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SubjectRe: [PATCH 7/7] devfreq: move statistics to separate struct
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Hi Chanwoo,

On 11/14/19 2:52 AM, Chanwoo Choi wrote:
> 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.

This argument is not a a technical one and the official upstream
kernel policy is to not depend on out-of-tree drivers.

Besides the ARM Mali drivers are full of code like:

#if LINUX_VERSION_CODE >= KERNEL_VERSION(x, y, z)
...
#else
...
#endif

so few more instances of similar code won't do any harm.. ;-)

> [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

I took a look at ARM Mali drivers source code anyway and I fail to
see a rationale behind their behavior of doing 'freq_table' and
'max_state' initialization in the driver itself (instead of leaving
it up to the devfreq core code, like all in-kernel drivers are doing
already).

Could you please explain rationale behind ARM Mali drivers' special
needs?

[ Both ARM Mali and devfreq core code are using generic PM OPP code
these days to do 'freq_table' and 'max_state' initialization, the
only difference seems to be that ARM Mali creates the frequency
table in the descending order (but there also seems to be no real
need for it). ]

Maybe this is an opportunity to simplify also the ARM Mali driver?

> 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.

Well, 'struct devfreq_stats *stats' can be trivially moved out of
'struct devfreq_profile' to 'struct devfreq' if you prefer it that
way..

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

> 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@samsung.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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