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-rw-r--r--arch/mips/sni/time.c167
1 files changed, 167 insertions, 0 deletions
diff --git a/arch/mips/sni/time.c b/arch/mips/sni/time.c
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+++ b/arch/mips/sni/time.c
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+// SPDX-License-Identifier: GPL-2.0
+#include <linux/types.h>
+#include <linux/i8253.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/smp.h>
+#include <linux/time.h>
+#include <linux/clockchips.h>
+
+#include <asm/sni.h>
+#include <asm/time.h>
+
+#define SNI_CLOCK_TICK_RATE 3686400
+#define SNI_COUNTER2_DIV 64
+#define SNI_COUNTER0_DIV ((SNI_CLOCK_TICK_RATE / SNI_COUNTER2_DIV) / HZ)
+
+static int a20r_set_periodic(struct clock_event_device *evt)
+{
+ *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0x34;
+ wmb();
+ *(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV & 0xff;
+ wmb();
+ *(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV >> 8;
+ wmb();
+
+ *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0xb4;
+ wmb();
+ *(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV & 0xff;
+ wmb();
+ *(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV >> 8;
+ wmb();
+ return 0;
+}
+
+static struct clock_event_device a20r_clockevent_device = {
+ .name = "a20r-timer",
+ .features = CLOCK_EVT_FEAT_PERIODIC,
+
+ /* .mult, .shift, .max_delta_ns and .min_delta_ns left uninitialized */
+
+ .rating = 300,
+ .irq = SNI_A20R_IRQ_TIMER,
+ .set_state_periodic = a20r_set_periodic,
+};
+
+static irqreturn_t a20r_interrupt(int irq, void *dev_id)
+{
+ struct clock_event_device *cd = dev_id;
+
+ *(volatile u8 *)A20R_PT_TIM0_ACK = 0;
+ wmb();
+
+ cd->event_handler(cd);
+
+ return IRQ_HANDLED;
+}
+
+/*
+ * a20r platform uses 2 counters to divide the input frequency.
+ * Counter 2 output is connected to Counter 0 & 1 input.
+ */
+static void __init sni_a20r_timer_setup(void)
+{
+ struct clock_event_device *cd = &a20r_clockevent_device;
+ unsigned int cpu = smp_processor_id();
+
+ cd->cpumask = cpumask_of(cpu);
+ clockevents_register_device(cd);
+ if (request_irq(SNI_A20R_IRQ_TIMER, a20r_interrupt,
+ IRQF_PERCPU | IRQF_TIMER, "a20r-timer", cd))
+ pr_err("Failed to register a20r-timer interrupt\n");
+}
+
+#define SNI_8254_TICK_RATE 1193182UL
+
+#define SNI_8254_TCSAMP_COUNTER ((SNI_8254_TICK_RATE / HZ) + 255)
+
+static __init unsigned long dosample(void)
+{
+ u32 ct0, ct1;
+ volatile u8 msb;
+
+ /* Start the counter. */
+ outb_p(0x34, 0x43);
+ outb_p(SNI_8254_TCSAMP_COUNTER & 0xff, 0x40);
+ outb(SNI_8254_TCSAMP_COUNTER >> 8, 0x40);
+
+ /* Get initial counter invariant */
+ ct0 = read_c0_count();
+
+ /* Latch and spin until top byte of counter0 is zero */
+ do {
+ outb(0x00, 0x43);
+ (void) inb(0x40);
+ msb = inb(0x40);
+ ct1 = read_c0_count();
+ } while (msb);
+
+ /* Stop the counter. */
+ outb(0x38, 0x43);
+ /*
+ * Return the difference, this is how far the r4k counter increments
+ * for every 1/HZ seconds. We round off the nearest 1 MHz of master
+ * clock (= 1000000 / HZ / 2).
+ */
+ /*return (ct1 - ct0 + (500000/HZ/2)) / (500000/HZ) * (500000/HZ);*/
+ return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
+}
+
+/*
+ * Here we need to calibrate the cycle counter to at least be close.
+ */
+void __init plat_time_init(void)
+{
+ unsigned long r4k_ticks[3];
+ unsigned long r4k_tick;
+
+ /*
+ * Figure out the r4k offset, the algorithm is very simple and works in
+ * _all_ cases as long as the 8254 counter register itself works ok (as
+ * an interrupt driving timer it does not because of bug, this is why
+ * we are using the onchip r4k counter/compare register to serve this
+ * purpose, but for r4k_offset calculation it will work ok for us).
+ * There are other very complicated ways of performing this calculation
+ * but this one works just fine so I am not going to futz around. ;-)
+ */
+ printk(KERN_INFO "Calibrating system timer... ");
+ dosample(); /* Prime cache. */
+ dosample(); /* Prime cache. */
+ /* Zero is NOT an option. */
+ do {
+ r4k_ticks[0] = dosample();
+ } while (!r4k_ticks[0]);
+ do {
+ r4k_ticks[1] = dosample();
+ } while (!r4k_ticks[1]);
+
+ if (r4k_ticks[0] != r4k_ticks[1]) {
+ printk("warning: timer counts differ, retrying... ");
+ r4k_ticks[2] = dosample();
+ if (r4k_ticks[2] == r4k_ticks[0]
+ || r4k_ticks[2] == r4k_ticks[1])
+ r4k_tick = r4k_ticks[2];
+ else {
+ printk("disagreement, using average... ");
+ r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
+ + r4k_ticks[2]) / 3;
+ }
+ } else
+ r4k_tick = r4k_ticks[0];
+
+ printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
+ (int) (r4k_tick / (500000 / HZ)),
+ (int) (r4k_tick % (500000 / HZ)));
+
+ mips_hpt_frequency = r4k_tick * HZ;
+
+ switch (sni_brd_type) {
+ case SNI_BRD_10:
+ case SNI_BRD_10NEW:
+ case SNI_BRD_TOWER_OASIC:
+ case SNI_BRD_MINITOWER:
+ sni_a20r_timer_setup();
+ break;
+ }
+ setup_pit_timer();
+}