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Subject: Re: [RFC][PATCH 4/5] thermal: Add support for setting polling
 interval
To:     Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        rui.zhang@intel.com, amit.kucheria@verdurent.com
Cc:     linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
References: <20200504181616.175477-1-srinivas.pandruvada@linux.intel.com>
 <20200504181616.175477-5-srinivas.pandruvada@linux.intel.com>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <c2aad548-32c2-f008-5ce4-97b76a19271d@linaro.org>
Date:   Mon, 18 May 2020 18:51:00 +0200
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On 04/05/2020 20:16, Srinivas Pandruvada wrote:
> Add new attribute in the thermal syfs for setting temperature sampling
> interval when CONFIG_THERMAL_USER_EVENT_INTERFACE is defined. The default
> value is 0, which means no polling.
> 
> At this interval user space will get an event THERMAL_TEMP_SAMPLE with
> temperature sample. This reuses existing polling mecahnism when polling
> or passive delay is specified during zone registry. To avoid interference
> with passive and polling delay, this new polling attribute can't be used
> for those zones.

The userspace can get the temperature whenever it wants via the
temperature file. The polling is designed for a specific hardware and
the slope of the temperature graphic.

The userspace has the alternative of reading the temperature based on
its own timer or wait for (and stick to) the thermal framework sampling
rate. Adding a notification in the update is enough IMO.


> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> ---
>  drivers/thermal/thermal_core.c  |  7 +++++++
>  drivers/thermal/thermal_sysfs.c | 36 +++++++++++++++++++++++++++++++--
>  include/linux/thermal.h         |  1 +
>  3 files changed, 42 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 14770d882d42..17cd799b0073 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -313,6 +313,8 @@ static void monitor_thermal_zone(struct thermal_zone_device *tz)
>  		thermal_zone_device_set_polling(tz, tz->passive_delay);
>  	else if (tz->polling_delay)
>  		thermal_zone_device_set_polling(tz, tz->polling_delay);
> +	else if (tz->temp_polling_delay)
> +		thermal_zone_device_set_polling(tz, tz->temp_polling_delay);
>  	else
>  		thermal_zone_device_set_polling(tz, 0);
>  
> @@ -446,6 +448,11 @@ static void update_temperature(struct thermal_zone_device *tz)
>  	tz->temperature = temp;
>  	mutex_unlock(&tz->lock);
>  
> +	if (tz->temp_polling_delay) {
> +		thermal_dev_send_event(tz->id, THERMAL_TEMP_SAMPLE, temp);
> +		monitor_thermal_zone(tz);
> +	}
> +
>  	trace_thermal_temperature(tz);
>  	if (tz->last_temperature == THERMAL_TEMP_INVALID)
>  		dev_dbg(&tz->device, "last_temperature N/A, current_temperature=%d\n",
> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> index aa85424c3ac4..0df7997993fe 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -248,6 +248,36 @@ create_thres_attr(temp_thres_low);
>  create_thres_attr(temp_thres_high);
>  create_thres_attr(temp_thres_hyst);
>  
> +static ssize_t
> +temp_polling_delay_store(struct device *dev, struct device_attribute *attr,
> +		   const char *buf, size_t count)
> +{
> +	struct thermal_zone_device *tz = to_thermal_zone(dev);
> +	int val;
> +
> +	if (kstrtoint(buf, 10, &val))
> +		return -EINVAL;
> +
> +	if (val && val < 1000)
> +		return -EINVAL;
> +
> +	tz->temp_polling_delay = val;
> +	thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
> +
> +	return count;
> +}
> +
> +static ssize_t
> +temp_polling_delay_show(struct device *dev, struct device_attribute *attr,
> +		     char *buf)
> +{
> +	struct thermal_zone_device *tz = to_thermal_zone(dev);
> +
> +	return sprintf(buf, "%d\n", tz->temp_polling_delay);
> +}
> +
> +static DEVICE_ATTR_RW(temp_polling_delay);
> +
>  static int create_user_events_attrs(struct thermal_zone_device *tz)
>  {
>  	struct attribute **attrs;
> @@ -260,8 +290,8 @@ static int create_user_events_attrs(struct thermal_zone_device *tz)
>  	if (tz->ops->get_temp_thres_high)
>  		++index;
>  
> -	/* One additional space for NULL */
> -	attrs = kcalloc(index + 1, sizeof(*attrs), GFP_KERNEL);
> +	/* One additional space for NULL and temp_pollling_delay */
> +	attrs = kcalloc(index + 2, sizeof(*attrs), GFP_KERNEL);
>  	if (!attrs)
>  		return -ENOMEM;
>  
> @@ -312,6 +342,8 @@ static int create_user_events_attrs(struct thermal_zone_device *tz)
>  		attrs[index] = &tz->threshold_attrs[index].attr.attr;
>  		++index;
>  	}
> +	if (!tz->polling_delay && !tz->passive_delay)
> +		attrs[index++] = &dev_attr_temp_polling_delay.attr;
>  	attrs[index] = NULL;
>  	tz->threshold_attribute_group.attrs = attrs;
>  
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index ee9d79ace7ce..0ec4bd8c9c5c 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -216,6 +216,7 @@ struct thermal_zone_device {
>  	enum thermal_notify_event notify_event;
>  	struct attribute_group threshold_attribute_group;
>  	struct thermal_attr *threshold_attrs;
> +	int temp_polling_delay;
>  };
>  
>  /**
> 


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