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Subject[PATCH v4 4/5] clocksource: timer-riscv: Make timer interrupt as a per-CPU interrupt
Date
Instead of directly calling RISC-V timer interrupt handler from
RISC-V local interrupt conntroller driver, this patch implements
RISC-V timer interrupt as a per-CPU interrupt using per-CPU APIs
of Linux IRQ subsystem.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
arch/riscv/include/asm/irq.h | 2 -
drivers/clocksource/timer-riscv.c | 79 ++++++++++++++++++++-----------
drivers/irqchip/irq-riscv-intc.c | 8 ----
3 files changed, 52 insertions(+), 37 deletions(-)

diff --git a/arch/riscv/include/asm/irq.h b/arch/riscv/include/asm/irq.h
index a9e5f07a7e9c..9807ad164015 100644
--- a/arch/riscv/include/asm/irq.h
+++ b/arch/riscv/include/asm/irq.h
@@ -10,8 +10,6 @@
#include <linux/interrupt.h>
#include <linux/linkage.h>

-void riscv_timer_interrupt(void);
-
#include <asm-generic/irq.h>

#endif /* _ASM_RISCV_IRQ_H */
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index c4f15c4068c0..6b82f2e41f8e 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -14,7 +14,10 @@
#include <linux/irq.h>
#include <linux/sched_clock.h>
#include <linux/io-64-nonatomic-lo-hi.h>
-#include <asm/smp.h>
+#include <linux/irqdomain.h>
+#include <linux/interrupt.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
#include <asm/sbi.h>

u64 __iomem *riscv_time_cmp;
@@ -39,6 +42,7 @@ static int riscv_clock_next_event(unsigned long delta,
return 0;
}

+static unsigned int riscv_clock_event_irq;
static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
.name = "riscv_timer_clockevent",
.features = CLOCK_EVT_FEAT_ONESHOT,
@@ -74,65 +78,86 @@ static int riscv_timer_starting_cpu(unsigned int cpu)
struct clock_event_device *ce = per_cpu_ptr(&riscv_clock_event, cpu);

ce->cpumask = cpumask_of(cpu);
+ ce->irq = riscv_clock_event_irq;
clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);

- csr_set(CSR_IE, IE_TIE);
+ enable_percpu_irq(riscv_clock_event_irq,
+ irq_get_trigger_type(riscv_clock_event_irq));
return 0;
}

static int riscv_timer_dying_cpu(unsigned int cpu)
{
- csr_clear(CSR_IE, IE_TIE);
+ disable_percpu_irq(riscv_clock_event_irq);
return 0;
}

/* called directly from the low-level interrupt handler */
-void riscv_timer_interrupt(void)
+static irqreturn_t riscv_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evdev = this_cpu_ptr(&riscv_clock_event);

csr_clear(CSR_IE, IE_TIE);
evdev->event_handler(evdev);
+
+ return IRQ_HANDLED;
}

static int __init riscv_timer_init_dt(struct device_node *n)
{
- int cpuid, hartid, error;
-
- hartid = riscv_of_processor_hartid(n);
- if (hartid < 0) {
- pr_warn("Not valid hartid for node [%pOF] error = [%d]\n",
- n, hartid);
- return hartid;
- }
-
- cpuid = riscv_hartid_to_cpuid(hartid);
- if (cpuid < 0) {
- pr_warn("Invalid cpuid for hartid [%d]\n", hartid);
- return cpuid;
- }
-
- if (cpuid != smp_processor_id())
+ int error;
+ struct of_phandle_args oirq;
+
+ /*
+ * Either we have one INTC DT node under each CPU DT node
+ * or a single system wide INTC DT node. Irrespective to
+ * number of INTC DT nodes, we only proceed if we are able
+ * to find irq_domain of INTC.
+ *
+ * Once we have INTC irq_domain, we create mapping for timer
+ * interrupt HWIRQ and request_percpu_irq() on it.
+ */
+
+ if (!irq_find_host(n) || riscv_clock_event_irq)
return 0;

- pr_info("%s: Registering clocksource cpuid [%d] hartid [%d]\n",
- __func__, cpuid, hartid);
+ oirq.np = n;
+ oirq.args_count = 1;
+ oirq.args[0] = RV_IRQ_TIMER;
+ riscv_clock_event_irq = irq_create_of_mapping(&oirq);
+ if (!riscv_clock_event_irq)
+ return -ENODEV;
+
error = clocksource_register_hz(&riscv_clocksource, riscv_timebase);
if (error) {
- pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
- error, cpuid);
+ pr_err("registering clocksource failed [%d]\n", error);
return error;
}

sched_clock_register(riscv_sched_clock, 64, riscv_timebase);

+ error = request_percpu_irq(riscv_clock_event_irq,
+ riscv_timer_interrupt,
+ "riscv-timer", &riscv_clock_event);
+ if (error) {
+ pr_err("registering percpu irq failed [%d]\n", error);
+ return error;
+ }
+
error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
"clockevents/riscv/timer:starting",
riscv_timer_starting_cpu, riscv_timer_dying_cpu);
- if (error)
+ if (error) {
pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
error);
- return error;
+ return error;
+ }
+
+ pr_info("running at %lu.%02luMHz frequency\n",
+ (unsigned long)riscv_timebase / 1000000,
+ (unsigned long)(riscv_timebase / 10000) % 100);
+
+ return 0;
}

-TIMER_OF_DECLARE(riscv_timer, "riscv", riscv_timer_init_dt);
+TIMER_OF_DECLARE(riscv_timer, "riscv,cpu-intc", riscv_timer_init_dt);
diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
index e8f7af6dd3c2..93d9d2a38059 100644
--- a/drivers/irqchip/irq-riscv-intc.c
+++ b/drivers/irqchip/irq-riscv-intc.c
@@ -20,20 +20,12 @@ static struct irq_domain *intc_domain;

static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
{
- struct pt_regs *old_regs;
unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;

if (unlikely(cause >= BITS_PER_LONG))
panic("unexpected interrupt cause");

switch (cause) {
- case RV_IRQ_TIMER:
- old_regs = set_irq_regs(regs);
- irq_enter();
- riscv_timer_interrupt();
- irq_exit();
- set_irq_regs(old_regs);
- break;
#ifdef CONFIG_SMP
case RV_IRQ_SOFT:
/*
--
2.17.1
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