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Date: Wed, 11 Jan 2012 23:54:25 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: MyungJoo Ham <myungjoo.ham@...sung.com>
Cc: linux-kernel@...r.kernel.org,
Linux PM list <linux-pm@...r.kernel.org>,
Kyungmin Park <kyungmin.park@...sung.com>,
Kevin Hilman <khilman@...com>,
Mike Turquette <mturquette@...com>, myungjoo.ham@...il.com
Subject: Re: [PATCH 1/2] PM / devfreq: add min/max_freq limit requested by users.
On Wednesday, January 11, 2012, MyungJoo Ham wrote:
> The frequency requested to devfreq device driver from devfreq governors
> is restricted by min_freq and max_freq input.
Can you please give us a bit more information about why this change is
necessary or desirable?
Rafael
> Signed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@...sung.com>
> ---
> drivers/devfreq/devfreq.c | 70 +++++++++++++++++++++++++++++
> drivers/devfreq/governor_performance.c | 5 ++-
> drivers/devfreq/governor_powersave.c | 2 +-
> drivers/devfreq/governor_simpleondemand.c | 12 ++++-
> drivers/devfreq/governor_userspace.c | 15 +++++-
> include/linux/devfreq.h | 5 ++
> 6 files changed, 101 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 59d24e9..358d129 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -502,12 +502,82 @@ static ssize_t show_central_polling(struct device *dev,
> !to_devfreq(dev)->governor->no_central_polling);
> }
>
> +static ssize_t store_min_freq(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct devfreq *df = to_devfreq(dev);
> + unsigned long value;
> + int ret;
> + unsigned long max;
> +
> + ret = sscanf(buf, "%lu", &value);
> + if (ret != 1)
> + goto out;
> +
> + mutex_lock(&df->lock);
> + max = df->max_freq;
> + if (value && max && value > max) {
> + ret = -EINVAL;
> + goto unlock;
> + }
> +
> + df->min_freq = value;
> + update_devfreq(df);
> + ret = count;
> +unlock:
> + mutex_unlock(&df->lock);
> +out:
> + return ret;
> +}
> +
> +static ssize_t show_min_freq(struct device *dev, struct device_attribute *attr,
> + char *buf)
> +{
> + return sprintf(buf, "%lu\n", to_devfreq(dev)->min_freq);
> +}
> +
> +static ssize_t store_max_freq(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct devfreq *df = to_devfreq(dev);
> + unsigned long value;
> + int ret;
> + unsigned long min;
> +
> + ret = sscanf(buf, "%lu", &value);
> + if (ret != 1)
> + goto out;
> +
> + mutex_lock(&df->lock);
> + min = df->min_freq;
> + if (value && min && value < min) {
> + ret = -EINVAL;
> + goto unlock;
> + }
> +
> + df->max_freq = value;
> + update_devfreq(df);
> + ret = count;
> +unlock:
> + mutex_unlock(&df->lock);
> +out:
> + return ret;
> +}
> +
> +static ssize_t show_max_freq(struct device *dev, struct device_attribute *attr,
> + char *buf)
> +{
> + return sprintf(buf, "%lu\n", to_devfreq(dev)->max_freq);
> +}
> +
> static struct device_attribute devfreq_attrs[] = {
> __ATTR(governor, S_IRUGO, show_governor, NULL),
> __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
> __ATTR(central_polling, S_IRUGO, show_central_polling, NULL),
> __ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
> store_polling_interval),
> + __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),
> + __ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq),
> { },
> };
>
> diff --git a/drivers/devfreq/governor_performance.c b/drivers/devfreq/governor_performance.c
> index c0596b2..574a06b 100644
> --- a/drivers/devfreq/governor_performance.c
> +++ b/drivers/devfreq/governor_performance.c
> @@ -18,7 +18,10 @@ static int devfreq_performance_func(struct devfreq *df,
> * target callback should be able to get floor value as
> * said in devfreq.h
> */
> - *freq = UINT_MAX;
> + if (!df->max_freq)
> + *freq = UINT_MAX;
> + else
> + *freq = df->max_freq;
> return 0;
> }
>
> diff --git a/drivers/devfreq/governor_powersave.c b/drivers/devfreq/governor_powersave.c
> index 2483a85..d742d4a 100644
> --- a/drivers/devfreq/governor_powersave.c
> +++ b/drivers/devfreq/governor_powersave.c
> @@ -18,7 +18,7 @@ static int devfreq_powersave_func(struct devfreq *df,
> * target callback should be able to get ceiling value as
> * said in devfreq.h
> */
> - *freq = 0;
> + *freq = df->min_freq;
> return 0;
> }
>
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index efad8dc..a2e3eae 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -25,6 +25,7 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
> unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
> struct devfreq_simple_ondemand_data *data = df->data;
> + unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX;
>
> if (err)
> return err;
> @@ -41,7 +42,7 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
>
> /* Assume MAX if it is going to be divided by zero */
> if (stat.total_time == 0) {
> - *freq = UINT_MAX;
> + *freq = max;
> return 0;
> }
>
> @@ -54,13 +55,13 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> /* Set MAX if it's busy enough */
> if (stat.busy_time * 100 >
> stat.total_time * dfso_upthreshold) {
> - *freq = UINT_MAX;
> + *freq = max;
> return 0;
> }
>
> /* Set MAX if we do not know the initial frequency */
> if (stat.current_frequency == 0) {
> - *freq = UINT_MAX;
> + *freq = max;
> return 0;
> }
>
> @@ -79,6 +80,11 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
> *freq = (unsigned long) b;
>
> + if (df->min_freq && *freq < df->min_freq)
> + *freq = df->min_freq;
> + if (df->max_freq && *freq > df->max_freq)
> + *freq = df->max_freq;
> +
> return 0;
> }
>
> diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
> index 4f8b563..0681246 100644
> --- a/drivers/devfreq/governor_userspace.c
> +++ b/drivers/devfreq/governor_userspace.c
> @@ -25,10 +25,19 @@ static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
> {
> struct userspace_data *data = df->data;
>
> - if (!data->valid)
> + if (data->valid) {
> + unsigned long adjusted_freq = data->user_frequency;
> +
> + if (df->max_freq && adjusted_freq > df->max_freq)
> + adjusted_freq = df->max_freq;
> +
> + if (df->min_freq && adjusted_freq < df->min_freq)
> + adjusted_freq = df->min_freq;
> +
> + *freq = adjusted_freq;
> + } else {
> *freq = df->previous_freq; /* No user freq specified yet */
> - else
> - *freq = data->user_frequency;
> + }
> return 0;
> }
>
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 98ce812..e9385bf 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -124,6 +124,8 @@ struct devfreq_governor {
> * touch this.
> * @being_removed a flag to mark that this object is being removed in
> * order to prevent trying to remove the object multiple times.
> + * @min_freq Limit minimum frequency requested by user (0: none)
> + * @max_freq Limit maximum frequency requested by user (0: none)
> *
> * This structure stores the devfreq information for a give device.
> *
> @@ -149,6 +151,9 @@ struct devfreq {
> void *data; /* private data for governors */
>
> bool being_removed;
> +
> + unsigned long min_freq;
> + unsigned long max_freq;
> };
>
> #if defined(CONFIG_PM_DEVFREQ)
>
--
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