drivers/sbus/char/bbc_envctrl.c - kernel/msm-4.9 - Gitiles

 /* $Id: bbc_envctrl.c,v 1.4 2001/04/06 16:48:08 davem Exp $
  * bbc_envctrl.c: UltraSPARC-III environment control driver.
  *
  * Copyright (C) 2001 David S. Miller (davem@redhat.com)
  */

 #include <linux/kthread.h>
 #include <linux/delay.h>
 #include <linux/kmod.h>
 #include <linux/reboot.h>
 #include <asm/oplib.h>
 #include <asm/ebus.h>

 #include "bbc_i2c.h"
 #include "max1617.h"

 #undef ENVCTRL_TRACE

 /* WARNING: Making changes to this driver is very dangerous.
  *          If you misprogram the sensor chips they can
  *          cut the power on you instantly.
  */

 /* Two temperature sensors exist in the SunBLADE-1000 enclosure.
  * Both are implemented using max1617 i2c devices.  Each max1617
  * monitors 2 temperatures, one for one of the cpu dies and the other
  * for the ambient temperature.
  *
  * The max1617 is capable of being programmed with power-off
  * temperature values, one low limit and one high limit.  These
  * can be controlled independently for the cpu or ambient temperature.
  * If a limit is violated, the power is simply shut off.  The frequency
  * with which the max1617 does temperature sampling can be controlled
  * as well.
  *
  * Three fans exist inside the machine, all three are controlled with
  * an i2c digital to analog converter.  There is a fan directed at the
  * two processor slots, another for the rest of the enclosure, and the
  * third is for the power supply.  The first two fans may be speed
  * controlled by changing the voltage fed to them.  The third fan may
  * only be completely off or on.  The third fan is meant to only be
  * disabled/enabled when entering/exiting the lowest power-saving
  * mode of the machine.
  *
  * An environmental control kernel thread periodically monitors all
  * temperature sensors.  Based upon the samples it will adjust the
  * fan speeds to try and keep the system within a certain temperature
  * range (the goal being to make the fans as quiet as possible without
  * allowing the system to get too hot).
  *
  * If the temperature begins to rise/fall outside of the acceptable
  * operating range, a periodic warning will be sent to the kernel log.
  * The fans will be put on full blast to attempt to deal with this
  * situation.  After exceeding the acceptable operating range by a
  * certain threshold, the kernel thread will shut down the system.
  * Here, the thread is attempting to shut the machine down cleanly
  * before the hardware based power-off event is triggered.
  */

 /* These settings are in Celsius.  We use these defaults only
  * if we cannot interrogate the cpu-fru SEEPROM.
  */
 struct temp_limits {
 	s8 high_pwroff, high_shutdown, high_warn;
 	s8 low_warn, low_shutdown, low_pwroff;
 };

 static struct temp_limits cpu_temp_limits[2] = {
 	{ 100, 85, 80, 5, -5, -10 },
 	{ 100, 85, 80, 5, -5, -10 },
 };

 static struct temp_limits amb_temp_limits[2] = {
 	{ 65, 55, 40, 5, -5, -10 },
 	{ 65, 55, 40, 5, -5, -10 },
 };

 enum fan_action { FAN_SLOWER, FAN_SAME, FAN_FASTER, FAN_FULLBLAST, FAN_STATE_MAX };

 struct bbc_cpu_temperature {
 	struct bbc_cpu_temperature	*next;

 	struct bbc_i2c_client		*client;
 	int				index;

 	/* Current readings, and history. */
 	s8				curr_cpu_temp;
 	s8				curr_amb_temp;
 	s8				prev_cpu_temp;
 	s8				prev_amb_temp;
 	s8				avg_cpu_temp;
 	s8				avg_amb_temp;

 	int				sample_tick;

 	enum fan_action			fan_todo[2];
 #define FAN_AMBIENT	0
 #define FAN_CPU		1
 };

 struct bbc_cpu_temperature *all_bbc_temps;

 struct bbc_fan_control {
 	struct bbc_fan_control 	*next;

 	struct bbc_i2c_client 	*client;
 	int 			index;

 	int			psupply_fan_on;
 	int			cpu_fan_speed;
 	int			system_fan_speed;
 };

 struct bbc_fan_control *all_bbc_fans;

 #define CPU_FAN_REG	0xf0
 #define SYS_FAN_REG	0xf2
 #define PSUPPLY_FAN_REG	0xf4

 #define FAN_SPEED_MIN	0x0c
 #define FAN_SPEED_MAX	0x3f

 #define PSUPPLY_FAN_ON	0x1f
 #define PSUPPLY_FAN_OFF	0x00

 static void set_fan_speeds(struct bbc_fan_control *fp)
 {
 	/* Put temperatures into range so we don't mis-program
 	 * the hardware.
 	 */
 	if (fp->cpu_fan_speed < FAN_SPEED_MIN)
 		fp->cpu_fan_speed = FAN_SPEED_MIN;
 	if (fp->cpu_fan_speed > FAN_SPEED_MAX)
 		fp->cpu_fan_speed = FAN_SPEED_MAX;
 	if (fp->system_fan_speed < FAN_SPEED_MIN)
 		fp->system_fan_speed = FAN_SPEED_MIN;
 	if (fp->system_fan_speed > FAN_SPEED_MAX)
 		fp->system_fan_speed = FAN_SPEED_MAX;
 #ifdef ENVCTRL_TRACE
 	printk("fan%d: Changed fan speed to cpu(%02x) sys(%02x)\n",
 	       fp->index,
 	       fp->cpu_fan_speed, fp->system_fan_speed);
 #endif

