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

Clément Péron
2018-06-11T12:42:21Z

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);