Re: [PATCH 4/5] clocksource/drivers: Add CLINT timer driver
From: Palmer Dabbelt
Date: Thu Jun 04 2020 - 16:40:40 EST
On Thu, 21 May 2020 06:45:43 PDT (-0700), Anup Patel wrote:
The TIME CSR and SBI calls are not available in RISC-V M-mode so we
add CLINT driver for Linux RISC-V M-mode (i.e. RISC-V NoMMU kernel).
Signed-off-by: Anup Patel <anup.patel@xxxxxxx>
---
drivers/clocksource/Kconfig | 10 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-clint.c | 226 ++++++++++++++++++++++++++++++
include/linux/cpuhotplug.h | 1 +
4 files changed, 238 insertions(+)
create mode 100644 drivers/clocksource/timer-clint.c
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 21950d9e3e9d..ea97bf0eb09f 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -659,6 +659,16 @@ config RISCV_TIMER
is accessed via both the SBI and the rdcycle instruction. This is
required for all RISC-V systems.
+config CLINT_TIMER
+ bool "Timer for the RISC-V platform"
+ depends on GENERIC_SCHED_CLOCK && RISCV
Presumably this also depends on RISCV_M_MODE?
+ default y
+ select TIMER_PROBE
+ select TIMER_OF
+ help
+ This option enables the CLINT timer for RISC-V systems. The CLINT
+ driver is usually used for NoMMU RISC-V systems.
+
config CSKY_MP_TIMER
bool "SMP Timer for the C-SKY platform" if COMPILE_TEST
depends on CSKY
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 641ba5383ab5..dca308b5ff98 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -86,6 +86,7 @@ obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
obj-$(CONFIG_X86_NUMACHIP) += numachip.o
obj-$(CONFIG_ATCPIT100_TIMER) += timer-atcpit100.o
obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o
+obj-$(CONFIG_CLINT_TIMER) += timer-clint.o
obj-$(CONFIG_CSKY_MP_TIMER) += timer-mp-csky.o
obj-$(CONFIG_GX6605S_TIMER) += timer-gx6605s.o
obj-$(CONFIG_HYPERV_TIMER) += hyperv_timer.o
diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
new file mode 100644
index 000000000000..7fc4f145da65
--- /dev/null
+++ b/drivers/clocksource/timer-clint.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
+ * CLINT MMIO timer device.
+ */
+
+#define pr_fmt(fmt) "clint: " fmt
+#include <linux/bitops.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/sched_clock.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/irqchip/irq-riscv-intc.h>
+#include <linux/interrupt.h>
+#include <linux/of_irq.h>
+#include <linux/smp.h>
+
+#define CLINT_IPI_OFF 0
+#define CLINT_TIME_CMP_OFF 0x4000
+#define CLINT_TIME_VAL_OFF 0xbff8
+
+/* CLINT manages IPI and Timer for RISC-V M-mode */
+static u32 __iomem *clint_ipi_base;
It seems odd to have IPIs in the timer driver. I know the CLINT handles both
of them, but these really feel like two separate drivers.
+static u64 __iomem *clint_time_cmp;
+static u64 __iomem *clint_time_val;
+static unsigned long clint_freq;
+static unsigned int clint_irq;
+
+static void clint_send_ipi(const unsigned long *hart_mask)
+{
+ u32 hartid;
+
+ for_each_set_bit(hartid, hart_mask, NR_CPUS)
+ writel(1, clint_ipi_base + hartid);
+}
+
+static void clint_clear_ipi(void)
+{
+ writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
+}
+
+static struct riscv_ipi_ops clint_ipi_ops = {
+ .ipi_inject = clint_send_ipi,
+ .ipi_clear = clint_clear_ipi,
+};
+
+#ifdef CONFIG_64BIT
+#define clint_get_cycles() readq_relaxed(clint_time_val)
+#else
+#define clint_get_cycles() readl_relaxed(clint_time_val)
+#define clint_get_cycles_hi() readl_relaxed(((u32 *)clint_time_val) + 1)
+#endif
+
+#ifdef CONFIG_64BIT
+static u64 clint_get_cycles64(void)
+{
+ return clint_get_cycles();
+}
+#else /* CONFIG_64BIT */
+static u64 clint_get_cycles64(void)
+{
+ u32 hi, lo;
+
+ do {
+ hi = clint_get_cycles_hi();
+ lo = clint_get_cycles();
+ } while (hi != clint_get_cycles_hi());
+
+ return ((u64)hi << 32) | lo;
+}
+#endif /* CONFIG_64BIT */
+
+static int clint_clock_next_event(unsigned long delta,
+ struct clock_event_device *ce)
+{
+ void __iomem *r = clint_time_cmp +