 	bbc_i2c_writeb(fp->client, fp->cpu_fan_speed, CPU_FAN_REG);
 	bbc_i2c_writeb(fp->client, fp->system_fan_speed, SYS_FAN_REG);
 	bbc_i2c_writeb(fp->client,
 		       (fp->psupply_fan_on ?
 			PSUPPLY_FAN_ON : PSUPPLY_FAN_OFF),
 		       PSUPPLY_FAN_REG);
 }

 static void get_current_temps(struct bbc_cpu_temperature *tp)
 {
 	tp->prev_amb_temp = tp->curr_amb_temp;
 	bbc_i2c_readb(tp->client,
 		      (unsigned char *) &tp->curr_amb_temp,
 		      MAX1617_AMB_TEMP);
 	tp->prev_cpu_temp = tp->curr_cpu_temp;
 	bbc_i2c_readb(tp->client,
 		      (unsigned char *) &tp->curr_cpu_temp,
 		      MAX1617_CPU_TEMP);
 #ifdef ENVCTRL_TRACE
 	printk("temp%d: cpu(%d C) amb(%d C)\n",
 	       tp->index,
 	       (int) tp->curr_cpu_temp, (int) tp->curr_amb_temp);
 #endif
 }


 static void do_envctrl_shutdown(struct bbc_cpu_temperature *tp)
 {
 	static int shutting_down = 0;
 	char *type = "???";
 	s8 val = -1;

 	if (shutting_down != 0)
 		return;

 	if (tp->curr_amb_temp >= amb_temp_limits[tp->index].high_shutdown ||
 	    tp->curr_amb_temp < amb_temp_limits[tp->index].low_shutdown) {
 		type = "ambient";
 		val = tp->curr_amb_temp;
 	} else if (tp->curr_cpu_temp >= cpu_temp_limits[tp->index].high_shutdown ||
 		   tp->curr_cpu_temp < cpu_temp_limits[tp->index].low_shutdown) {
 		type = "CPU";
 		val = tp->curr_cpu_temp;
 	}

 	printk(KERN_CRIT "temp%d: Outside of safe %s "
 	       "operating temperature, %d C.\n",
 	       tp->index, type, val);

 	printk(KERN_CRIT "kenvctrld: Shutting down the system now.\n");

 	shutting_down = 1;
 	if (orderly_poweroff(true) < 0)
 		printk(KERN_CRIT "envctrl: shutdown execution failed\n");
 }

 #define WARN_INTERVAL	(30 * HZ)

 static void analyze_ambient_temp(struct bbc_cpu_temperature *tp, unsigned long *last_warn, int tick)
 {
 	int ret = 0;

 	if (time_after(jiffies, (*last_warn + WARN_INTERVAL))) {
 		if (tp->curr_amb_temp >=
 		    amb_temp_limits[tp->index].high_warn) {
 			printk(KERN_WARNING "temp%d: "
 			       "Above safe ambient operating temperature, %d C.\n",
 			       tp->index, (int) tp->curr_amb_temp);
 			ret = 1;
 		} else if (tp->curr_amb_temp <
 			   amb_temp_limits[tp->index].low_warn) {
 			printk(KERN_WARNING "temp%d: "
 			       "Below safe ambient operating temperature, %d C.\n",
 			       tp->index, (int) tp->curr_amb_temp);
 			ret = 1;
 		}
 		if (ret)
 			*last_warn = jiffies;
 	} else if (tp->curr_amb_temp >= amb_temp_limits[tp->index].high_warn ||
 		   tp->curr_amb_temp < amb_temp_limits[tp->index].low_warn)
 		ret = 1;

 	/* Now check the shutdown limits. */
 	if (tp->curr_amb_temp >= amb_temp_limits[tp->index].high_shutdown ||
 	    tp->curr_amb_temp < amb_temp_limits[tp->index].low_shutdown) {
 		do_envctrl_shutdown(tp);
 		ret = 1;
 	}

 	if (ret) {
 		tp->fan_todo[FAN_AMBIENT] = FAN_FULLBLAST;
 	} else if ((tick & (8 - 1)) == 0) {
 		s8 amb_goal_hi = amb_temp_limits[tp->index].high_warn - 10;
 		s8 amb_goal_lo;

 		amb_goal_lo = amb_goal_hi - 3;

 		/* We do not try to avoid 'too cold' events.  Basically we
 		 * only try to deal with over-heating and fan noise reduction.
 		 */
 		if (tp->avg_amb_temp < amb_goal_hi) {
 			if (tp->avg_amb_temp >= amb_goal_lo)
 				tp->fan_todo[FAN_AMBIENT] = FAN_SAME;
 			else
 				tp->fan_todo[FAN_AMBIENT] = FAN_SLOWER;
 		} else {
 			tp->fan_todo[FAN_AMBIENT] = FAN_FASTER;
 		}
 	} else {
 		tp->fan_todo[FAN_AMBIENT] = FAN_SAME;
 	}
 }

 static void analyze_cpu_temp(struct bbc_cpu_temperature *tp, unsigned long *last_warn, int tick)
 {
 	int ret = 0;

 	if (time_after(jiffies, (*last_warn + WARN_INTERVAL))) {
 		if (tp->curr_cpu_temp >=
 		    cpu_temp_limits[tp->index].high_warn) {
 			printk(KERN_WARNING "temp%d: "
 			       "Above safe CPU operating temperature, %d C.\n",
 			       tp->index, (int) tp->curr_cpu_temp);
 			ret = 1;
 		} else if (tp->curr_cpu_temp <
 			   cpu_temp_limits[tp->index].low_warn) {
 			printk(KERN_WARNING "temp%d: "
 			       "Below safe CPU operating temperature, %d C.\n",
 			       tp->index, (int) tp->curr_cpu_temp);
 			ret = 1;
 		}
 		if (ret)
 			*last_warn = jiffies;
 	} else if (tp->curr_cpu_temp >= cpu_temp_limits[tp->index].high_warn ||
 		   tp->curr_cpu_temp < cpu_temp_limits[tp->index].low_warn)
 		ret = 1;

