[v6,4/5] clocksource: add driver for i.MX EPIT timer

Message ID 20180607140544.22268-5-peron.clem@gmail.com
State New
Headers show
Series
  • Reintroduce i.MX EPIT Timer
Related show

Commit Message

Clément Péron June 7, 2018, 2:05 p.m.
From: Colin Didier <colin.didier@devialet.com>

Add driver for NXP's EPIT timer used in i.MX SoC.

Signed-off-by: Colin Didier <colin.didier@devialet.com>
Signed-off-by: Clément Peron <clement.peron@devialet.com>
---
 drivers/clocksource/Kconfig          |  11 ++
 drivers/clocksource/Makefile         |   1 +
 drivers/clocksource/timer-imx-epit.c | 265 +++++++++++++++++++++++++++
 3 files changed, 277 insertions(+)
 create mode 100644 drivers/clocksource/timer-imx-epit.c

Comments

Stefan Agner June 11, 2018, 12:31 p.m. | #1
On 07.06.2018 16:05, Clément Péron wrote:
> From: Colin Didier <colin.didier@devialet.com>
> 
> Add driver for NXP's EPIT timer used in i.MX SoC.
> 
> Signed-off-by: Colin Didier <colin.didier@devialet.com>
> Signed-off-by: Clément Peron <clement.peron@devialet.com>
> ---
>  drivers/clocksource/Kconfig          |  11 ++
>  drivers/clocksource/Makefile         |   1 +
>  drivers/clocksource/timer-imx-epit.c | 265 +++++++++++++++++++++++++++
>  3 files changed, 277 insertions(+)
>  create mode 100644 drivers/clocksource/timer-imx-epit.c
> 
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 8e8a09755d10..790478afd02c 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -576,6 +576,17 @@ config H8300_TPU
>  	  This enables the clocksource for the H8300 platform with the
>  	  H8S2678 cpu.
>  
> +config CLKSRC_IMX_EPIT
> +	bool "Clocksource using i.MX EPIT"
> +	depends on CLKDEV_LOOKUP && (ARCH_MXC || COMPILE_TEST)
> +	select CLKSRC_MMIO
> +	help
> +	  This enables EPIT support available on some i.MX platforms.
> +	  Normally you don't have a reason to do so as the EPIT has
> +	  the same features and uses the same clocks as the GPT.
> +	  Anyway, on some systems the GPT may be in use for other
> +	  purposes.
> +
>  config CLKSRC_IMX_GPT
>  	bool "Clocksource using i.MX GPT" if COMPILE_TEST
>  	depends on ARM && CLKDEV_LOOKUP
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 00caf37e52f9..d9426f69ec69 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -69,6 +69,7 @@ obj-$(CONFIG_INTEGRATOR_AP_TIMER)	+= timer-integrator-ap.o
>  obj-$(CONFIG_CLKSRC_VERSATILE)		+= versatile.o
>  obj-$(CONFIG_CLKSRC_MIPS_GIC)		+= mips-gic-timer.o
>  obj-$(CONFIG_CLKSRC_TANGO_XTAL)		+= tango_xtal.o
> +obj-$(CONFIG_CLKSRC_IMX_EPIT)		+= timer-imx-epit.o
>  obj-$(CONFIG_CLKSRC_IMX_GPT)		+= timer-imx-gpt.o
>  obj-$(CONFIG_CLKSRC_IMX_TPM)		+= timer-imx-tpm.o
>  obj-$(CONFIG_ASM9260_TIMER)		+= asm9260_timer.o
> diff --git a/drivers/clocksource/timer-imx-epit.c
> b/drivers/clocksource/timer-imx-epit.c
> new file mode 100644
> index 000000000000..15f70e210fad
> --- /dev/null
> +++ b/drivers/clocksource/timer-imx-epit.c
> @@ -0,0 +1,265 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * i.MX EPIT Timer
> + *
> + * Copyright (C) 2010 Sascha Hauer <s.hauer@pengutronix.de>
> + * Copyright (C) 2018 Colin Didier <colin.didier@devialet.com>
> + * Copyright (C) 2018 Clément Péron <clement.peron@devialet.com>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clockchips.h>
> +#include <linux/interrupt.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/sched_clock.h>
> +#include <linux/slab.h>
> +
> +#define EPITCR				0x00
> +#define EPITSR				0x04
> +#define EPITLR				0x08
> +#define EPITCMPR			0x0c
> +#define EPITCNR				0x10
> +
> +#define EPITCR_EN			BIT(0)
> +#define EPITCR_ENMOD			BIT(1)
> +#define EPITCR_OCIEN			BIT(2)
> +#define EPITCR_RLD			BIT(3)
> +#define EPITCR_PRESC(x)			(((x) & 0xfff) << 4)
> +#define EPITCR_SWR			BIT(16)
> +#define EPITCR_IOVW			BIT(17)
> +#define EPITCR_DBGEN			BIT(18)
> +#define EPITCR_WAITEN			BIT(19)
> +#define EPITCR_RES			BIT(20)
> +#define EPITCR_STOPEN			BIT(21)
> +#define EPITCR_OM_DISCON		(0 << 22)
> +#define EPITCR_OM_TOGGLE		(1 << 22)
> +#define EPITCR_OM_CLEAR			(2 << 22)
> +#define EPITCR_OM_SET			(3 << 22)
> +#define EPITCR_CLKSRC_OFF		(0 << 24)
> +#define EPITCR_CLKSRC_PERIPHERAL	(1 << 24)
> +#define EPITCR_CLKSRC_REF_HIGH		(2 << 24)
> +#define EPITCR_CLKSRC_REF_LOW		(3 << 24)
> +
> +#define EPITSR_OCIF			BIT(0)
> +
> +struct epit_timer {
> +	void __iomem *base;
> +	int irq;
> +	struct clk *clk;
> +	struct clock_event_device ced;
> +	struct irqaction act;
> +};
> +
> +static void __iomem *sched_clock_reg;
> +
> +static inline struct epit_timer *to_epit_timer(struct clock_event_device *ced)
> +{
> +	return container_of(ced, struct epit_timer, ced);
