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Message-ID: <CAOnJCUKX_+TZR8sMFDL2K4vNRwo0v12Fb5=rX5KUNpRaw8LGsg@mail.gmail.com>
Date: Thu, 28 May 2020 22:04:23 -0700
From: Atish Patra <atishp@...shpatra.org>
To: Anup Patel <anup.patel@....com>
Cc: Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Albert Ou <aou@...s.berkeley.edu>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
Jason Cooper <jason@...edaemon.net>,
Marc Zyngier <maz@...nel.org>,
Anup Patel <anup@...infault.org>,
"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
Atish Patra <atish.patra@....com>,
Alistair Francis <Alistair.Francis@....com>,
linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v5 4/6] clocksource/drivers/timer-riscv: Use per-CPU timer interrupt
On Thu, May 21, 2020 at 6:34 AM Anup Patel <anup.patel@....com> 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@....com>
> ---
> arch/riscv/include/asm/irq.h | 2 --
> drivers/clocksource/timer-riscv.c | 30 +++++++++++++++++++++++++++---
> drivers/irqchip/irq-riscv-intc.c | 8 --------
> 3 files changed, 27 insertions(+), 13 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..5fb7c5ba5c91 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -14,6 +14,9 @@
> #include <linux/irq.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 <asm/smp.h>
> #include <asm/sbi.h>
>
> @@ -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,
> @@ -74,30 +78,35 @@ 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;
> + struct of_phandle_args oirq;
>
> hartid = riscv_of_processor_hartid(n);
> if (hartid < 0) {
> @@ -115,6 +124,13 @@ static int __init riscv_timer_init_dt(struct device_node *n)
> if (cpuid != smp_processor_id())
> return 0;
>
> + oirq.np = riscv_of_intc_domain_node();
> + 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;
> +
As the error case will result in a system without a clock, a warning message
may be a good option.
> pr_info("%s: Registering clocksource cpuid [%d] hartid [%d]\n",
> __func__, cpuid, hartid);
> error = clocksource_register_hz(&riscv_clocksource, riscv_timebase);
> @@ -126,6 +142,14 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>
> 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);
> diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
> index 2f364e6a87f9..d4fbc3543459 100644
> --- a/drivers/irqchip/irq-riscv-intc.c
> +++ b/drivers/irqchip/irq-riscv-intc.c
> @@ -23,20 +23,12 @@ 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:
> /*
> --
> 2.25.1
>
>
Otherwise, LGTM.
Reviewed-by: Atish Patra <atish.patra@....com>
--
Regards,
Atish
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