 	/* Now check the shutdown limits. */
 	if (tp->curr_cpu_temp >= cpu_temp_limits[tp->index].high_shutdown ||
 	    tp->curr_cpu_temp < cpu_temp_limits[tp->index].low_shutdown) {
 		do_envctrl_shutdown(tp);
 		ret = 1;
 	}

 	if (ret) {
 		tp->fan_todo[FAN_CPU] = FAN_FULLBLAST;
 	} else if ((tick & (8 - 1)) == 0) {
 		s8 cpu_goal_hi = cpu_temp_limits[tp->index].high_warn - 10;
 		s8 cpu_goal_lo;

 		cpu_goal_lo = cpu_goal_hi - 3;

 		/* We do not try to avoid 'too cold' events.  Basically we
 		 * only try to deal with over-heating and fan noise reduction.
 		 */
 		if (tp->avg_cpu_temp < cpu_goal_hi) {
 			if (tp->avg_cpu_temp >= cpu_goal_lo)
 				tp->fan_todo[FAN_CPU] = FAN_SAME;
 			else
 				tp->fan_todo[FAN_CPU] = FAN_SLOWER;
 		} else {
 			tp->fan_todo[FAN_CPU] = FAN_FASTER;
 		}
 	} else {
 		tp->fan_todo[FAN_CPU] = FAN_SAME;
 	}
 }

 static void analyze_temps(struct bbc_cpu_temperature *tp, unsigned long *last_warn)
 {
 	tp->avg_amb_temp = (s8)((int)((int)tp->avg_amb_temp + (int)tp->curr_amb_temp) / 2);
 	tp->avg_cpu_temp = (s8)((int)((int)tp->avg_cpu_temp + (int)tp->curr_cpu_temp) / 2);

 	analyze_ambient_temp(tp, last_warn, tp->sample_tick);
 	analyze_cpu_temp(tp, last_warn, tp->sample_tick);

 	tp->sample_tick++;
 }

 static enum fan_action prioritize_fan_action(int which_fan)
 {
 	struct bbc_cpu_temperature *tp;
 	enum fan_action decision = FAN_STATE_MAX;

 	/* Basically, prioritize what the temperature sensors
 	 * recommend we do, and perform that action on all the
 	 * fans.
 	 */
 	for (tp = all_bbc_temps; tp; tp = tp->next) {
 		if (tp->fan_todo[which_fan] == FAN_FULLBLAST) {
 			decision = FAN_FULLBLAST;
 			break;
 		}
 		if (tp->fan_todo[which_fan] == FAN_SAME &&
 		    decision != FAN_FASTER)
 			decision = FAN_SAME;
 		else if (tp->fan_todo[which_fan] == FAN_FASTER)
 			decision = FAN_FASTER;
 		else if (decision != FAN_FASTER &&
 			 decision != FAN_SAME &&
 			 tp->fan_todo[which_fan] == FAN_SLOWER)
 			decision = FAN_SLOWER;
 	}
 	if (decision == FAN_STATE_MAX)
 		decision = FAN_SAME;

 	return decision;
 }

 static int maybe_new_ambient_fan_speed(struct bbc_fan_control *fp)
 {
 	enum fan_action decision = prioritize_fan_action(FAN_AMBIENT);
 	int ret;

 	if (decision == FAN_SAME)
 		return 0;

 	ret = 1;
 	if (decision == FAN_FULLBLAST) {
 		if (fp->system_fan_speed >= FAN_SPEED_MAX)
 			ret = 0;
 		else
 			fp->system_fan_speed = FAN_SPEED_MAX;
 	} else {
 		if (decision == FAN_FASTER) {
 			if (fp->system_fan_speed >= FAN_SPEED_MAX)
 				ret = 0;
 			else
 				fp->system_fan_speed += 2;
 		} else {
 			int orig_speed = fp->system_fan_speed;

 			if (orig_speed <= FAN_SPEED_MIN ||
 			    orig_speed <= (fp->cpu_fan_speed - 3))
 				ret = 0;
 			else
 				fp->system_fan_speed -= 1;
 		}
 	}

 	return ret;
 }

 static int maybe_new_cpu_fan_speed(struct bbc_fan_control *fp)
 {
 	enum fan_action decision = prioritize_fan_action(FAN_CPU);
 	int ret;

 	if (decision == FAN_SAME)
 		return 0;

 	ret = 1;
 	if (decision == FAN_FULLBLAST) {
 		if (fp->cpu_fan_speed >= FAN_SPEED_MAX)
 			ret = 0;
 		else
 			fp->cpu_fan_speed = FAN_SPEED_MAX;
 	} else {
 		if (decision == FAN_FASTER) {
 			if (fp->cpu_fan_speed >= FAN_SPEED_MAX)
 				ret = 0;
 			else {
 				fp->cpu_fan_speed += 2;
 				if (fp->system_fan_speed <
 				    (fp->cpu_fan_speed - 3))
 					fp->system_fan_speed =
 						fp->cpu_fan_speed - 3;
 			}
 		} else {
 			if (fp->cpu_fan_speed <= FAN_SPEED_MIN)
 				ret = 0;
 			else
 				fp->cpu_fan_speed -= 1;
 		}
 	}

 	return ret;
 }

 static void maybe_new_fan_speeds(struct bbc_fan_control *fp)
 {
 	int new;

 	new  = maybe_new_ambient_fan_speed(fp);
 	new |= maybe_new_cpu_fan_speed(fp);

 	if (new)
 		set_fan_speeds(fp);
 }

 static void fans_full_blast(void)
 {
 	struct bbc_fan_control *fp;