> +}
> +
> +static inline void epit_irq_disable(struct epit_timer *epittm)
> +{
> +	u32 val;
> +
> +	val = readl_relaxed(epittm->base + EPITCR);
> +	writel_relaxed(val & ~EPITCR_OCIEN, epittm->base + EPITCR);
> +}
> +
> +static inline void epit_irq_enable(struct epit_timer *epittm)
> +{
> +	u32 val;
> +
> +	val = readl_relaxed(epittm->base + EPITCR);
> +	writel_relaxed(val | EPITCR_OCIEN, epittm->base + EPITCR);
> +}
> +
> +static void epit_irq_acknowledge(struct epit_timer *epittm)
> +{
> +	writel_relaxed(EPITSR_OCIF, epittm->base + EPITSR);
> +}
> +
> +static u64 notrace epit_read_sched_clock(void)
> +{
> +	return ~readl_relaxed(sched_clock_reg);
> +}
> +
> +static int epit_set_next_event(unsigned long cycles,
> +			       struct clock_event_device *ced)
> +{
> +	struct epit_timer *epittm = to_epit_timer(ced);
> +	unsigned long tcmp;
> +
> +	tcmp = readl_relaxed(epittm->base + EPITCNR) - cycles;
> +	writel_relaxed(tcmp, epittm->base + EPITCMPR);
> +
> +	return 0;
> +}
> +
> +/* Left event sources disabled, no more interrupts appear */
> +static int epit_shutdown(struct clock_event_device *ced)
> +{
> +	struct epit_timer *epittm = to_epit_timer(ced);
> +	unsigned long flags;
> +
> +	/*
> +	 * The timer interrupt generation is disabled at least
> +	 * for enough time to call epit_set_next_event()
> +	 */
> +	local_irq_save(flags);
> +
> +	/* Disable interrupt in EPIT module */
> +	epit_irq_disable(epittm);
> +
> +	/* Clear pending interrupt */
> +	epit_irq_acknowledge(epittm);
> +
> +	local_irq_restore(flags);
> +
> +	return 0;
> +}
> +
> +static int epit_set_oneshot(struct clock_event_device *ced)
> +{
> +	struct epit_timer *epittm = to_epit_timer(ced);
> +	unsigned long flags;
> +
> +	/*
> +	 * The timer interrupt generation is disabled at least
> +	 * for enough time to call epit_set_next_event()
> +	 */
> +	local_irq_save(flags);
> +
> +	/* Disable interrupt in EPIT module */
> +	epit_irq_disable(epittm);
> +
> +	/* Clear pending interrupt, only while switching mode */
> +	if (!clockevent_state_oneshot(ced))
> +		epit_irq_acknowledge(epittm);
> +
> +	/*
> +	 * Do not put overhead of interrupt enable/disable into
> +	 * epit_set_next_event(), the core has about 4 minutes
> +	 * to call epit_set_next_event() or shutdown clock after
> +	 * mode switching
> +	 */
> +	epit_irq_enable(epittm);
> +	local_irq_restore(flags);
> +
> +	return 0;
> +}
> +
> +static irqreturn_t epit_timer_interrupt(int irq, void *dev_id)
> +{
> +	struct clock_event_device *ced = dev_id;
> +	struct epit_timer *epittm = to_epit_timer(ced);
> +
> +	epit_irq_acknowledge(epittm);
> +
> +	ced->event_handler(ced);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int __init epit_clocksource_init(struct epit_timer *epittm)
> +{
> +	unsigned int c = clk_get_rate(epittm->clk);
> +
> +	sched_clock_reg = epittm->base + EPITCNR;
> +	sched_clock_register(epit_read_sched_clock, 32, c);
> +
> +	return clocksource_mmio_init(epittm->base + EPITCNR, "epit", c, 200, 32,
> +				     clocksource_mmio_readl_down);
> +}
> +
> +static int __init epit_clockevent_init(struct epit_timer *epittm)
> +{
> +	struct clock_event_device *ced = &epittm->ced;
> +	struct irqaction *act = &epittm->act;
> +
> +	ced->name = "epit";
> +	ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ;
> +	ced->set_state_shutdown = epit_shutdown;
> +	ced->tick_resume = epit_shutdown;
> +	ced->set_state_oneshot = epit_set_oneshot;
> +	ced->set_next_event = epit_set_next_event;
> +	ced->rating = 200;
> +	ced->cpumask = cpumask_of(0);
> +	ced->irq = epittm->irq;
> +	clockevents_config_and_register(ced, clk_get_rate(epittm->clk),
> +					0xff, 0xfffffffe);
> +
> +	act->name = "i.MX EPIT Timer Tick",
> +	act->flags = IRQF_TIMER | IRQF_IRQPOLL;
> +	act->handler = epit_timer_interrupt;
> +	act->dev_id = ced;
> +
> +	/* Make irqs happen */
> +	return setup_irq(epittm->irq, act);
> +}
> +
> +static int __init epit_timer_init(struct device_node *np)
> +{
> +	struct epit_timer *epittm;
> +	int ret;
> +
> +	epittm = kzalloc(sizeof(*epittm), GFP_KERNEL);
> +	if (!epittm)
> +		return -ENOMEM;
> +
> +	epittm->base = of_iomap(np, 0);
> +	if (!epittm->base) {
> +		ret = -ENXIO;
> +		goto out_kfree;
> +	}
> +
> +	epittm->irq = irq_of_parse_and_map(np, 0);
> +	if (!epittm->irq) {
> +		ret = -EINVAL;
> +		goto out_iounmap;
> +	}
> +
> +        /* Get EPIT clock */
> +        epittm->clk = of_clk_get(np, 0);
> +        if (IS_ERR(epittm->clk)) {
> +		pr_err("i.MX EPIT: unable to get clk\n");
> +		ret = PTR_ERR(epittm->clk);
> +		goto out_iounmap;
> +        }

There is something off with indent here.

