[PATCH v3 2/4] clocksource/drivers: Add CLINT timer driver
Daniel Lezcano
daniel.lezcano at linaro.org
Thu Jul 16 17:27:53 EDT 2020
Hi Anup,
On 15/07/2020 09:15, Anup Patel wrote:
> The TIME CSR and SBI calls are not available in RISC-V M-mode so we
> separate add CLINT driver for Linux RISC-V M-mode (i.e. RISC-V NoMMU
> kernel).
The description is confusing, please reword it and give a bit more
information about the timer itself, especially, the IPI thing.
> Signed-off-by: Anup Patel <anup.patel at wdc.com>
> ---
> drivers/clocksource/Kconfig | 10 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++++++++++++++
> include/linux/cpuhotplug.h | 1 +
> 4 files changed, 241 insertions(+)
> create mode 100644 drivers/clocksource/timer-clint.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 91418381fcd4..eabcf1cfb0c0 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -658,6 +658,16 @@ 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_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.
For the timer, we do silent option and let the platform config select
it. Please refer to other timer option below as reference.
> 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 bdda1a2e4097..18e700e703a0 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -87,6 +87,7 @@ 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..bfc38bb5a589
> --- /dev/null
> +++ b/drivers/clocksource/timer-clint.c
> @@ -0,0 +1,229 @@
> +// 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/interrupt.h>
> +#include <linux/of_irq.h>
> +#include <linux/smp.h>
> +
> +#define CLINT_IPI_OFF 0
> +#define CLINT_TIMER_CMP_OFF 0x4000
> +#define CLINT_TIMER_VAL_OFF 0xbff8
> +
> +/* CLINT manages IPI and Timer for RISC-V M-mode */
> +static u32 __iomem *clint_ipi_base;
> +static u64 __iomem *clint_timer_cmp;
> +static u64 __iomem *clint_timer_val;
> +static unsigned long clint_timer_freq;
> +static unsigned int clint_timer_irq;
> +
> +static void clint_send_ipi(const struct cpumask *target)
> +{
> + unsigned int cpu;
> +
> + for_each_cpu(cpu, target)
> + writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
> +}
> +
> +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_timer_val)
> +#else
> +#define clint_get_cycles() readl_relaxed(clint_timer_val)
> +#define clint_get_cycles_hi() readl_relaxed(((u32 *)clint_timer_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_timer_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_timer_val);
> +}
> +
> +static u64 notrace clint_sched_clock(void)
> +{
> + return readq_relaxed(clint_timer_val);
> +}
> +
> +static struct clocksource clint_clocksource = {
> + .name = "clint_clocksource",
> + .rating = 300,
> + .mask = CLOCKSOURCE_MASK(64),
> + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> + .read = clint_rdtime,
What if !CONFIG_64BIT
> +};
> +
> +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_timer_freq, 200, ULONG_MAX);
The function is not immune against registering the same clockevents. If
the CPU is hotplugged several times, this function will be called again
and again. Why not rely on a for_each_possible_cpu loop in the init
function ?
> + enable_percpu_irq(clint_timer_irq,
> + irq_get_trigger_type(clint_timer_irq));
Why do you want to enable / disable the interrrupts ? The should be
already handle by the hotplug framework no ?
> + return 0;
> +}
> +
> +static int clint_timer_dying_cpu(unsigned int cpu)
> +{
> + disable_percpu_irq(clint_timer_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_err("%pOFP: invalid irq %d (hwirq %d)\n",
> + np, i, oirq.args[0]);
> + return -ENODEV;
> + }
> +
> + /* Find parent irq domain and map timer irq */
> + if (!clint_timer_irq &&
> + oirq.args[0] == RV_IRQ_TIMER &&
> + irq_find_host(oirq.np))
> + clint_timer_irq = irq_of_parse_and_map(np, i);
> + }
> +
> + /* If CLINT timer irq not found then fail */
> + if (!clint_timer_irq) {
> + pr_err("%pOFP: timer irq not found\n", np);
> + 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_timer_cmp = base + CLINT_TIMER_CMP_OFF;
> + clint_timer_val = base + CLINT_TIMER_VAL_OFF;
> + clint_timer_freq = riscv_timebase;
> +
> + pr_info("%pOFP: timer running at %ld Hz\n", np, clint_timer_freq);
> +
> + rc = clocksource_register_hz(&clint_clocksource, clint_timer_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_timer_freq);
> +
> + rc = request_percpu_irq(clint_timer_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_timer_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,clint0", clint_timer_init_dt);
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 191772d4a4d7..1451f4625833 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,
>
--
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