The RISC-V ISA defines a single RTC as well as an SBI oneshot timer.
This timer is present on all RISC-V systems.
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxx>
---
drivers/clocksource/Kconfig | 8 +++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-riscv.c | 118 ++++++++++++++++++++++++++++++++++++++
3 files changed, 127 insertions(+)
create mode 100644 drivers/clocksource/timer-riscv.c
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 545d541ae20e..1c2c6e7c7fab 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -612,4 +612,12 @@ config CLKSRC_ST_LPC
Enable this option to use the Low Power controller timer
as clocksource.
+config CLKSRC_RISCV
+ #bool "Clocksource for the RISC-V platform"
+ def_bool y if RISCV
+ depends on RISCV
+ help
+ This enables a clocksource based on the RISC-V SBI timer, which is
+ built in to all RISC-V systems.
+
endmenu
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 2b5b56a6f00f..408ed9d314dc 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -73,3 +73,4 @@ obj-$(CONFIG_H8300_TMR16) += h8300_timer16.o
obj-$(CONFIG_H8300_TPU) += h8300_tpu.o
obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
obj-$(CONFIG_X86_NUMACHIP) += numachip.o
+obj-$(CONFIG_CLKSRC_RISCV) += timer-riscv.o
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
new file mode 100644
index 000000000000..04ef7b9130b3
--- /dev/null
+++ b/drivers/clocksource/timer-riscv.c
@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, version 2.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/delay.h>
+#include <linux/of.h>
+
+#include <asm/irq.h>
+#include <asm/csr.h>
+#include <asm/sbi.h>
+#include <asm/delay.h>
+
+unsigned long riscv_timebase;
+
+static DEFINE_PER_CPU(struct clock_event_device, clock_event);
+
+static int riscv_timer_set_next_event(unsigned long delta,
+ struct clock_event_device *evdev)
+{
+ sbi_set_timer(get_cycles() + delta);
+ return 0;
+}
+
+static int riscv_timer_set_oneshot(struct clock_event_device *evt)
+{
+ /* no-op; only one mode */
+ return 0;
+}
+
+static int riscv_timer_set_shutdown(struct clock_event_device *evt)
+{
+ /* can't stop the clock! */
+ return 0;
+}
+
+static u64 riscv_rdtime(struct clocksource *cs)
+{
+ return get_cycles();
+}
+
+static struct clocksource riscv_clocksource = {
+ .name = "riscv_clocksource",
+ .rating = 300,
+ .read = riscv_rdtime,
+#ifdef CONFIG_64BITS
+ .mask = CLOCKSOURCE_MASK(64),
+#else
+ .mask = CLOCKSOURCE_MASK(32),
+#endif /* CONFIG_64BITS */
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+void riscv_timer_interrupt(void)
+{
+ int cpu = smp_processor_id();
+ struct clock_event_device *evdev = &per_cpu(clock_event, cpu);
+
+ evdev->event_handler(evdev);
+}
+
+void __init init_clockevent(void)
+{
+ int cpu = smp_processor_id();
+ struct clock_event_device *ce = &per_cpu(clock_event, cpu);
+
+ *ce = (struct clock_event_device){
+ .name = "riscv_timer_clockevent",
+ .features = CLOCK_EVT_FEAT_ONESHOT,
+ .rating = 300,
+ .cpumask = cpumask_of(cpu),
+ .set_next_event = riscv_timer_set_next_event,
+ .set_state_oneshot = riscv_timer_set_oneshot,
+ .set_state_shutdown = riscv_timer_set_shutdown,
+ };
+
+ /* Enable timer interrupts */
+ csr_set(sie, SIE_STIE);
+
+ clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
+}
+
+static unsigned long __init of_timebase(void)
+{
+ struct device_node *cpu;
+ const __be32 *prop;
+
+ cpu = of_find_node_by_path("/cpus");
+ if (cpu) {
+ prop = of_get_property(cpu, "timebase-frequency", NULL);
+ if (prop)
+ return be32_to_cpu(*prop);
+ }
+
+ return 10000000;
+}
+
+void __init time_init(void)
+{
+ riscv_timebase = of_timebase();
+ lpj_fine = riscv_timebase / HZ;
+
+ clocksource_register_hz(&riscv_clocksource, riscv_timebase);
+ init_clockevent();
+}
--
2.13.0