There is a helper library in drivers/clocksource/timer-of.c which might
be useful for this driver.

--
Stefan

> +
> +	ret = clk_prepare_enable(epittm->clk);
> +	if (ret) {
> +		pr_err("i.MX EPIT: unable to prepare+enable clk\n");
> +		goto out_iounmap;
> +	}
> +
> +	/* Initialise to a known state (all timers off, and timing reset) */
> +	writel_relaxed(0x0, epittm->base + EPITCR);
> +	writel_relaxed(0xffffffff, epittm->base + EPITLR);
> +	writel_relaxed(EPITCR_EN | EPITCR_CLKSRC_REF_HIGH | EPITCR_WAITEN,
> +		       epittm->base + EPITCR);
> +
> +	ret = epit_clocksource_init(epittm);
> +	if (ret) {
> +		pr_err("i.MX EPIT: failed to init clocksource\n");
> +		goto out_clk_disable;
> +	}
> +
> +	ret = epit_clockevent_init(epittm);
> +	if (ret) {
> +		pr_err("i.MX EPIT: failed to init clockevent\n");
> +		goto out_clk_disable;
> +	}
> +
> +	return 0;
> +
> +out_clk_disable:
> +	clk_disable_unprepare(epittm->clk);
> +out_iounmap:
> +	iounmap(epittm->base);
> +out_kfree:
> +	kfree(epittm);
> +
> +	return ret;
> +}
> +TIMER_OF_DECLARE(epit_timer, "fsl,imx31-epit", epit_timer_init);
Clément Péron June 11, 2018, 12:42 p.m. | #2
Hi Stefan,


