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Date: Mon, 1 Oct 2018 11:14:14 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Guo Ren <ren_guo@...ky.com>, tglx@...utronix.de,
jason@...edaemon.net, marc.zyngier@....com, robh+dt@...nel.org,
mark.rutland@....com, anurup.m@...wei.com,
Jonathan.Cameron@...wei.com, will.deacon@....com,
zhangshaokun@...ilicon.com, jhogan@...nel.org,
paul.burton@...s.com, peterz@...radead.org, f.fainelli@...il.com,
arnd@...db.de
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH V9 3/8] clocksource: add C-SKY SMP timer
On 01/10/2018 03:35, Guo Ren wrote:
> This timer is used by SMP system and use mfcr/mtcr instruction
> to access the regs.
>
> Changelog:
> - Remove #define CPUHP_AP_CSKY_TIMER_STARTING
> - Add CPUHP_AP_CSKY_TIMER_STARTING in cpuhotplug.h
> - Support csky mp timer alpha version.
> - Just use low-counter with 32bit width as clocksource.
> - Coding convention with upstream feed-back.
>
> Signed-off-by: Guo Ren <ren_guo@...ky.com>
> ---
> drivers/clocksource/Kconfig | 8 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/csky_mptimer.c | 176 +++++++++++++++++++++++++++++++++++++
> include/linux/cpuhotplug.h | 1 +
> 4 files changed, 186 insertions(+)
> create mode 100644 drivers/clocksource/csky_mptimer.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index a11f4ba..a28043f 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -620,4 +620,12 @@ config RISCV_TIMER
> is accessed via both the SBI and the rdcycle instruction. This is
> required for all RISC-V systems.
>
> +config CSKY_MPTIMER
> + bool "C-SKY Multi Processor Timer"
> + depends on CSKY
> + select TIMER_OF
> + help
> + Say yes here to enable C-SKY SMP timer driver used for C-SKY SMP
> + system.
> +
> endmenu
The same rule applies here for COMPILE_TEST.
And please rename the file: timer-mp-csky.c
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index db51b24..848c676 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -79,3 +79,4 @@ 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) += riscv_timer.o
> +obj-$(CONFIG_CSKY_MPTIMER) += csky_mptimer.o
> diff --git a/drivers/clocksource/csky_mptimer.c b/drivers/clocksource/csky_mptimer.c
> new file mode 100644
> index 0000000..9dc3cfb
> --- /dev/null
> +++ b/drivers/clocksource/csky_mptimer.c
> @@ -0,0 +1,176 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
> +
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/sched_clock.h>
> +#include <linux/cpu.h>
> +#include <asm/reg_ops.h>
> +
> +#include "timer-of.h"
> +
> +#define PTIM_CCVR "cr<3, 14>"
> +#define PTIM_CTLR "cr<0, 14>"
> +#define PTIM_LVR "cr<6, 14>"
> +#define PTIM_TSR "cr<1, 14>"
> +
> +static int csky_mptimer_set_next_event(unsigned long delta, struct clock_event_device *ce)
> +{
> + mtcr(PTIM_LVR, delta);
> +
> + return 0;
> +}
> +
> +static int csky_mptimer_shutdown(struct clock_event_device *ce)
> +{
> + mtcr(PTIM_CTLR, 0);
> +
> + return 0;
> +}
> +
> +static int csky_mptimer_oneshot(struct clock_event_device *ce)
> +{
> + mtcr(PTIM_CTLR, 1);
> +
> + return 0;
> +}
> +
> +static int csky_mptimer_oneshot_stopped(struct clock_event_device *ce)
> +{
> + mtcr(PTIM_CTLR, 0);
> +
> + return 0;
> +}
> +
> +static DEFINE_PER_CPU(struct timer_of, csky_to) = {
> + .flags = TIMER_OF_CLOCK,
> + .clkevt = {
> + .rating = 300,
> + .features = CLOCK_EVT_FEAT_PERCPU |
> + CLOCK_EVT_FEAT_ONESHOT,
> + .set_state_shutdown = csky_mptimer_shutdown,
> + .set_state_oneshot = csky_mptimer_oneshot,
> + .set_state_oneshot_stopped = csky_mptimer_oneshot_stopped,
> + .set_next_event = csky_mptimer_set_next_event,
> + },
> + .of_irq = {
> + .flags = IRQF_TIMER,
> + .percpu = 1,
> + },
See comment in the init function.
