffies_64();
> +	spin_lock_init(&stats->stats_lock);
>  
>  	return 0;
>  err_no_mem:
> -	profile->max_state = 0;
> -	return -ENOMEM;
> +	stats->max_state = 0;
> +	devm_kfree(devfreq->dev.parent, profile->stats);
> +	profile->stats = NULL;
> +	return err;
>  }
>  
>  /**
> @@ -176,7 +185,7 @@ static int set_freq_table(struct devfreq *devfreq)
>   */
>  int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>  {
> -	struct devfreq_dev_profile *profile = devfreq->profile;
> +	struct devfreq_stats *stats = devfreq->profile->stats;
>  	unsigned long long cur_time;
>  	int lev, prev_lev, ret = 0;
>  
> @@ -184,22 +193,21 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>  
>  	/* Immediately exit if previous_freq is not initialized yet. */
>  	if (!devfreq->previous_freq) {
> -		spin_lock(&profile->stats_lock);
> -		profile->last_time = cur_time;
> -		spin_unlock(&profile->stats_lock);
> +		spin_lock(&stats->stats_lock);
> +		stats->last_time = cur_time;
> +		spin_unlock(&stats->stats_lock);
>  		return 0;
>  	}
>  
>  	prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
>  
> -	spin_lock(&profile->stats_lock);
> +	spin_lock(&stats->stats_lock);
>  	if (prev_lev < 0) {
>  		ret = prev_lev;
>  		goto out;
>  	}
>  
> -	profile->time_in_state[prev_lev] +=
> -			 cur_time - profile->last_time;
> +	stats->time_in_state[prev_lev] += cur_time - stats->last_time;
>  	lev = devfreq_get_freq_level(devfreq, freq);
>  	if (lev < 0) {
>  		ret = lev;
> @@ -207,14 +215,14 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
>  	}
>  
>  	if (lev != prev_lev) {
> -		profile->trans_table[(prev_lev *
> -				profile->max_state) + lev]++;
> -		profile->total_trans++;
> +		stats->trans_table[(prev_lev *
> +				stats->max_state) + lev]++;
> +		stats->total_trans++;
>  	}
>  
>  out:
> -	profile->last_time = cur_time;
> -	spin_unlock(&profile->stats_lock);
> +	stats->last_time = cur_time;
> +	spin_unlock(&stats->stats_lock);
>  	return ret;
>  }
>  EXPORT_SYMBOL(devfreq_update_status);
> @@ -504,9 +512,9 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
>  		queue_delayed_work(devfreq_wq, &devfreq->work,
>  			msecs_to_jiffies(profile->polling_ms));
>  
> -	spin_lock(&profile->stats_lock);
> -	profile->last_time = get_jiffies_64();
> -	spin_unlock(&profile->stats_lock);
> +	spin_lock(&profile->stats->stats_lock);
> +	profile->stats->last_time = get_jiffies_64();
> +	spin_unlock(&profile->stats->stats_lock);
>  	devfreq->stop_polling = false;
>  
>  	if (profile->get_cur_freq &&
> @@ -677,7 +685,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
>  	devfreq->data = data;
>  	devfreq->nb.notifier_call = devfreq_notifier_call;
>  
> -	if (!profile->max_state && !profile->freq_table) {
> +	if (!profile->stats) {
>  		mutex_unlock(&devfreq->lock);
>  		err = set_freq_table(devfreq);
>  		if (err < 0)
> @@ -1282,6 +1290,7 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
>  			      const char *buf, size_t count)
>  {
>  	struct devfreq *df = to_devfreq(dev);
> +	struct devfreq_stats *stats = df->profile->stats;
>  	unsigned long value;
>  	int ret;
>  
> @@ -1297,13 +1306,13 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
>  			goto unlock;
>  		}
>  	} else {
> -		unsigned long *freq_table = df->profile->freq_table;
> +		unsigned long *freq_table = stats->freq_table;
>  
>  		/* Get minimum frequency according to sorting order */
> -		if (freq_table[0] < freq_table[df->profile->max_state - 1])
