Re: [PATCH v4 4/5] clocksource: timer-riscv: Make timer interrupt as a per-CPU interrupt

From: Anup Patel
Date: Mon Mar 09 2020 - 08:00:16 EST

Fixed Marc's email address.

On Mon, Mar 9, 2020 at 4:33 PM Anup Patel <anup.patel@xxxxxxx> wrote:
>
> 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@xxxxxxx>
> ---
> 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
>