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Message-ID: <20120207192903.GA8589@besouro>
Date: Tue, 7 Feb 2012 21:29:03 +0200
From: Eduardo Valentin <eduardo.valentin@...com>
To: Amit Kachhap <amit.kachhap@...aro.org>
Cc: eduardo.valentin@...com, linux-pm@...ts.linux-foundation.org,
linaro-dev@...ts.linaro.org, patches@...aro.org,
linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
rob.lee@...aro.org
Subject: Re: [linux-pm] [RFC PATCH] thermal: Add support to report cooling
statistics achieved by cooling devices
Hello Amit,
On Tue, Feb 07, 2012 at 09:52:40AM -0800, Amit Kachhap wrote:
> Hi eduardo,
>
> Thanks for the detail review.
>
> On 6 February 2012 23:09, Eduardo Valentin <eduardo.valentin@...com> wrote:
> > Hello Amit,
> >
> > some comments embedded.
> >
> > On Wed, Jan 18, 2012 at 02:51:07PM +0530, Amit Daniel Kachhap wrote:
> >> Add a sysfs node code to report effective cooling of all cooling devices
> >> attached to each trip points of a thermal zone. The cooling data reported
> >> will be absolute if the higher temperature trip points are arranged first
> >> otherwise the cooling stats is the cumulative effect of the earlier
> >> invoked cooling handlers.
> >>
> >> The basic assumption is that cooling devices will bring down the temperature
> >> in a symmetric manner and those statistics can be stored back and used for
> >> further tuning of the system.
> >>
> >> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@...aro.org>
> >> ---
> >> Documentation/thermal/sysfs-api.txt | 10 ++++
> >> drivers/thermal/thermal_sys.c | 96 +++++++++++++++++++++++++++++++++++
> >> include/linux/thermal.h | 8 +++
> >> 3 files changed, 114 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt
> >> index b61e46f..1db9a9d 100644
> >> --- a/Documentation/thermal/sysfs-api.txt
> >> +++ b/Documentation/thermal/sysfs-api.txt
> >> @@ -209,6 +209,13 @@ passive
> >> Valid values: 0 (disabled) or greater than 1000
> >> RW, Optional
> >>
> >> +trip_stats
> >> + This attribute presents the effective cooling generated from all the
> >> + cooling devices attached to a trip point. The output is a pair of value
> >> + for each trip point. Each pair represents
> >> + (trip index, cooling temperature difference in millidegree Celsius)
> >> + RO, Optional
> >> +
> >> *****************************
> >> * Cooling device attributes *
> >> *****************************
> >> @@ -261,6 +268,9 @@ method, the sys I/F structure will be built like this:
> >> |---cdev0_trip_point: 1 /* cdev0 can be used for passive */
> >> |---cdev1: --->/sys/class/thermal/cooling_device3
> >> |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
> >> + |---trip_stats 0 0
> >> + 1 8000 /*trip 1 causes 8 degree Celsius drop*/
> >> + 2 3000 /*trip 2 causes 3 degree Celsius drop*/
> >>
> >> |cooling_device0:
> >> |---type: Processor
> >> diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> >> index dd9a574..47e7b6e 100644
> >> --- a/drivers/thermal/thermal_sys.c
> >> +++ b/drivers/thermal/thermal_sys.c
> >> @@ -92,6 +92,64 @@ static void release_idr(struct idr *idr, struct mutex *lock, int id)
> >> if (lock)
> >> mutex_unlock(lock);
> >> }
> >> +static void update_cooling_stats(struct thermal_zone_device *tz, long cur_temp)
> >> +{
> >> + int count, max_index, cur_interval;
> >> + long trip_temp, max_temp = 0, cool_temp;
> >> + static int last_trip_level = -1;
> >
> > I got confused here. Are you sure using a static variable here is safe? I suppose this function
> > is called for any thermal_zone_device, which in turns, may have different amount of trips, and
> > different update rate. You may be using last_trip_level as reference for a different tz. Meaning,
> > you would be screwing the stat buffers silently.