> +		if (freq_table[0] < freq_table[stats->max_state - 1])
>  			value = freq_table[0];
>  		else
> -			value = freq_table[df->profile->max_state - 1];
> +			value = freq_table[stats->max_state - 1];
>  	}
>  
>  	df->min_freq = value;
> @@ -1326,6 +1335,7 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
>  			      const char *buf, size_t count)
>  {
>  	struct devfreq *df = to_devfreq(dev);
> +	struct devfreq_stats *stats = df->profile->stats;
>  	unsigned long value;
>  	int ret;
>  
> @@ -1341,11 +1351,11 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
>  			goto unlock;
>  		}
>  	} else {
> -		unsigned long *freq_table = df->profile->freq_table;
> +		unsigned long *freq_table = stats->freq_table;
>  
>  		/* Get maximum frequency according to sorting order */
> -		if (freq_table[0] < freq_table[df->profile->max_state - 1])
> -			value = freq_table[df->profile->max_state - 1];
> +		if (freq_table[0] < freq_table[stats->max_state - 1])
> +			value = freq_table[stats->max_state - 1];
>  		else
>  			value = freq_table[0];
>  	}
> @@ -1373,14 +1383,15 @@ static ssize_t available_frequencies_show(struct device *d,
>  					  char *buf)
>  {
>  	struct devfreq *df = to_devfreq(d);
> +	struct devfreq_stats *stats = df->profile->stats;
>  	ssize_t count = 0;
>  	int i;
>  
>  	mutex_lock(&df->lock);
>  
> -	for (i = 0; i < df->profile->max_state; i++)
> +	for (i = 0; i < stats->max_state; i++)
>  		count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
> -				"%lu ", df->profile->freq_table[i]);
> +				"%lu ", stats->freq_table[i]);
>  
>  	mutex_unlock(&df->lock);
>  	/* Truncate the trailing space */
> @@ -1398,9 +1409,10 @@ static ssize_t trans_stat_show(struct device *dev,
>  {
>  	struct devfreq *devfreq = to_devfreq(dev);
>  	struct devfreq_dev_profile *profile = devfreq->profile;
> +	struct devfreq_stats *stats = profile->stats;
> +	unsigned int max_state = stats->max_state;
>  	ssize_t len;
>  	int i, j;
> -	unsigned int max_state = profile->max_state;
>  
>  	if (!devfreq->stop_polling &&
>  			devfreq_update_status(devfreq, devfreq->previous_freq))
> @@ -1411,45 +1423,45 @@ static ssize_t trans_stat_show(struct device *dev,
>  	len = sprintf(buf, "     From  :   To\n");
>  	len += sprintf(buf + len, "           :");
>  
> -	spin_lock(&profile->stats_lock);
> +	spin_lock(&stats->stats_lock);
>  	for (i = 0; i < max_state; i++)
>  		len += sprintf(buf + len, "%10lu",
> -				profile->freq_table[i]);
> +				stats->freq_table[i]);
>  
>  	len += sprintf(buf + len, "   time(ms)\n");
>  
>  	for (i = 0; i < max_state; i++) {
> -		if (profile->freq_table[i] == devfreq->previous_freq)
> +		if (stats->freq_table[i] == devfreq->previous_freq)
>  			len += sprintf(buf + len, "*");
>  		else
>  			len += sprintf(buf + len, " ");
>  
>  		len += sprintf(buf + len, "%10lu:",
> -				profile->freq_table[i]);
> +				stats->freq_table[i]);
>  		for (j = 0; j < max_state; j++)
>  			len += sprintf(buf + len, "%10u",
> -				profile->trans_table[(i * max_state) + j]);
> +				stats->trans_table[(i * max_state) + j]);
>  		len += sprintf(buf + len, "%10llu\n", (u64)
> -			jiffies64_to_msecs(profile->time_in_state[i]));
> +			jiffies64_to_msecs(stats->time_in_state[i]));
>  	}
>  
>  	len += sprintf(buf + len, "Total transition : %u\n",
> -					profile->total_trans);
> -	spin_unlock(&profile->stats_lock);
> +					stats->total_trans);
> +	spin_unlock(&stats->stats_lock);
>  	return len;
>  }
>  static DEVICE_ATTR_RO(trans_stat);
