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 000000000..828d0f410
--- /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_workqueue("tau", WQ_UNBOUND, 1);
+	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);
+}