 	/* Since we will not be monitoring things anymore, put
 	 * the fans on full blast.
 	 */
 	for (fp = all_bbc_fans; fp; fp = fp->next) {
 		fp->cpu_fan_speed = FAN_SPEED_MAX;
 		fp->system_fan_speed = FAN_SPEED_MAX;
 		fp->psupply_fan_on = 1;
 		set_fan_speeds(fp);
 	}
 }

 #define POLL_INTERVAL	(5 * 1000)
 static unsigned long last_warning_jiffies;
 static struct task_struct *kenvctrld_task;

 static int kenvctrld(void *__unused)
 {
 	printk(KERN_INFO "bbc_envctrl: kenvctrld starting...\n");
 	last_warning_jiffies = jiffies - WARN_INTERVAL;
 	for (;;) {
 		struct bbc_cpu_temperature *tp;
 		struct bbc_fan_control *fp;

 		msleep_interruptible(POLL_INTERVAL);
 		if (kthread_should_stop())
 			break;

 		for (tp = all_bbc_temps; tp; tp = tp->next) {
 			get_current_temps(tp);
 			analyze_temps(tp, &last_warning_jiffies);
 		}
 		for (fp = all_bbc_fans; fp; fp = fp->next)
 			maybe_new_fan_speeds(fp);
 	}
 	printk(KERN_INFO "bbc_envctrl: kenvctrld exiting...\n");

 	fans_full_blast();

 	return 0;
 }

 static void attach_one_temp(struct linux_ebus_child *echild, int temp_idx)
 {
 	struct bbc_cpu_temperature *tp;

 	tp = kzalloc(sizeof(*tp), GFP_KERNEL);
 	if (!tp)
 		return;

 	tp->client = bbc_i2c_attach(echild);
 	if (!tp->client) {
 		kfree(tp);
 		return;
 	}

 	tp->index = temp_idx;
 	{
 		struct bbc_cpu_temperature **tpp = &all_bbc_temps;
 		while (*tpp)
 			tpp = &((*tpp)->next);
 		tp->next = NULL;
 		*tpp = tp;
 	}

 	/* Tell it to convert once every 5 seconds, clear all cfg
 	 * bits.
 	 */
 	bbc_i2c_writeb(tp->client, 0x00, MAX1617_WR_CFG_BYTE);
 	bbc_i2c_writeb(tp->client, 0x02, MAX1617_WR_CVRATE_BYTE);

 	/* Program the hard temperature limits into the chip. */
 	bbc_i2c_writeb(tp->client, amb_temp_limits[tp->index].high_pwroff,
 		       MAX1617_WR_AMB_HIGHLIM);
 	bbc_i2c_writeb(tp->client, amb_temp_limits[tp->index].low_pwroff,
 		       MAX1617_WR_AMB_LOWLIM);
 	bbc_i2c_writeb(tp->client, cpu_temp_limits[tp->index].high_pwroff,
 		       MAX1617_WR_CPU_HIGHLIM);
 	bbc_i2c_writeb(tp->client, cpu_temp_limits[tp->index].low_pwroff,
 		       MAX1617_WR_CPU_LOWLIM);

 	get_current_temps(tp);
 	tp->prev_cpu_temp = tp->avg_cpu_temp = tp->curr_cpu_temp;
 	tp->prev_amb_temp = tp->avg_amb_temp = tp->curr_amb_temp;

 	tp->fan_todo[FAN_AMBIENT] = FAN_SAME;
 	tp->fan_todo[FAN_CPU] = FAN_SAME;
 }

 static void attach_one_fan(struct linux_ebus_child *echild, int fan_idx)
 {
 	struct bbc_fan_control *fp;

 	fp = kzalloc(sizeof(*fp), GFP_KERNEL);
 	if (!fp)
 		return;

 	fp->client = bbc_i2c_attach(echild);
 	if (!fp->client) {
 		kfree(fp);
 		return;
 	}

 	fp->index = fan_idx;

 	{
 		struct bbc_fan_control **fpp = &all_bbc_fans;
 		while (*fpp)
 			fpp = &((*fpp)->next);
 		fp->next = NULL;
 		*fpp = fp;
 	}

 	/* The i2c device controlling the fans is write-only.
 	 * So the only way to keep track of the current power
 	 * level fed to the fans is via software.  Choose half
 	 * power for cpu/system and 'on' fo the powersupply fan
 	 * and set it now.
 	 */
 	fp->psupply_fan_on = 1;
 	fp->cpu_fan_speed = (FAN_SPEED_MAX - FAN_SPEED_MIN) / 2;
 	fp->cpu_fan_speed += FAN_SPEED_MIN;
 	fp->system_fan_speed = (FAN_SPEED_MAX - FAN_SPEED_MIN) / 2;
 	fp->system_fan_speed += FAN_SPEED_MIN;

 	set_fan_speeds(fp);
 }

 int bbc_envctrl_init(void)
 {
 	struct linux_ebus_child *echild;
 	int temp_index = 0;
 	int fan_index = 0;
 	int devidx = 0;

 	while ((echild = bbc_i2c_getdev(devidx++)) != NULL) {
 		if (!strcmp(echild->prom_node->name, "temperature"))
 			attach_one_temp(echild, temp_index++);
 		if (!strcmp(echild->prom_node->name, "fan-control"))
 			attach_one_fan(echild, fan_index++);
 	}
 	if (temp_index != 0 && fan_index != 0) {
 		kenvctrld_task = kthread_run(kenvctrld, NULL, "kenvctrld");
 		if (IS_ERR(kenvctrld_task))
 			return PTR_ERR(kenvctrld_task);
 	}

 	return 0;
 }

 static void destroy_one_temp(struct bbc_cpu_temperature *tp)
 {
 	bbc_i2c_detach(tp->client);
 	kfree(tp);
 }

 static void destroy_one_fan(struct bbc_fan_control *fp)
 {
 	bbc_i2c_detach(fp->client);
 	kfree(fp);
 }