>  
> -static void defvreq_stats_clear_table(struct devfreq_dev_profile *profile)
> +static void defvreq_stats_clear_table(struct devfreq_stats *stats)
>  {
> -	unsigned int count = profile->max_state;
> -
> -	spin_lock(&profile->stats_lock);
> -	memset(profile->time_in_state, 0, count * sizeof(u64));
> -	memset(profile->trans_table, 0, count * count * sizeof(int));
> -	profile->last_time = get_jiffies_64();
> -	profile->total_trans = 0;
> -	spin_unlock(&profile->stats_lock);
> +	unsigned int count = stats->max_state;
> +
> +	spin_lock(&stats->stats_lock);
> +	memset(stats->time_in_state, 0, count * sizeof(u64));
> +	memset(stats->trans_table, 0, count * count * sizeof(int));
> +	stats->last_time = get_jiffies_64();
> +	stats->total_trans = 0;
> +	spin_unlock(&stats->stats_lock);
>  }
>  
>  static ssize_t trans_reset_store(struct device *dev,
> @@ -1459,7 +1471,7 @@ static ssize_t trans_reset_store(struct device *dev,
>  {
>  	struct devfreq *devfreq = to_devfreq(dev);
>  
> -	defvreq_stats_clear_table(devfreq->profile);
> +	defvreq_stats_clear_table(devfreq->profile->stats);
>  
>  	return count;
>  }
> diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
> index d9f377912c10..b212aae2bb3e 100644
> --- a/drivers/devfreq/exynos-bus.c
> +++ b/drivers/devfreq/exynos-bus.c
> @@ -496,9 +496,9 @@ static int exynos_bus_probe(struct platform_device *pdev)
>  	}
>  
>  out:
> -	max_state = bus->devfreq->profile->max_state;
> -	min_freq = (bus->devfreq->profile->freq_table[0] / 1000);
> -	max_freq = (bus->devfreq->profile->freq_table[max_state - 1] / 1000);
> +	max_state = profile->stats->max_state;
> +	min_freq = (profile->stats->freq_table[0] / 1000);
> +	max_freq = (profile->stats->freq_table[max_state - 1] / 1000);
>  	pr_info("exynos-bus: new bus device registered: %s (%6ld KHz ~ %6ld KHz)\n",
>  			dev_name(dev), min_freq, max_freq);
>  
> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> index 58308948b863..b2d87a88335c 100644
> --- a/drivers/devfreq/governor_passive.c
> +++ b/drivers/devfreq/governor_passive.c
> @@ -18,6 +18,8 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>  	struct devfreq_passive_data *p_data
>  			= (struct devfreq_passive_data *)devfreq->data;
>  	struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent;
> +	struct devfreq_stats *parent_stats = parent_devfreq->profile->stats;
> +	struct devfreq_stats *stats;
>  	unsigned long child_freq = ULONG_MAX;
>  	struct dev_pm_opp *opp;
>  	int i, count, ret = 0;
> @@ -47,10 +49,14 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>  	 * device. And then the index is used for getting the suitable
>  	 * new frequency for passive devfreq device.
>  	 */
> -	if (!devfreq->profile || !devfreq->profile->freq_table
> -		|| devfreq->profile->max_state <= 0)
> +	if (!devfreq->profile || !devfreq->profile->stats ||
> +	    devfreq->profile->stats->max_state <= 0 ||
> +	    !parent_devfreq->profile ||	!parent_devfreq->profile->stats ||
> +	    parent_devfreq->profile->stats->max_state <= 0)
>  		return -EINVAL;
>  
> +	stats = devfreq->profile->stats;
> +	parent_stats = parent_devfreq->profile->stats;
>  	/*
>  	 * The passive governor have to get the correct frequency from OPP
>  	 * list of parent device. Because in this case, *freq is temporary
> @@ -68,21 +74,21 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
>  	 * Get the OPP table's index of decided freqeuncy by governor
>  	 * of parent device.
