Re: [PATCH 2/4] RFC Thermal: Introduce fair-share thermal governor

[Eduardo Valentin <eduardo.valentin@ti.com>]

Hello Durgadoss,

On Mon, Jun 11, 2012 at 11:09:32PM +0530, Durgadoss R wrote:
> This patch introduces a simple 'weight' based
> governor named fair-share governor. Whenever the
> thermal framework gets notified of the trip point
> violation, this governor (if configured), throttles
> the cooling devices associated with a thermal zone.
> 
> This mapping between a thermal zone and a cooling device
> and the effectiveness of cooling are provided in the
> platform layer.
> 
> Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
> ---
>  drivers/thermal/Kconfig      |    6 ++
>  drivers/thermal/Makefile     |    3 +-
>  drivers/thermal/fair_share.c |  111 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 119 insertions(+), 1 deletions(-)
>  create mode 100644 drivers/thermal/fair_share.c
> 
> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index 514a691..f5132f3 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -26,3 +26,9 @@ config SPEAR_THERMAL
>  	help
>  	  Enable this to plug the SPEAr thermal sensor driver into the Linux
>  	  thermal framework
> +
> +config FAIR_SHARE
> +	bool "Fair-share thermal governor"
> +	depends on THERMAL
> +	help
> +	  Enable this to manage platform thermals using fair-share governor.

A simple description of the policy would improve the helper...

> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> index a9fff0b..4ffe1a8 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -3,4 +3,5 @@
>  #
>  
>  obj-$(CONFIG_THERMAL)		+= thermal_sys.o
> -obj-$(CONFIG_SPEAR_THERMAL)		+= spear_thermal.o
> \ No newline at end of file
> +obj-$(CONFIG_SPEAR_THERMAL)		+= spear_thermal.o
> +obj-$(CONFIG_FAIR_SHARE)		+= fair_share.o
> diff --git a/drivers/thermal/fair_share.c b/drivers/thermal/fair_share.c
> new file mode 100644
> index 0000000..59af81d
> --- /dev/null
> +++ b/drivers/thermal/fair_share.c
> @@ -0,0 +1,111 @@
> +/*
> + *  fair_share.c - A simple weight based Thermal governor
> + *
> + *  Copyright (C) 2012 Intel Corp
> + *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
> + *
> + *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; version 2 of the License.
> + *
> + *  This program is distributed in the hope that it will be useful, but
> + *  WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + *  General Public License for more details.
> + *
> + *  You should have received a copy of the GNU General Public License along
> + *  with this program; if not, write to the Free Software Foundation, Inc.,
> + *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
> + *
> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/module.h>
> +#include <linux/thermal.h>
> +
> +/**
> + * get_trip_level: - obtains the current trip level for a zone
> + * @tz:		thermal zone device
> + */
> +int get_trip_level(struct thermal_zone_device *tz)
> +{
> +	int count = 0;
> +	unsigned long cur_temp, trip_temp;
> +
> +	if (tz->trips == 0 || !tz->ops->get_trip_temp)
> +		return 0;
> +
> +	tz->ops->get_temp(tz, &cur_temp);
> +
> +	for (count = 0; count < tz->trips; count++) {
> +		tz->ops->get_trip_temp(tz, count, &trip_temp);
> +		if (cur_temp < trip_temp)
> +			break;
> +	}
> +	return count;
> +}
> +
> +/**
> + * fair_share_throttle - throttles devices asscciated with the given zone
> + * @tz - thermal_zone_device
> + *
> + * Throttling Logic: This uses three parameters to calculate the new
> + * throttle state of the cooling devices associated with the given zone.
> + *
> + * P1. max_state: Maximum throttle state exposed by the cooling device.
> + * P2. weight[i]/100:
> + *	How 'effective' the 'i'th device is, in cooling the given zone.
> + * P3. cur_trip_level/max_no_of_trips:
> + *	This describes the extent to which the devices should be throttled.
> + *	We do not want to throttle too much when we trip a lower temperature,
> + *	whereas the throttling is at full swing if we trip critical levels.
> + *	(Heavily assumes the trip points are in ascending order)
> + * new_state of cooling device = P3 * P2 * P1
> + */
> +int fair_share_throttle(struct thermal_zone_device *tz)
> +{
> +	struct thermal_zone_params *tzp;
> +	struct thermal_cooling_device *cdev;
> +	unsigned long max_state, new_state;
> +	int i;
> +
> +	int cur_trip_level = get_trip_level(tz);
> +
> +	/* Do not throttle:
> +	 * if there are no parameters defined for this zone
> +	 * if current trip level is 0 (for performance reasons)
> +	 */

Nip: I suppose the kernel coding for comments should be:
+	/*
+	 * Do not throttle:
+	 * if there are no parameters defined for this zone
+	 * if current trip level is 0 (for performance reasons)
+	 */


> +	if (!tz->tzp || cur_trip_level == 0)
> +		return 0;
> +
> +	tzp = tz->tzp;
> +
> +	for (i = 0; i < tzp->num_cdevs; i++) {
> +		/*
> +		 * Do not throttle:
> +		 * if this device cannot cool the zone, or
> +		 * if the cooling device does not exist anymore
> +		 */
> +		if (tzp->weights[i] == 0 || !tzp->cdevs[i])
> +			continue;
> +
> +		cdev = tzp->cdevs[i];
> +		cdev->ops->get_max_state(cdev, &max_state);
> +
> +		new_state =
> +		(long)(tzp->weights[i] * cur_trip_level * max_state) /
> +		(100 * tz->trips);

I think, while merging your work with Rui's, you need to take care of the
cooling state range bound to the trip point..

> +
> +		cdev->ops->set_cur_state(cdev, new_state);
> +	}

Nip: Add an extra line here.

> +	return 0;
> +}
> +EXPORT_SYMBOL(fair_share_throttle);
> +
> +MODULE_AUTHOR("Durgadoss R");
> +MODULE_DESCRIPTION("A simple weight based thermal throttling governor");
> +MODULE_LICENSE("GPL");
> -- 
> 1.7.0.4
>