 void bbc_envctrl_cleanup(void)
 {
 	struct bbc_cpu_temperature *tp;
 	struct bbc_fan_control *fp;

 	kthread_stop(kenvctrld_task);

 	tp = all_bbc_temps;
 	while (tp != NULL) {
 		struct bbc_cpu_temperature *next = tp->next;
 		destroy_one_temp(tp);
 		tp = next;
 	}
 	all_bbc_temps = NULL;

 	fp = all_bbc_fans;
 	while (fp != NULL) {
 		struct bbc_fan_control *next = fp->next;
 		destroy_one_fan(fp);
 		fp = next;
 	}
 	all_bbc_fans = NULL;
 }
	/* $Id: bbc_envctrl.c,v 1.4 2001/04/06 16:48:08 davem Exp $
	* bbc_envctrl.c: UltraSPARC-III environment control driver.
	*
	* Copyright (C) 2001 David S. Miller (davem@redhat.com)
	*/

	#include <linux/kthread.h>
	#include <linux/delay.h>
	#include <linux/kmod.h>
	#include <linux/reboot.h>
	#include <asm/oplib.h>
	#include <asm/ebus.h>

	#include "bbc_i2c.h"
	#include "max1617.h"

	#undef ENVCTRL_TRACE

	/* WARNING: Making changes to this driver is very dangerous.
	* If you misprogram the sensor chips they can
	* cut the power on you instantly.
	*/

	/* Two temperature sensors exist in the SunBLADE-1000 enclosure.
	* Both are implemented using max1617 i2c devices. Each max1617
	* monitors 2 temperatures, one for one of the cpu dies and the other
	* for the ambient temperature.
	*
	* The max1617 is capable of being programmed with power-off
	* temperature values, one low limit and one high limit. These
	* can be controlled independently for the cpu or ambient temperature.
	* If a limit is violated, the power is simply shut off. The frequency
	* with which the max1617 does temperature sampling can be controlled
	* as well.
	*
	* Three fans exist inside the machine, all three are controlled with
	* an i2c digital to analog converter. There is a fan directed at the
	* two processor slots, another for the rest of the enclosure, and the
	* third is for the power supply. The first two fans may be speed
	* controlled by changing the voltage fed to them. The third fan may
	* only be completely off or on. The third fan is meant to only be
	* disabled/enabled when entering/exiting the lowest power-saving
	* mode of the machine.
	*
	* An environmental control kernel thread periodically monitors all
	* temperature sensors. Based upon the samples it will adjust the
	* fan speeds to try and keep the system within a certain temperature
	* range (the goal being to make the fans as quiet as possible without
	* allowing the system to get too hot).
	*
	* If the temperature begins to rise/fall outside of the acceptable
	* operating range, a periodic warning will be sent to the kernel log.
	* The fans will be put on full blast to attempt to deal with this
	* situation. After exceeding the acceptable operating range by a
	* certain threshold, the kernel thread will shut down the system.
	* Here, the thread is attempting to shut the machine down cleanly
	* before the hardware based power-off event is triggered.
	*/

	/* These settings are in Celsius. We use these defaults only
	* if we cannot interrogate the cpu-fru SEEPROM.
	*/
	struct temp_limits {
	s8 high_pwroff, high_shutdown, high_warn;
	s8 low_warn, low_shutdown, low_pwroff;
	};

	static struct temp_limits cpu_temp_limits[2] = {
	{ 100, 85, 80, 5, -5, -10 },
	{ 100, 85, 80, 5, -5, -10 },
	};

	static struct temp_limits amb_temp_limits[2] = {
	{ 65, 55, 40, 5, -5, -10 },
	{ 65, 55, 40, 5, -5, -10 },
	};

	enum fan_action { FAN_SLOWER, FAN_SAME, FAN_FASTER, FAN_FULLBLAST, FAN_STATE_MAX };

	struct bbc_cpu_temperature {
	struct bbc_cpu_temperature *next;

	struct bbc_i2c_client *client;
	int index;

	/* Current readings, and history. */
	s8 curr_cpu_temp;
	s8 curr_amb_temp;
	s8 prev_cpu_temp;
	s8 prev_amb_temp;
	s8 avg_cpu_temp;
	s8 avg_amb_temp;

	int sample_tick;

	enum fan_action fan_todo[2];
	#define FAN_AMBIENT 0
	#define FAN_CPU 1
	};

	struct bbc_cpu_temperature *all_bbc_temps;

	struct bbc_fan_control {
	struct bbc_fan_control *next;

	struct bbc_i2c_client *client;
	int index;

	int psupply_fan_on;
	int cpu_fan_speed;
	int system_fan_speed;
	};

	struct bbc_fan_control *all_bbc_fans;

	#define CPU_FAN_REG 0xf0
	#define SYS_FAN_REG 0xf2
	#define PSUPPLY_FAN_REG 0xf4

	#define FAN_SPEED_MIN 0x0c
	#define FAN_SPEED_MAX 0x3f

	#define PSUPPLY_FAN_ON 0x1f
	#define PSUPPLY_FAN_OFF 0x00

	static void set_fan_speeds(struct bbc_fan_control *fp)
	{
	/* Put temperatures into range so we don't mis-program
	* the hardware.
	*/
	if (fp->cpu_fan_speed < FAN_SPEED_MIN)
	fp->cpu_fan_speed = FAN_SPEED_MIN;
	if (fp->cpu_fan_speed > FAN_SPEED_MAX)
	fp->cpu_fan_speed = FAN_SPEED_MAX;
	if (fp->system_fan_speed < FAN_SPEED_MIN)
	fp->system_fan_speed = FAN_SPEED_MIN;
	if (fp->system_fan_speed > FAN_SPEED_MAX)
	fp->system_fan_speed = FAN_SPEED_MAX;
	#ifdef ENVCTRL_TRACE
	printk("fan%d: Changed fan speed to cpu(%02x) sys(%02x)\n",
	fp->index,
	fp->cpu_fan_speed, fp->system_fan_speed);
	#endif

