1 files changed, 249 insertions, 0 deletions
diff --git a/drivers/clocksource/jcore-pit.c b/drivers/clocksource/jcore-pit.c
new file mode 100644
index 000000000000..54e1665aa03c
--- /dev/null
+++ b/drivers/clocksource/jcore-pit.c
@@ -0,0 +1,249 @@
+/*
+ * J-Core SoC PIT/clocksource driver
+ *
+ * Copyright (C) 2015-2016 Smart Energy Instruments, Inc.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/sched_clock.h>
+#include <linux/cpu.h>
+#include <linux/cpuhotplug.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+
+#define PIT_IRQ_SHIFT		12
+#define PIT_PRIO_SHIFT		20
+#define PIT_ENABLE_SHIFT	26
+#define PIT_PRIO_MASK		0xf
+
+#define REG_PITEN		0x00
+#define REG_THROT		0x10
+#define REG_COUNT		0x14
+#define REG_BUSPD		0x18
+#define REG_SECHI		0x20
+#define REG_SECLO		0x24
+#define REG_NSEC		0x28
+
+struct jcore_pit {
+	struct clock_event_device	ced;
+	void __iomem			*base;
+	unsigned long			periodic_delta;
+	u32				enable_val;
+};
+
+static void __iomem *jcore_pit_base;
+static struct jcore_pit __percpu *jcore_pit_percpu;
+
+static notrace u64 jcore_sched_clock_read(void)
+{
+	u32 seclo, nsec, seclo0;
+	__iomem void *base = jcore_pit_base;
+
+	seclo = readl(base + REG_SECLO);
+	do {
+		seclo0 = seclo;
+		nsec  = readl(base + REG_NSEC);
+		seclo = readl(base + REG_SECLO);
+	} while (seclo0 != seclo);
+
+	return seclo * NSEC_PER_SEC + nsec;
+}
+
+static cycle_t jcore_clocksource_read(struct clocksource *cs)
+{
+	return jcore_sched_clock_read();
+}
+
+static int jcore_pit_disable(struct jcore_pit *pit)
+{
+	writel(0, pit->base + REG_PITEN);
+	return 0;
+}
+
+static int jcore_pit_set(unsigned long delta, struct jcore_pit *pit)
+{
+	jcore_pit_disable(pit);
+	writel(delta, pit->base + REG_THROT);
+	writel(pit->enable_val, pit->base + REG_PITEN);
+	return 0;
+}
+
+static int jcore_pit_set_state_shutdown(struct clock_event_device *ced)
+{
+	struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
+
+	return jcore_pit_disable(pit);
+}
+
+static int jcore_pit_set_state_oneshot(struct clock_event_device *ced)
+{
+	struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
+
+	return jcore_pit_disable(pit);
+}
+
+static int jcore_pit_set_state_periodic(struct clock_event_device *ced)
+{
+	struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
+
+	return jcore_pit_set(pit->periodic_delta, pit);
+}
+
+static int jcore_pit_set_next_event(unsigned long delta,
+				    struct clock_event_device *ced)
+{
+	struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
+
+	return jcore_pit_set(delta, pit);
+}
+
+static int jcore_pit_local_init(unsigned cpu)
+{
+	struct jcore_pit *pit = this_cpu_ptr(jcore_pit_percpu);
+	unsigned buspd, freq;
+
+	pr_info("Local J-Core PIT init on cpu %u\n", cpu);
+
+	buspd = readl(pit->base + REG_BUSPD);
+	freq = DIV_ROUND_CLOSEST(NSEC_PER_SEC, buspd);
+	pit->periodic_delta = DIV_ROUND_CLOSEST(NSEC_PER_SEC, HZ * buspd);
+
+	clockevents_config_and_register(&pit->ced, freq, 1, ULONG_MAX);
+
+	return 0;
+}
+
+static irqreturn_t jcore_timer_interrupt(int irq, void *dev_id)
+{
+	struct jcore_pit *pit = this_cpu_ptr(dev_id);
+
+	if (clockevent_state_oneshot(&pit->ced))
+		jcore_pit_disable(pit);
+
+	pit->ced.event_handler(&pit->ced);
+
+	return IRQ_HANDLED;
+}
+
+static int __init jcore_pit_init(struct device_node *node)
+{
+	int err;
+	unsigned pit_irq, cpu;
+	unsigned long hwirq;
+	u32 irqprio, enable_val;
+
+	jcore_pit_base = of_iomap(node, 0);
