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Message-ID: <CAMuHMdXkO-r1kVow-PqyRNYy32Eq5jr9fn75neFcMWhDUvGCPA@mail.gmail.com>
Date: Wed, 7 Jun 2017 09:12:28 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Palmer Dabbelt <palmer@...belt.com>
Cc: Linux-Arch <linux-arch@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
albert@...ive.com, patches@...ups.riscv.org,
Thomas Gleixner <tglx@...utronix.de>,
Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH 09/17] clocksource/timer-riscv: New RISC-V Clocksource
CC clocksource folks
On Wed, Jun 7, 2017 at 12:59 AM, Palmer Dabbelt <palmer@...belt.com> wrote:
> The RISC-V ISA defines a single RTC as well as an SBI oneshot timer.
> This timer is present on all RISC-V systems.
>
> Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
> ---
> drivers/clocksource/Kconfig | 8 +++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-riscv.c | 118 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 127 insertions(+)
> create mode 100644 drivers/clocksource/timer-riscv.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 545d541ae20e..1c2c6e7c7fab 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -612,4 +612,12 @@ config CLKSRC_ST_LPC
> Enable this option to use the Low Power controller timer
> as clocksource.
>
> +config CLKSRC_RISCV
> + #bool "Clocksource for the RISC-V platform"
> + def_bool y if RISCV
> + depends on RISCV
> + help
> + This enables a clocksource based on the RISC-V SBI timer, which is
> + built in to all RISC-V systems.
> +
> endmenu
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 2b5b56a6f00f..408ed9d314dc 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -73,3 +73,4 @@ obj-$(CONFIG_H8300_TMR16) += h8300_timer16.o
> obj-$(CONFIG_H8300_TPU) += h8300_tpu.o
> obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
> obj-$(CONFIG_X86_NUMACHIP) += numachip.o
> +obj-$(CONFIG_CLKSRC_RISCV) += timer-riscv.o
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> new file mode 100644
> index 000000000000..04ef7b9130b3
> --- /dev/null
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -0,0 +1,118 @@
> +/*
> + * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2017 SiFive
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation, version 2.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/delay.h>
> +#include <linux/of.h>
> +
> +#include <asm/irq.h>
> +#include <asm/csr.h>
> +#include <asm/sbi.h>
> +#include <asm/delay.h>
> +
> +unsigned long riscv_timebase;
> +
> +static DEFINE_PER_CPU(struct clock_event_device, clock_event);
> +
> +static int riscv_timer_set_next_event(unsigned long delta,
> + struct clock_event_device *evdev)
> +{
> + sbi_set_timer(get_cycles() + delta);
> + return 0;
> +}
> +
> +static int riscv_timer_set_oneshot(struct clock_event_device *evt)
> +{
> + /* no-op; only one mode */
> + return 0;
> +}
> +
> +static int riscv_timer_set_shutdown(struct clock_event_device *evt)
> +{
> + /* can't stop the clock! */
> + return 0;
> +}
> +
> +static u64 riscv_rdtime(struct clocksource *cs)
> +{
> + return get_cycles();
> +}
> +
> +static struct clocksource riscv_clocksource = {
> + .name = "riscv_clocksource",
> + .rating = 300,
> + .read = riscv_rdtime,
> +#ifdef CONFIG_64BITS
> + .mask = CLOCKSOURCE_MASK(64),
> +#else
> + .mask = CLOCKSOURCE_MASK(32),
> +#endif /* CONFIG_64BITS */
> + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> +};
> +
> +void riscv_timer_interrupt(void)
> +{
> + int cpu = smp_processor_id();
> + struct clock_event_device *evdev = &per_cpu(clock_event, cpu);
> +
> + evdev->event_handler(evdev);
> +}
> +
> +void __init init_clockevent(void)
> +{
> + int cpu = smp_processor_id();
> + struct clock_event_device *ce = &per_cpu(clock_event, cpu);
> +
> + *ce = (struct clock_event_device){
> + .name = "riscv_timer_clockevent",
> + .features = CLOCK_EVT_FEAT_ONESHOT,
> + .rating = 300,
> + .cpumask = cpumask_of(cpu),
> + .set_next_event = riscv_timer_set_next_event,
> + .set_state_oneshot = riscv_timer_set_oneshot,
> + .set_state_shutdown = riscv_timer_set_shutdown,
> + };
> +
> + /* Enable timer interrupts */
> + csr_set(sie, SIE_STIE);
> +
> + clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
> +}
> +
> +static unsigned long __init of_timebase(void)
> +{
> + struct device_node *cpu;
> + const __be32 *prop;
> +
> + cpu = of_find_node_by_path("/cpus");
> + if (cpu) {
> + prop = of_get_property(cpu, "timebase-frequency", NULL);
> + if (prop)
> + return be32_to_cpu(*prop);
> + }
> +
> + return 10000000;
> +}
> +
> +void __init time_init(void)
> +{
> + riscv_timebase = of_timebase();
> + lpj_fine = riscv_timebase / HZ;
> +
> + clocksource_register_hz(&riscv_clocksource, riscv_timebase);
> + init_clockevent();
> +}
> --
> 2.13.0
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