	bbc_i2c_writeb(fp->client, fp->cpu_fan_speed, CPU_FAN_REG);
	bbc_i2c_writeb(fp->client, fp->system_fan_speed, SYS_FAN_REG);
	bbc_i2c_writeb(fp->client,
	(fp->psupply_fan_on ?
	PSUPPLY_FAN_ON : PSUPPLY_FAN_OFF),
	PSUPPLY_FAN_REG);
	}

	static void get_current_temps(struct bbc_cpu_temperature *tp)
	{
	tp->prev_amb_temp = tp->curr_amb_temp;
	bbc_i2c_readb(tp->client,
	(unsigned char *) &tp->curr_amb_temp,
	MAX1617_AMB_TEMP);
	tp->prev_cpu_temp = tp->curr_cpu_temp;
	bbc_i2c_readb(tp->client,
	(unsigned char *) &tp->curr_cpu_temp,
	MAX1617_CPU_TEMP);
	#ifdef ENVCTRL_TRACE
	printk("temp%d: cpu(%d C) amb(%d C)\n",
	tp->index,
	(int) tp->curr_cpu_temp, (int) tp->curr_amb_temp);
	#endif
	}


	static void do_envctrl_shutdown(struct bbc_cpu_temperature *tp)
	{
	static int shutting_down = 0;
	char *type = "???";
	s8 val = -1;

	if (shutting_down != 0)
	return;

	if (tp->curr_amb_temp >= amb_temp_limits[tp->index].high_shutdown \|\|
	tp->curr_amb_temp < amb_temp_limits[tp->index].low_shutdown) {
	type = "ambient";
	val = tp->curr_amb_temp;
	} else if (tp->curr_cpu_temp >= cpu_temp_limits[tp->index].high_shutdown \|\|
	tp->curr_cpu_temp < cpu_temp_limits[tp->index].low_shutdown) {
	type = "CPU";
	val = tp->curr_cpu_temp;
	}

	printk(KERN_CRIT "temp%d: Outside of safe %s "
	"operating temperature, %d C.\n",
	tp->index, type, val);

	printk(KERN_CRIT "kenvctrld: Shutting down the system now.\n");

	shutting_down = 1;
	if (orderly_poweroff(true) < 0)
	printk(KERN_CRIT "envctrl: shutdown execution failed\n");
	}

	#define WARN_INTERVAL (30 * HZ)

	static void analyze_ambient_temp(struct bbc_cpu_temperature tp, unsigned long last_warn, int tick)
	{
	int ret = 0;

	if (time_after(jiffies, (*last_warn + WARN_INTERVAL))) {
	if (tp->curr_amb_temp >=
	amb_temp_limits[tp->index].high_warn) {
	printk(KERN_WARNING "temp%d: "
	"Above safe ambient operating temperature, %d C.\n",
	tp->index, (int) tp->curr_amb_temp);
	ret = 1;
	} else if (tp->curr_amb_temp <
	amb_temp_limits[tp->index].low_warn) {
	printk(KERN_WARNING "temp%d: "
	"Below safe ambient operating temperature, %d C.\n",
	tp->index, (int) tp->curr_amb_temp);
	ret = 1;
	}
	if (ret)
	*last_warn = jiffies;
	} else if (tp->curr_amb_temp >= amb_temp_limits[tp->index].high_warn \|\|
	tp->curr_amb_temp < amb_temp_limits[tp->index].low_warn)
	ret = 1;

	/* Now check the shutdown limits. */
	if (tp->curr_amb_temp >= amb_temp_limits[tp->index].high_shutdown \|\|
	tp->curr_amb_temp < amb_temp_limits[tp->index].low_shutdown) {
	do_envctrl_shutdown(tp);
	ret = 1;
	}

	if (ret) {
	tp->fan_todo[FAN_AMBIENT] = FAN_FULLBLAST;
	} else if ((tick & (8 - 1)) == 0) {
	s8 amb_goal_hi = amb_temp_limits[tp->index].high_warn - 10;
	s8 amb_goal_lo;

	amb_goal_lo = amb_goal_hi - 3;

	/* We do not try to avoid 'too cold' events. Basically we
	* only try to deal with over-heating and fan noise reduction.
	*/
	if (tp->avg_amb_temp < amb_goal_hi) {
	if (tp->avg_amb_temp >= amb_goal_lo)
	tp->fan_todo[FAN_AMBIENT] = FAN_SAME;
	else
	tp->fan_todo[FAN_AMBIENT] = FAN_SLOWER;
	} else {
	tp->fan_todo[FAN_AMBIENT] = FAN_FASTER;
	}
	} else {
	tp->fan_todo[FAN_AMBIENT] = FAN_SAME;
	}
	}

	static void analyze_cpu_temp(struct bbc_cpu_temperature tp, unsigned long last_warn, int tick)
	{
	int ret = 0;

	if (time_after(jiffies, (*last_warn + WARN_INTERVAL))) {
	if (tp->curr_cpu_temp >=
	cpu_temp_limits[tp->index].high_warn) {
	printk(KERN_WARNING "temp%d: "
	"Above safe CPU operating temperature, %d C.\n",
	tp->index, (int) tp->curr_cpu_temp);
	ret = 1;
	} else if (tp->curr_cpu_temp <
	cpu_temp_limits[tp->index].low_warn) {
	printk(KERN_WARNING "temp%d: "
	"Below safe CPU operating temperature, %d C.\n",
	tp->index, (int) tp->curr_cpu_temp);
	ret = 1;
	}
	if (ret)
	*last_warn = jiffies;
	} else if (tp->curr_cpu_temp >= cpu_temp_limits[tp->index].high_warn \|\|
	tp->curr_cpu_temp < cpu_temp_limits[tp->index].low_warn)
	ret = 1;