> > +
> > +#define EPITCR                               0x00
> > +#define EPITSR                               0x04
> > +#define EPITLR                               0x08
> > +#define EPITCMPR                     0x0c
> > +#define EPITCNR                              0x10
> > +
> > +#define EPITCR_EN                    BIT(0)
> > +#define EPITCR_ENMOD                 BIT(1)
> > +#define EPITCR_OCIEN                 BIT(2)
> > +#define EPITCR_RLD                   BIT(3)
> > +#define EPITCR_PRESC(x)                      (((x) & 0xfff) << 4)
> > +#define EPITCR_SWR                   BIT(16)
> > +#define EPITCR_IOVW                  BIT(17)
> > +#define EPITCR_DBGEN                 BIT(18)
> > +#define EPITCR_WAITEN                        BIT(19)
> > +#define EPITCR_RES                   BIT(20)
> > +#define EPITCR_STOPEN                        BIT(21)
> > +#define EPITCR_OM_DISCON             (0 << 22)
> > +#define EPITCR_OM_TOGGLE             (1 << 22)
> > +#define EPITCR_OM_CLEAR                      (2 << 22)
> > +#define EPITCR_OM_SET                        (3 << 22)
> > +#define EPITCR_CLKSRC_OFF            (0 << 24)
> > +#define EPITCR_CLKSRC_PERIPHERAL     (1 << 24)
> > +#define EPITCR_CLKSRC_REF_HIGH               (2 << 24)
> > +#define EPITCR_CLKSRC_REF_LOW                (3 << 24)
> > +
> > +#define EPITSR_OCIF                  BIT(0)
> > +
> > +struct epit_timer {
> > +     void __iomem *base;
> > +     int irq;
> > +     struct clk *clk;
> > +     struct clock_event_device ced;
> > +     struct irqaction act;
> > +};
> > +
> > +static void __iomem *sched_clock_reg;
> > +
> > +static inline struct epit_timer *to_epit_timer(struct clock_event_device *ced)
> > +{
> > +     return container_of(ced, struct epit_timer, ced);
> > +}
> > +
> > +static inline void epit_irq_disable(struct epit_timer *epittm)
> > +{
> > +     u32 val;
> > +
> > +     val = readl_relaxed(epittm->base + EPITCR);
> > +     writel_relaxed(val & ~EPITCR_OCIEN, epittm->base + EPITCR);
> > +}
> > +
> > +static inline void epit_irq_enable(struct epit_timer *epittm)
> > +{
> > +     u32 val;
> > +
> > +     val = readl_relaxed(epittm->base + EPITCR);
> > +     writel_relaxed(val | EPITCR_OCIEN, epittm->base + EPITCR);
> > +}
> > +
> > +static void epit_irq_acknowledge(struct epit_timer *epittm)
> > +{
> > +     writel_relaxed(EPITSR_OCIF, epittm->base + EPITSR);
> > +}
> > +
> > +static u64 notrace epit_read_sched_clock(void)
> > +{
> > +     return ~readl_relaxed(sched_clock_reg);
> > +}
> > +
> > +static int epit_set_next_event(unsigned long cycles,
> > +                            struct clock_event_device *ced)
> > +{
> > +     struct epit_timer *epittm = to_epit_timer(ced);
> > +     unsigned long tcmp;
> > +
> > +     tcmp = readl_relaxed(epittm->base + EPITCNR) - cycles;
> > +     writel_relaxed(tcmp, epittm->base + EPITCMPR);
> > +
> > +     return 0;
> > +}
> > +
> > +/* Left event sources disabled, no more interrupts appear */
> > +static int epit_shutdown(struct clock_event_device *ced)
> > +{
> > +     struct epit_timer *epittm = to_epit_timer(ced);
> > +     unsigned long flags;
> > +
> > +     /*
> > +      * The timer interrupt generation is disabled at least
> > +      * for enough time to call epit_set_next_event()
> > +      */
> > +     local_irq_save(flags);
> > +
> > +     /* Disable interrupt in EPIT module */
> > +     epit_irq_disable(epittm);
> > +
> > +     /* Clear pending interrupt */
> > +     epit_irq_acknowledge(epittm);
> > +
> > +     local_irq_restore(flags);
> > +
> > +     return 0;
> > +}
> > +
> > +static int epit_set_oneshot(struct clock_event_device *ced)
> > +{
> > +     struct epit_timer *epittm = to_epit_timer(ced);
> > +     unsigned long flags;
> > +
> > +     /*
> > +      * The timer interrupt generation is disabled at least
> > +      * for enough time to call epit_set_next_event()
> > +      */
> > +     local_irq_save(flags);
> > +
> > +     /* Disable interrupt in EPIT module */
> > +     epit_irq_disable(epittm);
> > +
> > +     /* Clear pending interrupt, only while switching mode */
> > +     if (!clockevent_state_oneshot(ced))
> > +             epit_irq_acknowledge(epittm);
> > +
> > +     /*
> > +      * Do not put overhead of interrupt enable/disable into
> > +      * epit_set_next_event(), the core has about 4 minutes
> > +      * to call epit_set_next_event() or shutdown clock after
> > +      * mode switching
> > +      */
> > +     epit_irq_enable(epittm);
> > +     local_irq_restore(flags);
> > +
> > +     return 0;
> > +}
> > +
> > +static irqreturn_t epit_timer_interrupt(int irq, void *dev_id)
> > +{
> > +     struct clock_event_device *ced = dev_id;
> > +     struct epit_timer *epittm = to_epit_timer(ced);
> > +
> > +     epit_irq_acknowledge(epittm);
> > +
> > +     ced->event_handler(ced);
> > +
> > +     return IRQ_HANDLED;
> > +}
> > +
> > +static int __init epit_clocksource_init(struct epit_timer *epittm)
> > +{
> > +     unsigned int c = clk_get_rate(epittm->clk);
> > +
> > +     sched_clock_reg = epittm->base + EPITCNR;
> > +     sched_clock_register(epit_read_sched_clock, 32, c);
> > +
> > +     return clocksource_mmio_init(epittm->base + EPITCNR, "epit", c, 200, 32,
> > +                                  clocksource_mmio_readl_down);
> > +}
> > +
> > +static int __init epit_clockevent_init(struct epit_timer *epittm)
> > +{
> > +     struct clock_event_device *ced = &epittm->ced;
> > +     struct irqaction *act = &epittm->act;
> > +
> > +     ced->name = "epit";
> > +     ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ;
> > +     ced->set_state_shutdown = epit_shutdown;
> > +     ced->tick_resume = epit_shutdown;
> > +     ced->set_state_oneshot = epit_set_oneshot;
> > +     ced->set_next_event = epit_set_next_event;
> > +     ced->rating = 200;
> > +     ced->cpumask = cpumask_of(0);
> > +     ced->irq = epittm->irq;
> > +     clockevents_config_and_register(ced, clk_get_rate(epittm->clk),
> > +                                     0xff, 0xfffffffe);
> > +
> > +     act->name = "i.MX EPIT Timer Tick",
> > +     act->flags = IRQF_TIMER | IRQF_IRQPOLL;
> > +     act->handler = epit_timer_interrupt;
> > +     act->dev_id = ced;
> > +
> > +     /* Make irqs happen */
> > +     return setup_irq(epittm->irq, act);
> > +}
> > +
> > +static int __init epit_timer_init(struct device_node *np)
> > +{
> > +     struct epit_timer *epittm;
> > +     int ret;
> > +
> > +     epittm = kzalloc(sizeof(*epittm), GFP_KERNEL);
> > +     if (!epittm)
> > +             return -ENOMEM;
> > +
> > +     epittm->base = of_iomap(np, 0);
> > +     if (!epittm->base) {
> > +             ret = -ENXIO;
> > +             goto out_kfree;
> > +     }
> > +
> > +     epittm->irq = irq_of_parse_and_map(np, 0);
> > +     if (!epittm->irq) {
> > +             ret = -EINVAL;
> > +             goto out_iounmap;
> > +     }
> > +
> > +        /* Get EPIT clock */
> > +        epittm->clk = of_clk_get(np, 0);
> > +        if (IS_ERR(epittm->clk)) {
> > +             pr_err("i.MX EPIT: unable to get clk\n");
> > +             ret = PTR_ERR(epittm->clk);
> > +             goto out_iounmap;
> > +        }
>
> There is something off with indent here.
Thanks for pointing out that, I will fix it.

>
> There is a helper library in drivers/clocksource/timer-of.c which might
> be useful for this driver.
Indeed, but will require a bit of rewrite.

