/*
* temp.c Thermal management for cpu's with Thermal Assist Units
*
* Written by Troy Benjegerdes <hozer@drgw.net>
*
* TODO:
* dynamic power management to limit peak CPU temp (using ICTC)
* calibration???
*
* Silly, crazy ideas: use cpu load (from scheduler) and ICTC to extend battery
* life in portables, and add a 'performance/watt' metric somewhere in /proc
*/
#include <linux/errno.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <asm/io.h>
#include <asm/reg.h>
#include <asm/nvram.h>
#include <asm/cache.h>
#include <asm/8xx_immap.h>
#include <asm/machdep.h>
static struct tau_temp
{
int interrupts;
unsigned char low;
unsigned char high;
unsigned char grew;
} tau[NR_CPUS];
struct timer_list tau_timer;
#undef DEBUG
/* TODO: put these in a /proc interface, with some sanity checks, and maybe
* dynamic adjustment to minimize # of interrupts */
/* configurable values for step size and how much to expand the window when
* we get an interrupt. These are based on the limit that was out of range */
#define step_size 2 /* step size when temp goes out of range */
#define window_expand 1 /* expand the window by this much */
/* configurable values for shrinking the window */
#define shrink_timer 2*HZ /* period between shrinking the window */
#define min_window 2 /* minimum window size, degrees C */
void set_thresholds(unsigned long cpu)
{
#ifdef CONFIG_TAU_INT
/*
* setup THRM1,
* threshold, valid bit, enable interrupts, interrupt when below threshold
*/
mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
/* setup THRM2,
* threshold, valid bit, enable interrupts, interrupt when above threshhold
*/
mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
#else
/* same thing but don't enable interrupts */
mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
#endif
}
void TAUupdate(int cpu)
{
unsigned thrm;
#ifdef DEBUG
printk("TAUupdate ");
#endif
/* if both thresholds are crossed, the step_sizes cancel out
* and the window winds up getting expanded twice. */
if((thrm = mfspr(SPRN_THRM1)) & THRM1_TIV){ /* is valid? */
if(thrm & THRM1_TIN){ /* crossed low threshold */
if (tau[cpu].low >= step_size){
tau[cpu].low -= step_size;
tau[cpu].high -= (step_size - window_expand);
}
tau[cpu].grew = 1;
#ifdef DEBUG
printk("low threshold crossed ");
#endif
}
}
if((thrm = mfspr(SPRN_THRM2)) & THRM1_TIV){ /* is valid? */
if(thrm & THRM1_TIN){ /* crossed high threshold */
if (tau[cpu].high <= 127-step_size){
tau[cpu].low += (step_size - window_expand);
tau[cpu].high += step_size;
}
tau[cpu].grew = 1;
#ifdef DEBUG
printk("high threshold crossed ");
#endif
}
}
#ifdef DEBUG
printk("grew = %d\n", tau[cpu].grew);
#endif
#ifndef CONFIG_TAU_INT /* tau_timeout will do this if not using interrupts */
set_thresholds(cpu);
#endif
}
#ifdef CONFIG_TAU_INT
/*
* TAU interrupts - called when we have a thermal assist unit interrupt
* with interrupts disabled
*/
void TAUException(struct pt_regs * regs)
{
int cpu = smp_processor_id();
irq_enter();
tau[cpu].interrupts++;
TAUupdate(cpu);
irq_exit();
}
#endif /* CONFIG_TAU_INT */
static void tau_timeout(void * info)
{
int cpu;
unsigned long flags;
int size;
int shrink;
/* disabling interrupts *should* be okay */
local_irq_save(flags);
cpu = smp_processor_id();
#ifndef CONFIG_TAU_INT
TAUupdate(cpu);
#endif
size = tau[cpu].high - tau[cpu].low;
if (size > min_window && ! tau[cpu].grew) {
/* do an exponential shrink of half the amount currently over size */
shrink = (2 + size - min_window) / 4;
if (shrink) {
tau[cpu].low += shrink;
tau[cpu].high -= shrink;
} else { /* size must have been min_window + 1 */
tau[cpu].low += 1;
#if 1 /* debug */
if ((tau[cpu].high - tau[cpu].low) != min_window){
printk(KERN_ERR "temp.c: line %d, logic error\n", __LINE__);
}
#endif
}
}
tau[cpu].grew = 0;
set_thresholds(cpu);
/*
* Do the enable every time, since otherwise a bunch of (relatively)
* complex sleep code needs to be added. One mtspr every time
* tau_timeout is called is probably not a big deal.
*
* Enable thermal sensor and set up sample interval timer
* need 20 us to do the compare.. until a nice 'cpu_speed' function
* call is implemented, just assume a 500 mhz clock. It doesn't really
* matter if we take too long for a compare since it's all interrupt
* driven anyway.
*
* use a extra long time.. (60 us @ 500 mhz)
*/
mtspr(SPRN_THRM3, THRM3_SITV(500*60) | THRM3_E);
local_irq_restore(flags);
}
static void tau_timeout_smp(unsigned long unused)
{
/* schedule ourselves to be run again */
mod_timer(&tau_timer, jiffies + shrink_timer) ;
on_each_cpu(tau_timeout, NULL, 0);
}
/*
* setup the TAU
*
* Set things up to use THRM1 as a temperature lower bound, and THRM2 as an upper bound.
* Start off at zero
*/
int tau_initialized = 0;
void __init TAU_init_smp(void * info)
{
unsigned long cpu = smp_processor_id();
/* set these to a reasonable value and let the timer shrink the
* window */
tau[cpu].low = 5;
tau[cpu].high = 120;
set_thresholds(cpu);
}
int __init TAU_init(void)
{
/* We assume in SMP that if one CPU has TAU support, they
* all have it --BenH
*/
if (!cpu_has_feature(CPU_FTR_TAU)) {
printk("Thermal assist unit not available\n");
tau_initialized = 0;
return 1;
}
/* first, set up the window shrinking timer */
init_timer(&tau_timer);
tau_timer.function = tau_timeout_smp;
tau_timer.expires = jiffies + shrink_timer;
add_timer(&tau_timer);
on_each_cpu(TAU_init_smp, NULL, 0);
printk("Thermal assist unit ");
#ifdef CONFIG_TAU_INT
printk("using interrupts, ");
#else
printk("using timers, ");
#endif
printk("shrink_timer: %d jiffies\n", shrink_timer);
tau_initialized = 1;
return 0;
}
__initcall(TAU_init);
/*
* return current temp
*/
u32 cpu_temp_both(unsigned long cpu)
{
return ((tau[cpu].high << 16) | tau[cpu].low);
}
int cpu_temp(unsigned long cpu)
{
return ((tau[cpu].high + tau[cpu].low) / 2);
}
int tau_interrupts(unsigned long cpu)
{
return (tau[cpu].interrupts);
}