> >
> > If that is the case, I suggest you to move this to your stat structure.
>
> Agree. This looks a clear problem. Surely i will move last_trip_level
> inside structure tz.
>
> >
> >> +
> >> + if (cur_temp >= tz->last_temperature)
> >> + return;
> >> +
> >> + /* find the trip according to last temperature */
> >> + for (count = 0; count < tz->trips; count++) {
> >> + tz->ops->get_trip_temp(tz, count, &trip_temp);
> >> + if (tz->last_temperature >= trip_temp) {
> >> + if (max_temp < trip_temp) {
> >> + max_temp = trip_temp;
> >> + max_index = count;
> >> + }
> >> + }
> >> + }
> >> +
> >> + if (!max_temp) {
> >> + last_trip_level = -1;
> >> + return;
> >> + }
> >> +
> >> + cur_interval = tz->stat[max_index].interval_ptr;
> >> + cool_temp = tz->last_temperature - cur_temp;
> >> +
> >> + if (last_trip_level != max_index) {
> >> + if (++cur_interval == INTERVAL_HISTORY)
> >> + cur_interval = 0;
> >> + tz->stat[max_index].cool_temp[cur_interval] = cool_temp;
> >> + tz->stat[max_index].interval_ptr = cur_interval;
> >> + last_trip_level = max_index;
> >> + } else {
> >> + tz->stat[max_index].cool_temp[cur_interval] += cool_temp;
> >
> > Why do you need to sum up here? Wouldn't this break your statistics? (I may completely missed your idea for last_trip_level).
> This will be summed up because after applying cooling action there is
> some cooling happening but not enough to change the trip level. So
> unless there is cooling enough to change the trip level I keep summing
> the temperature.
OK. You may want to add this explanation as a comment in the code.
> >
> >> + }
> >> +}
> >> +
> >> +static int calculate_cooling_temp_avg(struct thermal_zone_device *tz, int trip,
> >> + int *avg_cool)
> >> +{
> >> + int result = 0, count = 0, used_data = 0;
> >> +
> >> + if (trip > THERMAL_MAX_TRIPS)
> >
> > Shouldn't this be checked against tz->trips ? At least you allocate your *stat based on it.
> Correct.
> >
> >> + return -EINVAL;
> >> +
> >> + *avg_cool = 0;
> >> + for (count = 0; count < INTERVAL_HISTORY; count++) {
> >> + if (tz->stat[trip].cool_temp[count] > 0) {
> >> + *avg_cool += tz->stat[trip].cool_temp[count];
> >> + used_data++;
> >> + }
> >> + }
> >> + if (used_data > 1)
> >> + *avg_cool = (*avg_cool)/used_data;
> >
> > IIRC, the preferred operator style is (*avg_cool) / used_data
> OK.
> >
> >> + return result;
> >
> > result is used only to hold a 0 here?
> Ok This variable is not needed.