Clement

>
> --
> Stefan
>
> > +
> > +     ret = clk_prepare_enable(epittm->clk);
> > +     if (ret) {
> > +             pr_err("i.MX EPIT: unable to prepare+enable clk\n");
> > +             goto out_iounmap;
> > +     }
> > +
> > +     /* Initialise to a known state (all timers off, and timing reset) */
> > +     writel_relaxed(0x0, epittm->base + EPITCR);
> > +     writel_relaxed(0xffffffff, epittm->base + EPITLR);
> > +     writel_relaxed(EPITCR_EN | EPITCR_CLKSRC_REF_HIGH | EPITCR_WAITEN,
> > +                    epittm->base + EPITCR);
> > +
> > +     ret = epit_clocksource_init(epittm);
> > +     if (ret) {
> > +             pr_err("i.MX EPIT: failed to init clocksource\n");
> > +             goto out_clk_disable;
> > +     }
> > +
> > +     ret = epit_clockevent_init(epittm);
> > +     if (ret) {
> > +             pr_err("i.MX EPIT: failed to init clockevent\n");
> > +             goto out_clk_disable;
> > +     }
> > +
> > +     return 0;
> > +
> > +out_clk_disable:
> > +     clk_disable_unprepare(epittm->clk);
> > +out_iounmap:
> > +     iounmap(epittm->base);
> > +out_kfree:
> > +     kfree(epittm);
> > +
> > +     return ret;
> > +}
> > +TIMER_OF_DECLARE(epit_timer, "fsl,imx31-epit", epit_timer_init);
Stefan Agner June 11, 2018, 12:46 p.m. | #3
On 11.06.2018 14:42, Clément Péron wrote:
> Hi Stefan,
> 
> 
>> > +
>> > +#define EPITCR                               0x00
>> > +#define EPITSR                               0x04
>> > +#define EPITLR                               0x08
>> > +#define EPITCMPR                     0x0c
>> > +#define EPITCNR                              0x10
>> > +
>> > +#define EPITCR_EN                    BIT(0)
>> > +#define EPITCR_ENMOD                 BIT(1)
>> > +#define EPITCR_OCIEN                 BIT(2)
>> > +#define EPITCR_RLD                   BIT(3)
>> > +#define EPITCR_PRESC(x)                      (((x) & 0xfff) << 4)
>> > +#define EPITCR_SWR                   BIT(16)
>> > +#define EPITCR_IOVW                  BIT(17)
>> > +#define EPITCR_DBGEN                 BIT(18)
>> > +#define EPITCR_WAITEN                        BIT(19)
>> > +#define EPITCR_RES                   BIT(20)
>> > +#define EPITCR_STOPEN                        BIT(21)
>> > +#define EPITCR_OM_DISCON             (0 << 22)
>> > +#define EPITCR_OM_TOGGLE             (1 << 22)
>> > +#define EPITCR_OM_CLEAR                      (2 << 22)
>> > +#define EPITCR_OM_SET                        (3 << 22)
>> > +#define EPITCR_CLKSRC_OFF            (0 << 24)
>> > +#define EPITCR_CLKSRC_PERIPHERAL     (1 << 24)
>> > +#define EPITCR_CLKSRC_REF_HIGH               (2 << 24)
>> > +#define EPITCR_CLKSRC_REF_LOW                (3 << 24)
>> > +
>> > +#define EPITSR_OCIF                  BIT(0)
>> > +
>> > +struct epit_timer {
>> > +     void __iomem *base;
>> > +     int irq;
>> > +     struct clk *clk;
>> > +     struct clock_event_device ced;
>> > +     struct irqaction act;
>> > +};
>> > +
>> > +static void __iomem *sched_clock_reg;
>> > +
>> > +static inline struct epit_timer *to_epit_timer(struct clock_event_device *ced)
>> > +{
>> > +     return container_of(ced, struct epit_timer, ced);
>> > +}
>> > +
>> > +static inline void epit_irq_disable(struct epit_timer *epittm)
>> > +{
>> > +     u32 val;
>> > +
>> > +     val = readl_relaxed(epittm->base + EPITCR);
>> > +     writel_relaxed(val & ~EPITCR_OCIEN, epittm->base + EPITCR);
>> > +}
>> > +
>> > +static inline void epit_irq_enable(struct epit_timer *epittm)
>> > +{
>> > +     u32 val;
>> > +
>> > +     val = readl_relaxed(epittm->base + EPITCR);
>> > +     writel_relaxed(val | EPITCR_OCIEN, epittm->base + EPITCR);
>> > +}
>> > +
>> > +static void epit_irq_acknowledge(struct epit_timer *epittm)
>> > +{
>> > +     writel_relaxed(EPITSR_OCIF, epittm->base + EPITSR);
>> > +}
>> > +
>> > +static u64 notrace epit_read_sched_clock(void)
>> > +{
>> > +     return ~readl_relaxed(sched_clock_reg);
>> > +}
>> > +
>> > +static int epit_set_next_event(unsigned long cycles,
>> > +                            struct clock_event_device *ced)
>> > +{
>> > +     struct epit_timer *epittm = to_epit_timer(ced);
>> > +     unsigned long tcmp;
>> > +
>> > +     tcmp = readl_relaxed(epittm->base + EPITCNR) - cycles;
>> > +     writel_relaxed(tcmp, epittm->base + EPITCMPR);
>> > +
>> > +     return 0;
>> > +}
>> > +
>> > +/* Left event sources disabled, no more interrupts appear */
>> > +static int epit_shutdown(struct clock_event_device *ced)
>> > +{
>> > +     struct epit_timer *epittm = to_epit_timer(ced);
>> > +     unsigned long flags;
>> > +
>> > +     /*
>> > +      * The timer interrupt generation is disabled at least
>> > +      * for enough time to call epit_set_next_event()
>> > +      */
>> > +     local_irq_save(flags);
>> > +
>> > +     /* Disable interrupt in EPIT module */
>> > +     epit_irq_disable(epittm);
>> > +
>> > +     /* Clear pending interrupt */
>> > +     epit_irq_acknowledge(epittm);
>> > +
>> > +     local_irq_restore(flags);
>> > +
>> > +     return 0;
>> > +}
>> > +
>> > +static int epit_set_oneshot(struct clock_event_device *ced)
>> > +{
>> > +     struct epit_timer *epittm = to_epit_timer(ced);
>> > +     unsigned long flags;
>> > +
>> > +     /*
>> > +      * The timer interrupt generation is disabled at least
>> > +      * for enough time to call epit_set_next_event()
>> > +      */
>> > +     local_irq_save(flags);
>> > +
>> > +     /* Disable interrupt in EPIT module */
>> > +     epit_irq_disable(epittm);
>> > +
>> > +     /* Clear pending interrupt, only while switching mode */
>> > +     if (!clockevent_state_oneshot(ced))
>> > +             epit_irq_acknowledge(epittm);
>> > +
>> > +     /*
>> > +      * Do not put overhead of interrupt enable/disable into
>> > +      * epit_set_next_event(), the core has about 4 minutes
>> > +      * to call epit_set_next_event() or shutdown clock after
>> > +      * mode switching
>> > +      */
>> > +     epit_irq_enable(epittm);
>> > +     local_irq_restore(flags);
>> > +
>> > +     return 0;
>> > +}
>> > +
>> > +static irqreturn_t epit_timer_interrupt(int irq, void *dev_id)
>> > +{
>> > +     struct clock_event_device *ced = dev_id;
>> > +     struct epit_timer *epittm = to_epit_timer(ced);
>> > +
>> > +     epit_irq_acknowledge(epittm);
>> > +
>> > +     ced->event_handler(ced);
>> > +
>> > +     return IRQ_HANDLED;
>> > +}
>> > +
>> > +static int __init epit_clocksource_init(struct epit_timer *epittm)
>> > +{
>> > +     unsigned int c = clk_get_rate(epittm->clk);
>> > +
>> > +     sched_clock_reg = epittm->base + EPITCNR;
>> > +     sched_clock_register(epit_read_sched_clock, 32, c);
>> > +
>> > +     return clocksource_mmio_init(epittm->base + EPITCNR, "epit", c, 200, 32,
>> > +                                  clocksource_mmio_readl_down);
>> > +}
>> > +
>> > +static int __init epit_clockevent_init(struct epit_timer *epittm)
>> > +{
>> > +     struct clock_event_device *ced = &epittm->ced;
>> > +     struct irqaction *act = &epittm->act;
>> > +
>> > +     ced->name = "epit";
>> > +     ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ;
>> > +     ced->set_state_shutdown = epit_shutdown;
>> > +     ced->tick_resume = epit_shutdown;
>> > +     ced->set_state_oneshot = epit_set_oneshot;
>> > +     ced->set_next_event = epit_set_next_event;
>> > +     ced->rating = 200;
>> > +     ced->cpumask = cpumask_of(0);
>> > +     ced->irq = epittm->irq;
>> > +     clockevents_config_and_register(ced, clk_get_rate(epittm->clk),
>> > +                                     0xff, 0xfffffffe);
>> > +
>> > +     act->name = "i.MX EPIT Timer Tick",
>> > +     act->flags = IRQF_TIMER | IRQF_IRQPOLL;
>> > +     act->handler = epit_timer_interrupt;
>> > +     act->dev_id = ced;
>> > +
>> > +     /* Make irqs happen */
>> > +     return setup_irq(epittm->irq, act);
>> > +}
>> > +
>> > +static int __init epit_timer_init(struct device_node *np)
>> > +{
>> > +     struct epit_timer *epittm;
>> > +     int ret;
>> > +
>> > +     epittm = kzalloc(sizeof(*epittm), GFP_KERNEL);
>> > +     if (!epittm)
>> > +             return -ENOMEM;
>> > +
>> > +     epittm->base = of_iomap(np, 0);
>> > +     if (!epittm->base) {
>> > +             ret = -ENXIO;
>> > +             goto out_kfree;
>> > +     }
>> > +
>> > +     epittm->irq = irq_of_parse_and_map(np, 0);
>> > +     if (!epittm->irq) {
>> > +             ret = -EINVAL;
>> > +             goto out_iounmap;
>> > +     }
>> > +
>> > +        /* Get EPIT clock */
>> > +        epittm->clk = of_clk_get(np, 0);
>> > +        if (IS_ERR(epittm->clk)) {
>> > +             pr_err("i.MX EPIT: unable to get clk\n");
>> > +             ret = PTR_ERR(epittm->clk);
>> > +             goto out_iounmap;
>> > +        }
>>
>> There is something off with indent here.
> Thanks for pointing out that, I will fix it.
> 
>>
>> There is a helper library in drivers/clocksource/timer-of.c which might
>> be useful for this driver.
> Indeed, but will require a bit of rewrite.

