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Date: Tue, 21 Jul 2020 12:39:22 -0700
From: Atish Patra <atishp@...shpatra.org>
To: Anup Patel <anup@...infault.org>
Cc: Anup Patel <anup.patel@....com>,
Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Albert Ou <aou@...s.berkeley.edu>,
Rob Herring <robh+dt@...nel.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
devicetree@...r.kernel.org, Damien Le Moal <damien.lemoal@....com>,
Emil Renner Berhing <kernel@...il.dk>,
"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 v4 2/4] clocksource/drivers: Add CLINT timer driver
On Tue, Jul 21, 2020 at 4:44 AM Anup Patel <anup@...infault.org> wrote:
>
> On Tue, Jul 21, 2020 at 6:41 AM Atish Patra <atishp@...shpatra.org> wrote:
> >
> > On Fri, Jul 17, 2020 at 12:52 AM Anup Patel <anup.patel@....com> wrote:
> > >
> > > We add a separate CLINT timer driver for Linux RISC-V M-mode (i.e.
> > > RISC-V NoMMU kernel).
> > >
> > > The CLINT MMIO device provides three things:
> > > 1. 64bit free running counter register
> > > 2. 64bit per-CPU time compare registers
> > > 3. 32bit per-CPU inter-processor interrupt registers
> > >
> > > Unlike other timer devices, CLINT provides IPI registers along with
> > > timer registers. To use CLINT IPI registers, the CLINT timer driver
> > > provides IPI related callbacks to arch/riscv.
> > >
> > > Signed-off-by: Anup Patel <anup.patel@....com>
> > > Tested-by: Emil Renner Berhing <kernel@...il.dk>
> > > ---
> > > drivers/clocksource/Kconfig | 9 ++
> > > drivers/clocksource/Makefile | 1 +
> > > drivers/clocksource/timer-clint.c | 231 ++++++++++++++++++++++++++++++
> > > include/linux/cpuhotplug.h | 1 +
> > > 4 files changed, 242 insertions(+)
> > > create mode 100644 drivers/clocksource/timer-clint.c
> > >
> > > diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> > > index 91418381fcd4..e1ce0d510a03 100644
> > > --- a/drivers/clocksource/Kconfig
> > > +++ b/drivers/clocksource/Kconfig
> > > @@ -658,6 +658,15 @@ 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
> > > + 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.
> > > +
> > > 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..e1698efa73a1
> > > --- /dev/null
> > > +++ b/drivers/clocksource/timer-clint.c
> > > @@ -0,0 +1,231 @@
> > > +// 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 notrace clint_get_cycles64(void)
> > > +{
> > > + return clint_get_cycles();
> > > +}
> > > +#else /* CONFIG_64BIT */
> > > +static u64 notrace 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 u64 clint_rdtime(struct clocksource *cs)
> > > +{
> > > + return clint_get_cycles64();
> > > +}
> > > +
> > > +static struct clocksource clint_clocksource = {
> > > + .name = "clint_clocksource",
> > > + .rating = 300,
> >
> > nit: Not aligned with other structure members.
> >
> > > + .mask = CLOCKSOURCE_MASK(64),
> > > + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> > > + .read = clint_rdtime,
> > > +};
> > > +
> > > +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,
> >
> > nit: Not aligned with other structure members.
>
> Okay, will update.
>
> > > +};
> > > +
> > > +static DEFINE_PER_CPU(bool, clint_clock_event_registered);
> > > +
> > > +static int clint_timer_starting_cpu(unsigned int cpu)
> > > +{
> > > + bool *registered = per_cpu_ptr(&clint_clock_event_registered, cpu);
> > > + struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
> > > +
> > > + if (!(*registered)) {
> > > + ce->cpumask = cpumask_of(cpu);
> > > + clockevents_config_and_register(ce, clint_timer_freq, 200,
> > > + ULONG_MAX);
> >
> > Is there a specific reason to choose different values from the timer-riscv ?
> > The min_delta is set to 100 and max_delta is set to 0x7fffffff in
> > timer-riscv driver.
>
> Not really, I will update. I think it's better to use 100 and ULONG_MAX to
> have fewer magic values.
>
Yeah. Looking at the other timer driver, max_delta is all over the place :).
I guess we should just keep the same max/min_delta between riscv timer
and clint driver.
> >
> > > + *registered = true;
> > > + }
> > > +
> > > + enable_percpu_irq(clint_timer_irq,
> > > + irq_get_trigger_type(clint_timer_irq));
> > > + 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_get_cycles64, 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;
> >
> > All the iounmap & return statements can be moved to a goto at the end
> > of the function.
>
> Okay, will update.
>
> >
> > > + }
> > > +
> > > + 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,
> > > --
> > > 2.25.1
> > >
> > >
> > > _______________________________________________
> > > linux-riscv mailing list
> > > linux-riscv@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
> >
> >
> >
> > --
> > Regards,
> > Atish
>
> Regards,
> Anup
--
Regards,
Atish
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