> >
> >> +}
> >>
> >> /* sys I/F for thermal zone */
> >>
> >> @@ -493,6 +551,26 @@ temp_crit_show(struct device *dev, struct device_attribute *attr,
> >> return sprintf(buf, "%ld\n", temperature);
> >> }
> >>
> >> +static ssize_t
> >> +thermal_cooling_trip_stats_show(struct device *dev,
> >> + struct device_attribute *attr,
> >> + char *buf)
> >> +{
> >> + struct thermal_zone_device *tz = to_thermal_zone(dev);
> >> + int avg_cool = 0, result, trip_index;
> >> + ssize_t len = 0;
> >> +
> >> + for (trip_index = 0; trip_index < tz->trips; trip_index++) {
> >> + result = calculate_cooling_temp_avg(tz,
> >> + trip_index, &avg_cool);
> >> + if (!result)
> >> + len += sprintf(buf + len, "%d %d\n",
> >> + trip_index, avg_cool);
> >> + }
> >> + return len;
> >> +}
> >> +static DEVICE_ATTR(trip_stats, 0444,
> >> + thermal_cooling_trip_stats_show, NULL);
> >>
> >> static struct thermal_hwmon_device *
> >> thermal_hwmon_lookup_by_type(const struct thermal_zone_device *tz)
> >> @@ -1049,6 +1127,8 @@ void thermal_zone_device_update(struct thermal_zone_device *tz)
> >> goto leave;
> >> }
> >>
> >> + update_cooling_stats(tz, temp);
> >> +
> >> for (count = 0; count < tz->trips; count++) {
> >> tz->ops->get_trip_type(tz, count, &trip_type);
> >> tz->ops->get_trip_temp(tz, count, &trip_temp);
> >> @@ -1181,6 +1261,13 @@ struct thermal_zone_device *thermal_zone_device_register(char *type,
> >> return ERR_PTR(result);
> >> }
> >>
> >> + /*Allocate variables for cooling stats*/
> >> + tz->stat = devm_kzalloc(&tz->device,
> >> + sizeof(struct thermal_cooling_stats) * trips,
> >> + GFP_KERNEL);
> >
> > You never free this memory here.
> yes because memory allocated with devm_kzalloc is freed automatically
> when the device is freed.
OK. missed the devm_ on your code. My bad.
> >
> >> + if (!tz->stat)
> >> + goto unregister;
> >> +
> >> /* sys I/F */
> >> if (type) {
> >> result = device_create_file(&tz->device, &dev_attr_type);
> >> @@ -1207,6 +1294,12 @@ struct thermal_zone_device *thermal_zone_device_register(char *type,
> >> passive = 1;
> >> }
> >>
> >> + if (trips > 0) {
> >> + result = device_create_file(&tz->device, &dev_attr_trip_stats);
> >> + if (result)
> >> + goto unregister;
> >
> > The failing paths after your allocation point must consider freeing the memory you requested.
> >
> >> + }
> >> +
> >> if (!passive)
> >> result = device_create_file(&tz->device,
> >> &dev_attr_passive);
> >> @@ -1282,6 +1375,9 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
> >> for (count = 0; count < tz->trips; count++)
> >> TRIP_POINT_ATTR_REMOVE(&tz->device, count);
> >>
> >> + if (tz->trips > 0)
> >> + device_remove_file(&tz->device, &dev_attr_trip_stats);
> >> +
> >
> > Amit,
> >
> > I think here it would be a good place to free the memory you allocated for *stat
> >
> >> thermal_remove_hwmon_sysfs(tz);
> >> release_idr(&thermal_tz_idr, &thermal_idr_lock, tz->id);
> >> idr_destroy(&tz->idr);
> >> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> >> index 47b4a27..47504c7 100644
> >> --- a/include/linux/thermal.h
> >> +++ b/include/linux/thermal.h
> >> @@ -72,6 +72,13 @@ struct thermal_cooling_device_ops {
> >> #define THERMAL_TRIPS_NONE -1
> >> #define THERMAL_MAX_TRIPS 12
> >> #define THERMAL_NAME_LENGTH 20
> >> +#define INTERVAL_HISTORY 12
> >> +
> >> +struct thermal_cooling_stats {
> >> + int cool_temp[INTERVAL_HISTORY];
> >> + int interval_ptr;
> >> +};
> >> +
> >> struct thermal_cooling_device {
> >> int id;
> >> char type[THERMAL_NAME_LENGTH];
> >> @@ -102,6 +109,7 @@ struct thermal_zone_device {
> >> struct list_head cooling_devices;
> >> struct idr idr;
> >> struct mutex lock; /* protect cooling devices list */
> >> + struct thermal_cooling_stats *stat;
> >> struct list_head node;
> >> struct delayed_work poll_queue;
> >> };
> >> --
> >> 1.7.1
> >>
> >> _______________________________________________
> >> linux-pm mailing list
> >> linux-pm@...ts.linux-foundation.org
> >> https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
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