That is fine for me ;-) Afaict, if should be simplify code a quite a
bit, and doable with reasonable amount of work.

It is typically the expectation for new drivers to make use of such
libraries. In the end it is up to the clocksource maintainer(s) to
decide whether they make it as an requirement for this driver.

--
Stefan

> 
> Clement
> 
>>
>> --
>> Stefan
>>
>> > +
>> > +     ret = clk_prepare_enable(epittm->clk);
>> > +     if (ret) {
>> > +             pr_err("i.MX EPIT: unable to prepare+enable clk\n");
>> > +             goto out_iounmap;
>> > +     }
>> > +
>> > +     /* Initialise to a known state (all timers off, and timing reset) */
>> > +     writel_relaxed(0x0, epittm->base + EPITCR);
>> > +     writel_relaxed(0xffffffff, epittm->base + EPITLR);
>> > +     writel_relaxed(EPITCR_EN | EPITCR_CLKSRC_REF_HIGH | EPITCR_WAITEN,
>> > +                    epittm->base + EPITCR);
>> > +
>> > +     ret = epit_clocksource_init(epittm);
>> > +     if (ret) {
>> > +             pr_err("i.MX EPIT: failed to init clocksource\n");
>> > +             goto out_clk_disable;
>> > +     }
>> > +
>> > +     ret = epit_clockevent_init(epittm);
>> > +     if (ret) {
>> > +             pr_err("i.MX EPIT: failed to init clockevent\n");
>> > +             goto out_clk_disable;
>> > +     }
>> > +
>> > +     return 0;
>> > +
>> > +out_clk_disable:
>> > +     clk_disable_unprepare(epittm->clk);
>> > +out_iounmap:
>> > +     iounmap(epittm->base);
>> > +out_kfree:
>> > +     kfree(epittm);
>> > +
>> > +     return ret;
>> > +}
>> > +TIMER_OF_DECLARE(epit_timer, "fsl,imx31-epit", epit_timer_init);
Vladimir Zapolskiy June 11, 2018, 2:40 p.m. | #4
On 06/07/2018 05:05 PM, Clément Péron wrote:
> From: Colin Didier <colin.didier@devialet.com>
> 
> Add driver for NXP's EPIT timer used in i.MX SoC.
> 
> Signed-off-by: Colin Didier <colin.didier@devialet.com>
> Signed-off-by: Clément Peron <clement.peron@devialet.com>

Reviewed-by: Vladimir Zapolskiy <vz@mleia.com>
Tested-by: Vladimir Zapolskiy <vz@mleia.com>

I tested the driver on i.MX31 only, and I didn't find any problems.