	/* Now check the shutdown limits. */
	if (tp->curr_cpu_temp >= cpu_temp_limits[tp->index].high_shutdown \|\|
	tp->curr_cpu_temp < cpu_temp_limits[tp->index].low_shutdown) {
	do_envctrl_shutdown(tp);
	ret = 1;
	}

	if (ret) {
	tp->fan_todo[FAN_CPU] = FAN_FULLBLAST;
	} else if ((tick & (8 - 1)) == 0) {
	s8 cpu_goal_hi = cpu_temp_limits[tp->index].high_warn - 10;
	s8 cpu_goal_lo;

	cpu_goal_lo = cpu_goal_hi - 3;

	/* We do not try to avoid 'too cold' events. Basically we
	* only try to deal with over-heating and fan noise reduction.
	*/
	if (tp->avg_cpu_temp < cpu_goal_hi) {
	if (tp->avg_cpu_temp >= cpu_goal_lo)
	tp->fan_todo[FAN_CPU] = FAN_SAME;
	else
	tp->fan_todo[FAN_CPU] = FAN_SLOWER;
	} else {
	tp->fan_todo[FAN_CPU] = FAN_FASTER;
	}
	} else {
	tp->fan_todo[FAN_CPU] = FAN_SAME;
	}
	}

	static void analyze_temps(struct bbc_cpu_temperature tp, unsigned long last_warn)
	{
	tp->avg_amb_temp = (s8)((int)((int)tp->avg_amb_temp + (int)tp->curr_amb_temp) / 2);
	tp->avg_cpu_temp = (s8)((int)((int)tp->avg_cpu_temp + (int)tp->curr_cpu_temp) / 2);

	analyze_ambient_temp(tp, last_warn, tp->sample_tick);
	analyze_cpu_temp(tp, last_warn, tp->sample_tick);

	tp->sample_tick++;
	}

	static enum fan_action prioritize_fan_action(int which_fan)
	{
	struct bbc_cpu_temperature *tp;
	enum fan_action decision = FAN_STATE_MAX;

	/* Basically, prioritize what the temperature sensors
	* recommend we do, and perform that action on all the
	* fans.
	*/
	for (tp = all_bbc_temps; tp; tp = tp->next) {
	if (tp->fan_todo[which_fan] == FAN_FULLBLAST) {
	decision = FAN_FULLBLAST;
	break;
	}
	if (tp->fan_todo[which_fan] == FAN_SAME &&
	decision != FAN_FASTER)
	decision = FAN_SAME;
	else if (tp->fan_todo[which_fan] == FAN_FASTER)
	decision = FAN_FASTER;
	else if (decision != FAN_FASTER &&
	decision != FAN_SAME &&
	tp->fan_todo[which_fan] == FAN_SLOWER)
	decision = FAN_SLOWER;
	}
	if (decision == FAN_STATE_MAX)
	decision = FAN_SAME;

	return decision;
	}

	static int maybe_new_ambient_fan_speed(struct bbc_fan_control *fp)
	{
	enum fan_action decision = prioritize_fan_action(FAN_AMBIENT);
	int ret;

	if (decision == FAN_SAME)
	return 0;

	ret = 1;
	if (decision == FAN_FULLBLAST) {
	if (fp->system_fan_speed >= FAN_SPEED_MAX)
	ret = 0;
	else
	fp->system_fan_speed = FAN_SPEED_MAX;
	} else {
	if (decision == FAN_FASTER) {
	if (fp->system_fan_speed >= FAN_SPEED_MAX)
	ret = 0;
	else
	fp->system_fan_speed += 2;
	} else {
	int orig_speed = fp->system_fan_speed;

	if (orig_speed <= FAN_SPEED_MIN \|\|
	orig_speed <= (fp->cpu_fan_speed - 3))
	ret = 0;
	else
	fp->system_fan_speed -= 1;
	}
	}

	return ret;
	}

	static int maybe_new_cpu_fan_speed(struct bbc_fan_control *fp)
	{
	enum fan_action decision = prioritize_fan_action(FAN_CPU);
	int ret;

	if (decision == FAN_SAME)
	return 0;

	ret = 1;
	if (decision == FAN_FULLBLAST) {
	if (fp->cpu_fan_speed >= FAN_SPEED_MAX)
	ret = 0;
	else
	fp->cpu_fan_speed = FAN_SPEED_MAX;
	} else {
	if (decision == FAN_FASTER) {
	if (fp->cpu_fan_speed >= FAN_SPEED_MAX)
	ret = 0;
	else {
	fp->cpu_fan_speed += 2;
	if (fp->system_fan_speed <
	(fp->cpu_fan_speed - 3))
	fp->system_fan_speed =
	fp->cpu_fan_speed - 3;
	}
	} else {
	if (fp->cpu_fan_speed <= FAN_SPEED_MIN)
	ret = 0;
	else
	fp->cpu_fan_speed -= 1;
	}
	}

	return ret;
	}

	static void maybe_new_fan_speeds(struct bbc_fan_control *fp)
	{
	int new;

	new = maybe_new_ambient_fan_speed(fp);
	new \|= maybe_new_cpu_fan_speed(fp);

	if (new)
	set_fan_speeds(fp);
	}

	static void fans_full_blast(void)
	{
	struct bbc_fan_control *fp;

	/* Since we will not be monitoring things anymore, put
	* the fans on full blast.
	*/
	for (fp = all_bbc_fans; fp; fp = fp->next) {
	fp->cpu_fan_speed = FAN_SPEED_MAX;
	fp->system_fan_speed = FAN_SPEED_MAX;
	fp->psupply_fan_on = 1;
	set_fan_speeds(fp);
	}
	}

