Hi Stefan,

quoted

+
+#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

quoted

+
+     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);