Please fix the indentation issue found by Stefan in v7.

Regarding utilization of timer-of.c it can be postponed IMHO,
but it's up to clocksource maintainers and you to decide, and if
you do such an update for v7, then please don't add my tags,
I'll review and test it again.

--
With best wishes,
Vladimir

Patch

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 8e8a09755d10..790478afd02c 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -576,6 +576,17 @@  config H8300_TPU
 	  This enables the clocksource for the H8300 platform with the
 	  H8S2678 cpu.
 
+config CLKSRC_IMX_EPIT
+	bool "Clocksource using i.MX EPIT"
+	depends on CLKDEV_LOOKUP && (ARCH_MXC || COMPILE_TEST)
+	select CLKSRC_MMIO
+	help
+	  This enables EPIT support available on some i.MX platforms.
+	  Normally you don't have a reason to do so as the EPIT has
+	  the same features and uses the same clocks as the GPT.
+	  Anyway, on some systems the GPT may be in use for other
+	  purposes.
+
 config CLKSRC_IMX_GPT
 	bool "Clocksource using i.MX GPT" if COMPILE_TEST
 	depends on ARM && CLKDEV_LOOKUP
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 00caf37e52f9..d9426f69ec69 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -69,6 +69,7 @@  obj-$(CONFIG_INTEGRATOR_AP_TIMER)	+= timer-integrator-ap.o
 obj-$(CONFIG_CLKSRC_VERSATILE)		+= versatile.o
 obj-$(CONFIG_CLKSRC_MIPS_GIC)		+= mips-gic-timer.o
 obj-$(CONFIG_CLKSRC_TANGO_XTAL)		+= tango_xtal.o
+obj-$(CONFIG_CLKSRC_IMX_EPIT)		+= timer-imx-epit.o
 obj-$(CONFIG_CLKSRC_IMX_GPT)		+= timer-imx-gpt.o
 obj-$(CONFIG_CLKSRC_IMX_TPM)		+= timer-imx-tpm.o
 obj-$(CONFIG_ASM9260_TIMER)		+= asm9260_timer.o
diff --git a/drivers/clocksource/timer-imx-epit.c b/drivers/clocksource/timer-imx-epit.c
new file mode 100644
index 000000000000..15f70e210fad
--- /dev/null
+++ b/drivers/clocksource/timer-imx-epit.c
@@ -0,0 +1,265 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * i.MX EPIT Timer
+ *
+ * Copyright (C) 2010 Sascha Hauer <s.hauer@pengutronix.de>
+ * Copyright (C) 2018 Colin Didier <colin.didier@devialet.com>
+ * Copyright (C) 2018 Clément Péron <clement.peron@devialet.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/sched_clock.h>
+#include <linux/slab.h>
+
+#define EPITCR				0x00
+#define EPITSR				0x04
+#define EPITLR				0x08
+#define EPITCMPR			0x0c
+#define EPITCNR				0x10
+
+#define EPITCR_EN			BIT(0)
+#define EPITCR_ENMOD			BIT(1)
+#define EPITCR_OCIEN			BIT(2)
+#define EPITCR_RLD			BIT(3)
+#define EPITCR_PRESC(x)			(((x) & 0xfff) << 4)
+#define EPITCR_SWR			BIT(16)
+#define EPITCR_IOVW			BIT(17)
+#define EPITCR_DBGEN			BIT(18)
+#define EPITCR_WAITEN			BIT(19)
+#define EPITCR_RES			BIT(20)
+#define EPITCR_STOPEN			BIT(21)
+#define EPITCR_OM_DISCON		(0 << 22)
+#define EPITCR_OM_TOGGLE		(1 << 22)
+#define EPITCR_OM_CLEAR			(2 << 22)
+#define EPITCR_OM_SET			(3 << 22)
+#define EPITCR_CLKSRC_OFF		(0 << 24)
+#define EPITCR_CLKSRC_PERIPHERAL	(1 << 24)
+#define EPITCR_CLKSRC_REF_HIGH		(2 << 24)
+#define EPITCR_CLKSRC_REF_LOW		(3 << 24)
+
+#define EPITSR_OCIF			BIT(0)
+
+struct epit_timer {
+	void __iomem *base;
+	int irq;
+	struct clk *clk;
+	struct clock_event_device ced;
+	struct irqaction act;
+};
+
+static void __iomem *sched_clock_reg;
+
+static inline struct epit_timer *to_epit_timer(struct clock_event_device *ced)
+{
+	return container_of(ced, struct epit_timer, ced);
+}
+
+static inline void epit_irq_disable(struct epit_timer *epittm)
+{
+	u32 val;
+
+	val = readl_relaxed(epittm->base + EPITCR);
+	writel_relaxed(val & ~EPITCR_OCIEN, epittm->base + EPITCR);
+}
+
+static inline void epit_irq_enable(struct epit_timer *epittm)
+{
+	u32 val;
+
+	val = readl_relaxed(epittm->base + EPITCR);
+	writel_relaxed(val | EPITCR_OCIEN, epittm->base + EPITCR);
+}
+
+static void epit_irq_acknowledge(struct epit_timer *epittm)
+{
+	writel_relaxed(EPITSR_OCIF, epittm->base + EPITSR);
+}
+
+static u64 notrace epit_read_sched_clock(void)
+{
+	return ~readl_relaxed(sched_clock_reg);
+}
+
+static int epit_set_next_event(unsigned long cycles,
+			       struct clock_event_device *ced)
+{
+	struct epit_timer *epittm = to_epit_timer(ced);
+	unsigned long tcmp;
+
+	tcmp = readl_relaxed(epittm->base + EPITCNR) - cycles;
+	writel_relaxed(tcmp, epittm->base + EPITCMPR);