> +};
> +
> +static irqreturn_t timer_interrupt(int irq, void *dev)
> +{
> + struct timer_of *to = this_cpu_ptr(&csky_to);
> +
> + mtcr(PTIM_TSR, 0);
> +
> + to->clkevt.event_handler(&to->clkevt);
> +
> + return IRQ_HANDLED;
> +}
> +
> +/*
> + * clock event for percpu
> + */
> +static int csky_mptimer_starting_cpu(unsigned int cpu)
> +{
> + struct timer_of *to = per_cpu_ptr(&csky_to, cpu);
> +
> + to->clkevt.cpumask = cpumask_of(cpu);
> +
> + clockevents_config_and_register(&to->clkevt, timer_of_rate(to), 2, ULONG_MAX);
> +
> + enable_percpu_irq(timer_of_irq(to), 0);
> +
> + return 0;
> +}
> +
> +static int csky_mptimer_dying_cpu(unsigned int cpu)
> +{
> + struct timer_of *to = per_cpu_ptr(&csky_to, cpu);
> +
> + disable_percpu_irq(timer_of_irq(to));
> +
> + return 0;
> +}
> +
> +/*
> + * clock source
> + */
> +static u64 sched_clock_read(void)
> +{
> + return (u64) mfcr(PTIM_CCVR);
extra space
> +}
> +
> +static u64 clksrc_read(struct clocksource *c)
> +{
> + return (u64) mfcr(PTIM_CCVR);
extra space
> +}
> +
> +struct clocksource csky_clocksource = {
> + .name = "csky",
> + .rating = 400,
> + .mask = CLOCKSOURCE_MASK(32),
> + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> + .read = clksrc_read,
> +};
> +
> +static int __init csky_mptimer_init(struct device_node *np)
> +{
> + int ret, cpu;
> + struct timer_of *to;
> + int rate = 0;
> + int irq = 0;
> +
> + /*
> + * Csky_mptimer is designed for C-SKY SMP multi-processors and
> + * every core has it's own private irq and regs for clkevt and
> + * clksrc.
> + *
> + * The regs is accessed by cpu instruction: mfcr/mtcr instead of
> + * mmio map style. So we needn't mmio-address in dts, but we still
> + * need to give clk and irq number.
> + *
> + * We use private irq for the mptimer and irq number is the same
> + * for every core. So we use request_percpu_irq() in timer_of_init.
> + */
> +
extra line
> + for_each_possible_cpu(cpu) {
> + to = per_cpu_ptr(&csky_to, cpu);
> +
> + if (cpu == 0) {
> + to->flags |= TIMER_OF_IRQ;
> + to->of_irq.handler = timer_interrupt;
> +
> + ret = timer_of_init(np, to);
> + if (ret)
> + return ret;
> +
> + rate = timer_of_rate(to);
> + irq = to->of_irq.irq;
> + } else {
> + ret = timer_of_init(np, to);
> + if (ret)
> + return ret;
> +
> + to->of_clk.rate = rate;
> + to->of_irq.irq = irq;
> + }
> + }
Isn't possible to replace this loop which is a bit confusing by:
- no irq flag specified for timer-of
- request irq before
So we end up with:
irq = irq_of_parse_and_map(np, 0);
if (irq <= 0)
return -EINVAL;
ret = request_irq(irq, csky_timer_interrupt,
IRQF_TIMER | IRQF_PERCPU,
"csky_mp_timer", &csky_to));
if (ret)
return ret;
for_each_possible_cpu(cpu) {
to = per_cpu_ptr(&csky_to, cpu);
ret = timer_of_init(np, to);
if (ret)
goto rollback;
}
Alternatively, you can remove the timer_of struct and instantiate the
percpu stuff in cpuhp callbacks (cf. jcore_pit).
> + ret = cpuhp_setup_state(CPUHP_AP_CSKY_TIMER_STARTING,
> + "clockevents/csky/timer:starting",
> + csky_mptimer_starting_cpu,
> + csky_mptimer_dying_cpu);
> + if (ret) {
> + pr_err("%s: Failed to cpuhp_setup_state.\n", __func__);
> + return ret;
> + }
> +
> + clocksource_register_hz(&csky_clocksource, rate);
> + sched_clock_register(sched_clock_read, 32, rate);
> +
> + return 0;
> +}
> +TIMER_OF_DECLARE(csky_mptimer, "csky,mptimer", csky_mptimer_init);
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index caf40ad..e0cd2ba 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -126,6 +126,7 @@ enum cpuhp_state {
> CPUHP_AP_MIPS_GIC_TIMER_STARTING,
> CPUHP_AP_ARC_TIMER_STARTING,
> CPUHP_AP_RISCV_TIMER_STARTING,
> + CPUHP_AP_CSKY_TIMER_STARTING,
> CPUHP_AP_KVM_STARTING,
> CPUHP_AP_KVM_ARM_VGIC_INIT_STARTING,
> CPUHP_AP_KVM_ARM_VGIC_STARTING,
>
--
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