	#define POLL_INTERVAL (5 * 1000)
	static unsigned long last_warning_jiffies;
	static struct task_struct *kenvctrld_task;

	static int kenvctrld(void *__unused)
	{
	printk(KERN_INFO "bbc_envctrl: kenvctrld starting...\n");
	last_warning_jiffies = jiffies - WARN_INTERVAL;
	for (;;) {
	struct bbc_cpu_temperature *tp;
	struct bbc_fan_control *fp;

	msleep_interruptible(POLL_INTERVAL);
	if (kthread_should_stop())
	break;

	for (tp = all_bbc_temps; tp; tp = tp->next) {
	get_current_temps(tp);
	analyze_temps(tp, &last_warning_jiffies);
	}
	for (fp = all_bbc_fans; fp; fp = fp->next)
	maybe_new_fan_speeds(fp);
	}
	printk(KERN_INFO "bbc_envctrl: kenvctrld exiting...\n");

	fans_full_blast();

	return 0;
	}

	static void attach_one_temp(struct linux_ebus_child *echild, int temp_idx)
	{
	struct bbc_cpu_temperature *tp;

	tp = kzalloc(sizeof(*tp), GFP_KERNEL);
	if (!tp)
	return;

	tp->client = bbc_i2c_attach(echild);
	if (!tp->client) {
	kfree(tp);
	return;
	}

	tp->index = temp_idx;
	{
	struct bbc_cpu_temperature **tpp = &all_bbc_temps;
	while (*tpp)
	tpp = &((*tpp)->next);
	tp->next = NULL;
	*tpp = tp;
	}

	/* Tell it to convert once every 5 seconds, clear all cfg
	* bits.
	*/
	bbc_i2c_writeb(tp->client, 0x00, MAX1617_WR_CFG_BYTE);
	bbc_i2c_writeb(tp->client, 0x02, MAX1617_WR_CVRATE_BYTE);

	/* Program the hard temperature limits into the chip. */
	bbc_i2c_writeb(tp->client, amb_temp_limits[tp->index].high_pwroff,
	MAX1617_WR_AMB_HIGHLIM);
	bbc_i2c_writeb(tp->client, amb_temp_limits[tp->index].low_pwroff,
	MAX1617_WR_AMB_LOWLIM);
	bbc_i2c_writeb(tp->client, cpu_temp_limits[tp->index].high_pwroff,
	MAX1617_WR_CPU_HIGHLIM);
	bbc_i2c_writeb(tp->client, cpu_temp_limits[tp->index].low_pwroff,
	MAX1617_WR_CPU_LOWLIM);

	get_current_temps(tp);
	tp->prev_cpu_temp = tp->avg_cpu_temp = tp->curr_cpu_temp;
	tp->prev_amb_temp = tp->avg_amb_temp = tp->curr_amb_temp;

	tp->fan_todo[FAN_AMBIENT] = FAN_SAME;
	tp->fan_todo[FAN_CPU] = FAN_SAME;
	}

	static void attach_one_fan(struct linux_ebus_child *echild, int fan_idx)
	{
	struct bbc_fan_control *fp;

	fp = kzalloc(sizeof(*fp), GFP_KERNEL);
	if (!fp)
	return;

	fp->client = bbc_i2c_attach(echild);
	if (!fp->client) {
	kfree(fp);
	return;
	}

	fp->index = fan_idx;

	{
	struct bbc_fan_control **fpp = &all_bbc_fans;
	while (*fpp)
	fpp = &((*fpp)->next);
	fp->next = NULL;
	*fpp = fp;
	}

	/* The i2c device controlling the fans is write-only.
	* So the only way to keep track of the current power
	* level fed to the fans is via software. Choose half
	* power for cpu/system and 'on' fo the powersupply fan
	* and set it now.
	*/
	fp->psupply_fan_on = 1;
	fp->cpu_fan_speed = (FAN_SPEED_MAX - FAN_SPEED_MIN) / 2;
	fp->cpu_fan_speed += FAN_SPEED_MIN;
	fp->system_fan_speed = (FAN_SPEED_MAX - FAN_SPEED_MIN) / 2;
	fp->system_fan_speed += FAN_SPEED_MIN;

	set_fan_speeds(fp);
	}

	int bbc_envctrl_init(void)
	{
	struct linux_ebus_child *echild;
	int temp_index = 0;
	int fan_index = 0;
	int devidx = 0;

	while ((echild = bbc_i2c_getdev(devidx++)) != NULL) {
	if (!strcmp(echild->prom_node->name, "temperature"))
	attach_one_temp(echild, temp_index++);
	if (!strcmp(echild->prom_node->name, "fan-control"))
	attach_one_fan(echild, fan_index++);
	}
	if (temp_index != 0 && fan_index != 0) {
	kenvctrld_task = kthread_run(kenvctrld, NULL, "kenvctrld");
	if (IS_ERR(kenvctrld_task))
	return PTR_ERR(kenvctrld_task);
	}

	return 0;
	}

	static void destroy_one_temp(struct bbc_cpu_temperature *tp)
	{
	bbc_i2c_detach(tp->client);
	kfree(tp);
	}

	static void destroy_one_fan(struct bbc_fan_control *fp)
	{
	bbc_i2c_detach(fp->client);
	kfree(fp);
	}

	void bbc_envctrl_cleanup(void)
	{
	struct bbc_cpu_temperature *tp;
	struct bbc_fan_control *fp;

	kthread_stop(kenvctrld_task);

	tp = all_bbc_temps;
	while (tp != NULL) {
	struct bbc_cpu_temperature *next = tp->next;
	destroy_one_temp(tp);
	tp = next;
	}
	all_bbc_temps = NULL;

	fp = all_bbc_fans;
	while (fp != NULL) {
	struct bbc_fan_control *next = fp->next;
	destroy_one_fan(fp);
	fp = next;
	}
	all_bbc_fans = NULL;
	}