+
+	return 0;
+}
+
+/* Left event sources disabled, no more interrupts appear */
+static int epit_shutdown(struct clock_event_device *ced)
+{
+	struct epit_timer *epittm = to_epit_timer(ced);
+	unsigned long flags;
+
+	/*
+	 * The timer interrupt generation is disabled at least
+	 * for enough time to call epit_set_next_event()
+	 */
+	local_irq_save(flags);
+
+	/* Disable interrupt in EPIT module */
+	epit_irq_disable(epittm);
+
+	/* Clear pending interrupt */
+	epit_irq_acknowledge(epittm);
+
+	local_irq_restore(flags);
+
+	return 0;
+}
+
+static int epit_set_oneshot(struct clock_event_device *ced)
+{
+	struct epit_timer *epittm = to_epit_timer(ced);
+	unsigned long flags;
+
+	/*
+	 * The timer interrupt generation is disabled at least
+	 * for enough time to call epit_set_next_event()
+	 */
+	local_irq_save(flags);
+
+	/* Disable interrupt in EPIT module */
+	epit_irq_disable(epittm);
+
+	/* Clear pending interrupt, only while switching mode */
+	if (!clockevent_state_oneshot(ced))
+		epit_irq_acknowledge(epittm);
+
+	/*
+	 * Do not put overhead of interrupt enable/disable into
+	 * epit_set_next_event(), the core has about 4 minutes
+	 * to call epit_set_next_event() or shutdown clock after
+	 * mode switching
+	 */
+	epit_irq_enable(epittm);
+	local_irq_restore(flags);
+
+	return 0;
+}
+
+static irqreturn_t epit_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *ced = dev_id;
+	struct epit_timer *epittm = to_epit_timer(ced);
+
+	epit_irq_acknowledge(epittm);
+
+	ced->event_handler(ced);
+
+	return IRQ_HANDLED;
+}
+
+static int __init epit_clocksource_init(struct epit_timer *epittm)
+{
+	unsigned int c = clk_get_rate(epittm->clk);
+
+	sched_clock_reg = epittm->base + EPITCNR;
+	sched_clock_register(epit_read_sched_clock, 32, c);
+
+	return clocksource_mmio_init(epittm->base + EPITCNR, "epit", c, 200, 32,
+				     clocksource_mmio_readl_down);
+}
+
+static int __init epit_clockevent_init(struct epit_timer *epittm)
+{
+	struct clock_event_device *ced = &epittm->ced;
+	struct irqaction *act = &epittm->act;
+
+	ced->name = "epit";
+	ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ;
+	ced->set_state_shutdown = epit_shutdown;
+	ced->tick_resume = epit_shutdown;
+	ced->set_state_oneshot = epit_set_oneshot;
+	ced->set_next_event = epit_set_next_event;
+	ced->rating = 200;
+	ced->cpumask = cpumask_of(0);
+	ced->irq = epittm->irq;
+	clockevents_config_and_register(ced, clk_get_rate(epittm->clk),
+					0xff, 0xfffffffe);
+
+	act->name = "i.MX EPIT Timer Tick",
+	act->flags = IRQF_TIMER | IRQF_IRQPOLL;
+	act->handler = epit_timer_interrupt;
+	act->dev_id = ced;
+
+	/* Make irqs happen */
+	return setup_irq(epittm->irq, act);
+}
+
+static int __init epit_timer_init(struct device_node *np)
+{
+	struct epit_timer *epittm;
+	int ret;
+
+	epittm = kzalloc(sizeof(*epittm), GFP_KERNEL);
+	if (!epittm)
+		return -ENOMEM;
+
+	epittm->base = of_iomap(np, 0);
+	if (!epittm->base) {
+		ret = -ENXIO;
+		goto out_kfree;
+	}
+
+	epittm->irq = irq_of_parse_and_map(np, 0);
+	if (!epittm->irq) {
+		ret = -EINVAL;
+		goto out_iounmap;
+	}
+
+        /* Get EPIT clock */
+        epittm->clk = of_clk_get(np, 0);
+        if (IS_ERR(epittm->clk)) {
+		pr_err("i.MX EPIT: unable to get clk\n");
+		ret = PTR_ERR(epittm->clk);
+		goto out_iounmap;
+        }
+
+	ret = clk_prepare_enable(epittm->clk);
+	if (ret) {
+		pr_err("i.MX EPIT: unable to prepare+enable clk\n");
+		goto out_iounmap;
+	}
+
+	/* Initialise to a known state (all timers off, and timing reset) */
+	writel_relaxed(0x0, epittm->base + EPITCR);
+	writel_relaxed(0xffffffff, epittm->base + EPITLR);
+	writel_relaxed(EPITCR_EN | EPITCR_CLKSRC_REF_HIGH | EPITCR_WAITEN,
+		       epittm->base + EPITCR);
+
+	ret = epit_clocksource_init(epittm);
+	if (ret) {
+		pr_err("i.MX EPIT: failed to init clocksource\n");
+		goto out_clk_disable;
+	}
+
+	ret = epit_clockevent_init(epittm);
+	if (ret) {
+		pr_err("i.MX EPIT: failed to init clockevent\n");
+		goto out_clk_disable;
+	}
+
+	return 0;
+
+out_clk_disable:
+	clk_disable_unprepare(epittm->clk);
+out_iounmap:
+	iounmap(epittm->base);
+out_kfree:
+	kfree(epittm);
+
+	return ret;
+}
+TIMER_OF_DECLARE(epit_timer, "fsl,imx31-epit", epit_timer_init);