+	if (!jcore_pit_base) {
+		pr_err("Error: Cannot map base address for J-Core PIT\n");
+		return -ENXIO;
+	}
+
+	pit_irq = irq_of_parse_and_map(node, 0);
+	if (!pit_irq) {
+		pr_err("Error: J-Core PIT has no IRQ\n");
+		return -ENXIO;
+	}
+
+	pr_info("Initializing J-Core PIT at %p IRQ %d\n",
+		jcore_pit_base, pit_irq);
+
+	err = clocksource_mmio_init(jcore_pit_base, "jcore_pit_cs",
+				    NSEC_PER_SEC, 400, 32,
+				    jcore_clocksource_read);
+	if (err) {
+		pr_err("Error registering clocksource device: %d\n", err);
+		return err;
+	}
+
+	sched_clock_register(jcore_sched_clock_read, 32, NSEC_PER_SEC);
+
+	jcore_pit_percpu = alloc_percpu(struct jcore_pit);
+	if (!jcore_pit_percpu) {
+		pr_err("Failed to allocate memory for clock event device\n");
+		return -ENOMEM;
+	}
+
+	err = request_irq(pit_irq, jcore_timer_interrupt,
+			  IRQF_TIMER | IRQF_PERCPU,
+			  "jcore_pit", jcore_pit_percpu);
+	if (err) {
+		pr_err("pit irq request failed: %d\n", err);
+		free_percpu(jcore_pit_percpu);
+		return err;
+	}
+
+	/*
+	 * The J-Core PIT is not hard-wired to a particular IRQ, but
+	 * integrated with the interrupt controller such that the IRQ it
+	 * generates is programmable, as follows:
+	 *
+	 * The bit layout of the PIT enable register is:
+	 *
+	 *	.....e..ppppiiiiiiii............
+	 *
+	 * where the .'s indicate unrelated/unused bits, e is enable,
+	 * p is priority, and i is hard irq number.
+	 *
+	 * For the PIT included in AIC1 (obsolete but still in use),
+	 * any hard irq (trap number) can be programmed via the 8
+	 * iiiiiiii bits, and a priority (0-15) is programmable
+	 * separately in the pppp bits.
+	 *
+	 * For the PIT included in AIC2 (current), the programming
+	 * interface is equivalent modulo interrupt mapping. This is
+	 * why a different compatible tag was not used. However only
+	 * traps 64-127 (the ones actually intended to be used for
+	 * interrupts, rather than syscalls/exceptions/etc.) can be
+	 * programmed (the high 2 bits of i are ignored) and the
+	 * priority pppp is <<2'd and or'd onto the irq number. This
+	 * choice seems to have been made on the hardware engineering
+	 * side under an assumption that preserving old AIC1 priority
+	 * mappings was important. Future models will likely ignore
+	 * the pppp field.
+	 */
+	hwirq = irq_get_irq_data(pit_irq)->hwirq;
+	irqprio = (hwirq >> 2) & PIT_PRIO_MASK;
+	enable_val = (1U << PIT_ENABLE_SHIFT)
+		   | (hwirq << PIT_IRQ_SHIFT)
+		   | (irqprio << PIT_PRIO_SHIFT);
+
+	for_each_present_cpu(cpu) {
+		struct jcore_pit *pit = per_cpu_ptr(jcore_pit_percpu, cpu);
+
+		pit->base = of_iomap(node, cpu);
+		if (!pit->base) {
+			pr_err("Unable to map PIT for cpu %u\n", cpu);
+			continue;
+		}
+
+		pit->ced.name = "jcore_pit";
+		pit->ced.features = CLOCK_EVT_FEAT_PERIODIC
+				  | CLOCK_EVT_FEAT_ONESHOT
+				  | CLOCK_EVT_FEAT_PERCPU;
+		pit->ced.cpumask = cpumask_of(cpu);
+		pit->ced.rating = 400;
+		pit->ced.irq = pit_irq;
+		pit->ced.set_state_shutdown = jcore_pit_set_state_shutdown;
+		pit->ced.set_state_periodic = jcore_pit_set_state_periodic;
+		pit->ced.set_state_oneshot = jcore_pit_set_state_oneshot;
+		pit->ced.set_next_event = jcore_pit_set_next_event;
+
+		pit->enable_val = enable_val;
+	}
+
+	cpuhp_setup_state(CPUHP_AP_JCORE_TIMER_STARTING,
+			  "AP_JCORE_TIMER_STARTING",
+			  jcore_pit_local_init, NULL);
+
+	return 0;
+}
+
+CLOCKSOURCE_OF_DECLARE(jcore_pit, "jcore,pit", jcore_pit_init);