+ cpuid_to_hartid_map(smp_processor_id());
+
+ csr_set(CSR_IE, IE_TIE);
+ writeq_relaxed(clint_get_cycles64() + delta, r);
+ return 0;
+}
+
+static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = {
+ .name = "clint_clockevent",
+ .features = CLOCK_EVT_FEAT_ONESHOT,
+ .rating = 100,
+ .set_next_event = clint_clock_next_event,
+};
+
+static u64 clint_rdtime(struct clocksource *cs)
+{
+ return readq_relaxed(clint_time_val);
+}
+
+static u64 notrace clint_sched_clock(void)
+{
+ return readq_relaxed(clint_time_val);
+}
+
+static struct clocksource clint_clocksource = {
+ .name = "clint_clocksource",
+ .rating = 300,
+ .mask = CLOCKSOURCE_MASK(64),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+ .read = clint_rdtime,
+};
+
+static int clint_timer_starting_cpu(unsigned int cpu)
+{
+ struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
+
+ ce->cpumask = cpumask_of(cpu);
+ clockevents_config_and_register(ce, clint_freq, 200, ULONG_MAX);
+
+ enable_percpu_irq(clint_irq, irq_get_trigger_type(clint_irq));
+ return 0;
+}
+
+static int clint_timer_dying_cpu(unsigned int cpu)
+{
+ disable_percpu_irq(clint_irq);
+ return 0;
+}
+
+static irqreturn_t clint_timer_interrupt(int irq, void *dev_id)
+{
+ struct clock_event_device *evdev = this_cpu_ptr(&clint_clock_event);
+
+ csr_clear(CSR_IE, IE_TIE);
+ evdev->event_handler(evdev);
+
+ return IRQ_HANDLED;
+}
+
+static int __init clint_timer_init_dt(struct device_node *np)
+{
+ int rc;
+ u32 i, nr_irqs;
+ void __iomem *base;
+ struct of_phandle_args oirq;
+
+ /*
+ * Ensure that CLINT device interrupts are either RV_IRQ_TIMER or
+ * RV_IRQ_SOFT. If it's anything else then we ignore the device.
+ */
+ nr_irqs = of_irq_count(np);
+ for (i = 0; i < nr_irqs; i++) {
+ if (of_irq_parse_one(np, i, &oirq)) {
+ pr_err("%pOFP: failed to parse irq %d.\n", np, i);
+ continue;
+ }
+
+ if ((oirq.args_count != 1) ||
+ (oirq.args[0] != RV_IRQ_TIMER &&
+ oirq.args[0] != RV_IRQ_SOFT)) {
+ pr_info("%pOFP: invalid irq %d (hwirq %d)\n",
+ np, i, oirq.args[0]);
+ return 0;
+ }
+ }
+
+ oirq.np = riscv_of_intc_domain_node();
+ oirq.args_count = 1;
+ oirq.args[0] = RV_IRQ_TIMER;
+ clint_irq = irq_create_of_mapping(&oirq);
+ if (!clint_irq) {
+ pr_err("%pOFP: could not map hwirq %d\n", np, RV_IRQ_TIMER);
+ return -ENODEV;
+ }
+
+ base = of_iomap(np, 0);
+ if (!base) {
+ pr_err("%pOFP: could not map registers\n", np);
+ return -ENODEV;
+ }
+
+ clint_ipi_base = base + CLINT_IPI_OFF;
+ clint_time_cmp = base + CLINT_TIME_CMP_OFF;
+ clint_time_val = base + CLINT_TIME_VAL_OFF;
+ clint_freq = riscv_timebase;
+
+ pr_info("%pOFP: timer running at %ld Hz\n", np, clint_freq);
+
+ rc = clocksource_register_hz(&clint_clocksource, clint_freq);
+ if (rc) {
+ iounmap(base);
+ pr_err("%pOFP: clocksource register failed [%d]\n", np, rc);
+ return rc;
+ }
+
+ sched_clock_register(clint_sched_clock, 64, clint_freq);
+
+ rc = request_percpu_irq(clint_irq, clint_timer_interrupt,
+ "clint-timer", &clint_clock_event);
+ if (rc) {
+ iounmap(base);
+ pr_err("registering percpu irq failed [%d]\n", rc);
+ return rc;
+ }
+
+ rc = cpuhp_setup_state(CPUHP_AP_CLINT_TIMER_STARTING,
+ "clockevents/clint/timer:starting",
+ clint_timer_starting_cpu,
+ clint_timer_dying_cpu);
+ if (rc) {
+ free_irq(clint_irq, &clint_clock_event);
+ iounmap(base);
+ pr_err("%pOFP: cpuhp setup state failed [%d]\n", np, rc);
+ return rc;
+ }
+
+ riscv_set_ipi_ops(&clint_ipi_ops);
+ clint_clear_ipi();
+
+ return 0;
+}
+
+TIMER_OF_DECLARE(clint_timer, "riscv,clint0", clint_timer_init_dt);
+TIMER_OF_DECLARE(clint_timer1, "sifive,clint-1.0.0", clint_timer_init_dt);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 57b1f8f777d9..52552492c2f2 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -132,6 +132,7 @@ enum cpuhp_state {
CPUHP_AP_MIPS_GIC_TIMER_STARTING,
CPUHP_AP_ARC_TIMER_STARTING,
CPUHP_AP_RISCV_TIMER_STARTING,
+ CPUHP_AP_CLINT_TIMER_STARTING,
CPUHP_AP_CSKY_TIMER_STARTING,
CPUHP_AP_HYPERV_TIMER_STARTING,
CPUHP_AP_KVM_STARTING,