[PATCH v2 09/12] clocksource: add J-Core PIT/RTC driver

[Rich Felker <dalias@libc.org>]

Signed-off-by: Rich Felker <dalias@libc.org>
---
My previous post of the patch series accidentally omitted omitted
Cc'ing of subsystem maintainers for the necessary clocksource,
irqchip, and spi drivers. Please ack if this looks ok because I want
to get it merged as part of the arch/sh pull request for 4.7.

 drivers/clocksource/Kconfig     |   9 ++
 drivers/clocksource/Makefile    |   1 +
 drivers/clocksource/jcore-pit.c | 176 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 186 insertions(+)
 create mode 100644 drivers/clocksource/jcore-pit.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index c346be6..a29fd31 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -297,6 +297,15 @@ config SYS_SUPPORTS_SH_TMU
 config SYS_SUPPORTS_EM_STI
         bool
 
+config CLKSRC_JCORE_PIT
+	bool "J-Core integrated PIT/RTC"
+	depends on GENERIC_CLOCKEVENTS
+	depends on HAS_IOMEM
+	help
+	  This enables build of clocksource and clockevent driver for
+	  the integrated PIT/RTC in the J-Core synthesizable, open source
+	  SoC.
+
 config SH_TIMER_CMT
 	bool "Renesas CMT timer driver" if COMPILE_TEST
 	depends on GENERIC_CLOCKEVENTS
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index dc2b899..d825fcf 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -5,6 +5,7 @@ obj-$(CONFIG_ATMEL_TCB_CLKSRC)	+= tcb_clksrc.o
 obj-$(CONFIG_X86_PM_TIMER)	+= acpi_pm.o
 obj-$(CONFIG_SCx200HR_TIMER)	+= scx200_hrt.o
 obj-$(CONFIG_CS5535_CLOCK_EVENT_SRC)	+= cs5535-clockevt.o
+obj-$(CONFIG_CLKSRC_JCORE_PIT)		+= jcore-pit.o
 obj-$(CONFIG_SH_TIMER_CMT)	+= sh_cmt.o
 obj-$(CONFIG_SH_TIMER_MTU2)	+= sh_mtu2.o
 obj-$(CONFIG_SH_TIMER_TMU)	+= sh_tmu.o
diff --git a/drivers/clocksource/jcore-pit.c b/drivers/clocksource/jcore-pit.c
new file mode 100644
index 0000000..a4fde51
--- /dev/null
+++ b/drivers/clocksource/jcore-pit.c
@@ -0,0 +1,176 @@
+/*
+ * J-Core SoC PIT/RTC 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/sched.h>
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/interrupt.h>
+#include <linux/profile.h>
+#include <linux/init.h>
+#include <linux/irq.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/cpu.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/irqchip.h>
+#include <asm/io.h>
+#include <asm/irq.h>
+#include <asm/rtc.h>
+
+static unsigned char __iomem *pit_base;
+static int pit_irq;
+static u32 percpu_offset;
+static u32 enable_val;
+
+static struct clock_event_device __percpu *pit_percpu;
+
+#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
+
+static cycle_t rtc_read(struct clocksource *cs)
+{
+	u32 sechi, seclo, nsec, sechi0, seclo0;
+
+	sechi = __raw_readl(pit_base + REG_SECHI);
+	seclo = __raw_readl(pit_base + REG_SECLO);
+	do {
+		sechi0 = sechi;
+		seclo0 = seclo;
+		nsec  = __raw_readl(pit_base + REG_NSEC);
+		sechi = __raw_readl(pit_base + REG_SECHI);
+		seclo = __raw_readl(pit_base + REG_SECLO);
+	} while (sechi0 != sechi || seclo0 != seclo);
+
+	return ((u64)sechi << 32 | seclo) * 1000000000 + nsec;
+}
+
+struct clocksource rtc_csd = {
+	.name = "rtc",
+	.rating = 400,
+	.read = rtc_read,
+	.mult = 1,
+	.shift = 0,
+	.mask = CLOCKSOURCE_MASK(64),
+	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int pit_disable(struct clock_event_device *ced)
+{
+	unsigned cpu = smp_processor_id();
+	writel(0, pit_base + percpu_offset*cpu + REG_PITEN);
+	return 0;
+}
+
+static int pit_set(unsigned long delta, struct clock_event_device *ced)
+{
+	unsigned cpu = smp_processor_id();
+
+	pit_disable(ced);
+
+	writel(delta, pit_base + percpu_offset*cpu + REG_THROT);
+	writel(enable_val, pit_base + percpu_offset*cpu + REG_PITEN);
+
+	return 0;
+}
+
+static int pit_set_periodic(struct clock_event_device *ced)
+{
+	unsigned cpu = smp_processor_id();
+	unsigned long per = readl(pit_base + percpu_offset*cpu + REG_BUSPD);
+
+	return pit_set(DIV_ROUND_CLOSEST(1000000000, HZ*per), ced);
+}
+
+static int pit_local_init(struct clock_event_device *ced)
+{
+	unsigned cpu = smp_processor_id();
+	unsigned long per = readl(pit_base + percpu_offset*cpu + REG_BUSPD);
+
+	pr_info("Local PIT init on cpu %u\n", cpu);
+
+	ced->name = "pit";
+	ced->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT
+		| CLOCK_EVT_FEAT_PERCPU;
+	ced->cpumask = cpumask_of(cpu);
+	ced->rating = 400;
+	ced->irq = pit_irq;
+	ced->set_state_shutdown = pit_disable;
+	ced->set_state_periodic = pit_set_periodic;
+	ced->set_state_oneshot = pit_disable;
+	ced->set_next_event = pit_set;
+
+	clockevents_config_and_register(ced, DIV_ROUND_CLOSEST(1000000000, per),
+	                                1, 0xffffffff);
+
+	pit_set_periodic(ced);
+
+	return 0;
+}
+
+static int pit_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
+{
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_STARTING:
+		pit_local_init(this_cpu_ptr(pit_percpu));
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block pit_cpu_nb = {
+	.notifier_call = pit_cpu_notify,
+};
+
+static irqreturn_t timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *ced = this_cpu_ptr(dev_id);
+
+	if (clockevent_state_oneshot(ced)) pit_disable(ced);
+
+	ced->event_handler(ced);
+
+	return IRQ_HANDLED;
+}
+
+static void __init pit_init(struct device_node *node)
+{
+	unsigned long hwirq;
+	int err;
+
+	pit_base = of_iomap(node, 0);
+	pit_irq = irq_of_parse_and_map(node, 0);
+	of_property_read_u32(node, "cpu-offset", &percpu_offset);
+
+	pr_info("Initializing J-Core PIT at %p IRQ %d\n", pit_base, pit_irq);
+
+	clocksource_register_hz(&rtc_csd, 1000000000);
+
+	pit_percpu = alloc_percpu(struct clock_event_device);
+	register_cpu_notifier(&pit_cpu_nb);
+
+	err = request_irq(pit_irq, timer_interrupt,
+		IRQF_TIMER | IRQF_PERCPU, "pit", pit_percpu);
+	if (err) pr_err("pit irq request failed: %d\n", err);
+
+	hwirq = irq_get_irq_data(pit_irq)->hwirq;
+	enable_val = (1<<26) | ((hwirq&0x3c)<<18) | (hwirq<<12);
+
+	pit_local_init(this_cpu_ptr(pit_percpu));
+}
+
+CLOCKSOURCE_OF_DECLARE(jcore_pit, "jcore,pit", pit_init);
-- 
2.8.1