>  	 */
> -	for (i = 0; i < parent_devfreq->profile->max_state; i++)
> -		if (parent_devfreq->profile->freq_table[i] == *freq)
> +	for (i = 0; i < parent_stats->max_state; i++)
> +		if (parent_stats->freq_table[i] == *freq)
>  			break;
>  
> -	if (i == parent_devfreq->profile->max_state) {
> +	if (i == parent_stats->max_state) {
>  		ret = -EINVAL;
>  		goto out;
>  	}
>  
>  	/* Get the suitable frequency by using index of parent device. */
> -	if (i < devfreq->profile->max_state) {
> -		child_freq = devfreq->profile->freq_table[i];
> +	if (i < stats->max_state) {
> +		child_freq = stats->freq_table[i];
>  	} else {
> -		count = devfreq->profile->max_state;
> -		child_freq = devfreq->profile->freq_table[count - 1];
> +		count = stats->max_state;
> +		child_freq = stats->freq_table[count - 1];
>  	}
>  
>  	/* Return the suitable frequency for passive device. */
> @@ -109,7 +115,7 @@ static int update_devfreq_passive(struct devfreq *devfreq, unsigned long freq)
>  	if (ret < 0)
>  		goto out;
>  
> -	if (devfreq->profile->freq_table
> +	if (devfreq->profile->stats
>  		&& (devfreq_update_status(devfreq, freq)))
>  		dev_err(&devfreq->dev,
>  			"Couldn't update frequency transition information.\n");
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 4ceb2a517a9c..8459af1a1583 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -64,6 +64,30 @@ struct devfreq_dev_status {
>   */
>  #define DEVFREQ_FLAG_LEAST_UPPER_BOUND		0x1
>  
> +/**
> + * struct devfreq_stats - Devfreq's transitions stats counters
> + * @freq_table:		Optional list of frequencies to support statistics
> + *			and freq_table must be generated in ascending order.
> + * @max_state:		The size of freq_table.
> + * @total_trans:	Number of devfreq transitions
> + * @trans_table:	Statistics of devfreq transitions
> + * @time_in_state:	Statistics of devfreq states
> + * @last_time:		The last time stats were updated
> + * @stats_lock:		Lock protecting trans_table, time_in_state,
> + *			last_time and total_trans used for statistics
> + */
> +struct devfreq_stats {
> +	unsigned long *freq_table;
> +	unsigned int max_state;
> +
> +	/* information for device frequency transition */
> +	unsigned int total_trans;
> +	unsigned int *trans_table;
> +	u64 *time_in_state;
> +	unsigned long long last_time;
> +	spinlock_t stats_lock;
> +};
> +
>  /**
>   * struct devfreq_dev_profile - Devfreq's user device profile
>   * @initial_freq:	The operating frequency when devfreq_add_device() is
> @@ -88,15 +112,7 @@ struct devfreq_dev_status {
>   *			from devfreq_remove_device() call. If the user
>   *			has registered devfreq->nb at a notifier-head,
>   *			this is the time to unregister it.
> - * @freq_table:		Optional list of frequencies to support statistics
> - *			and freq_table must be generated in ascending order.
> - * @max_state:		The size of freq_table.
> - * @total_trans:	Number of devfreq transitions
> - * @trans_table:	Statistics of devfreq transitions
> - * @time_in_state:	Statistics of devfreq states
> - * @last_time:		The last time stats were updated
> - * @stats_lock:		Lock protecting trans_table, time_in_state,
> - *			last_time and total_trans used for statistics
> + * @stats:		Statistics of devfreq states and state transitions
>   */
>  struct devfreq_dev_profile {
>  	unsigned long initial_freq;
> @@ -108,14 +124,7 @@ struct devfreq_dev_profile {
>  	int (*get_cur_freq)(struct device *dev, unsigned long *freq);
>  	void (*exit)(struct device *dev);
>  
> -	unsigned long *freq_table;
> -	unsigned int max_state;
> -	/* information for device frequency transition */
> -	unsigned int total_trans;
> -	unsigned int *trans_table;
> -	u64 *time_in_state;
> -	unsigned long long last_time;
> -	spinlock_t stats_lock;
> +	struct devfreq_stats *stats;
>  };
>  
>  /**
> 

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