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Diffstat (limited to 'arch/powerpc/kernel/tau_6xx.c')
-rw-r--r-- | arch/powerpc/kernel/tau_6xx.c | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c new file mode 100644 index 0000000000..cba6dd15de --- /dev/null +++ b/arch/powerpc/kernel/tau_6xx.c @@ -0,0 +1,237 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * 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/kernel.h> +#include <linux/param.h> +#include <linux/string.h> +#include <linux/mm.h> +#include <linux/interrupt.h> +#include <linux/init.h> +#include <linux/delay.h> +#include <linux/workqueue.h> + +#include <asm/interrupt.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> + +#include "setup.h" + +static struct tau_temp +{ + int interrupts; + unsigned char low; + unsigned char high; + unsigned char grew; +} tau[NR_CPUS]; + +static bool tau_int_enable; + +/* 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 2000 /* period between shrinking the window */ +#define min_window 2 /* minimum window size, degrees C */ + +static void set_thresholds(unsigned long cpu) +{ + u32 maybe_tie = tau_int_enable ? THRM1_TIE : 0; + + /* setup THRM1, threshold, valid bit, interrupt when below threshold */ + mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | maybe_tie | THRM1_TID); + + /* setup THRM2, threshold, valid bit, interrupt when above threshold */ + mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | maybe_tie); +} + +static void TAUupdate(int cpu) +{ + u32 thrm; + u32 bits = THRM1_TIV | THRM1_TIN | THRM1_V; + + /* if both thresholds are crossed, the step_sizes cancel out + * and the window winds up getting expanded twice. */ + thrm = mfspr(SPRN_THRM1); + if ((thrm & bits) == bits) { + mtspr(SPRN_THRM1, 0); + + if (tau[cpu].low >= step_size) { + tau[cpu].low -= step_size; + tau[cpu].high -= (step_size - window_expand); + } + tau[cpu].grew = 1; + pr_debug("%s: low threshold crossed\n", __func__); + } + thrm = mfspr(SPRN_THRM2); + if ((thrm & bits) == bits) { + mtspr(SPRN_THRM2, 0); + + if (tau[cpu].high <= 127 - step_size) { + tau[cpu].low += (step_size - window_expand); + tau[cpu].high += step_size; + } + tau[cpu].grew = 1; + pr_debug("%s: high threshold crossed\n", __func__); + } +} + +#ifdef CONFIG_TAU_INT +/* + * TAU interrupts - called when we have a thermal assist unit interrupt + * with interrupts disabled + */ + +DEFINE_INTERRUPT_HANDLER_ASYNC(TAUException) +{ + int cpu = smp_processor_id(); + + tau[cpu].interrupts++; + + TAUupdate(cpu); +} +#endif /* CONFIG_TAU_INT */ + +static void tau_timeout(void * info) +{ + int cpu; + int size; + int shrink; + + cpu = smp_processor_id(); + + if (!tau_int_enable) + TAUupdate(cpu); + + /* Stop thermal sensor comparisons and interrupts */ + mtspr(SPRN_THRM3, 0); + + 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); + + /* Restart thermal sensor comparisons and interrupts. + * The "PowerPC 740 and PowerPC 750 Microprocessor Datasheet" + * recommends that "the maximum value be set in THRM3 under all + * conditions." + */ + mtspr(SPRN_THRM3, THRM3_SITV(0x1fff) | THRM3_E); +} + +static struct workqueue_struct *tau_workq; + +static void tau_work_func(struct work_struct *work) +{ + msleep(shrink_timer); + on_each_cpu(tau_timeout, NULL, 0); + /* schedule ourselves to be run again */ + queue_work(tau_workq, work); +} + +static DECLARE_WORK(tau_work, tau_work_func); + +/* + * 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; + +static 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); +} + +static 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; + } + + tau_int_enable = IS_ENABLED(CONFIG_TAU_INT) && + !strcmp(cur_cpu_spec->platform, "ppc750"); + + tau_workq = alloc_ordered_workqueue("tau", 0); + if (!tau_workq) + return -ENOMEM; + + on_each_cpu(TAU_init_smp, NULL, 0); + + queue_work(tau_workq, &tau_work); + + pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n", + tau_int_enable ? "interrupts" : "workqueue", 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); +} + +u32 cpu_temp(unsigned long cpu) +{ + return ((tau[cpu].high + tau[cpu].low) / 2); +} + +u32 tau_interrupts(unsigned long cpu) +{ + return (tau[cpu].interrupts); +} |