counter: ti-eqep: implement over/underflow events

This adds support to the TI eQEP counter driver for subscribing to
overflow and underflow events using the counter chrdev interface.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20240609-counter-ti-eqep-over-under-events-v1-1-74fe1632f5ab@baylibre.com
Signed-off-by: William Breathitt Gray <wbg@kernel.org>

drivers/counter/ti-eqep.c

@@ -8,6 +8,7 @@
 #include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/counter.h>
+#include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
@@ -68,6 +69,44 @@
 #define QEPCTL_UTE		BIT(1)
 #define QEPCTL_WDE		BIT(0)
 
+#define QEINT_UTO		BIT(11)
+#define QEINT_IEL		BIT(10)
+#define QEINT_SEL		BIT(9)
+#define QEINT_PCM		BIT(8)
+#define QEINT_PCR		BIT(7)
+#define QEINT_PCO		BIT(6)
+#define QEINT_PCU		BIT(5)
+#define QEINT_WTO		BIT(4)
+#define QEINT_QDC		BIT(3)
+#define QEINT_PHE		BIT(2)
+#define QEINT_PCE		BIT(1)
+
+#define QFLG_UTO		BIT(11)
+#define QFLG_IEL		BIT(10)
+#define QFLG_SEL		BIT(9)
+#define QFLG_PCM		BIT(8)
+#define QFLG_PCR		BIT(7)
+#define QFLG_PCO		BIT(6)
+#define QFLG_PCU		BIT(5)
+#define QFLG_WTO		BIT(4)
+#define QFLG_QDC		BIT(3)
+#define QFLG_PHE		BIT(2)
+#define QFLG_PCE		BIT(1)
+#define QFLG_INT		BIT(0)
+
+#define QCLR_UTO		BIT(11)
+#define QCLR_IEL		BIT(10)
+#define QCLR_SEL		BIT(9)
+#define QCLR_PCM		BIT(8)
+#define QCLR_PCR		BIT(7)
+#define QCLR_PCO		BIT(6)
+#define QCLR_PCU		BIT(5)
+#define QCLR_WTO		BIT(4)
+#define QCLR_QDC		BIT(3)
+#define QCLR_PHE		BIT(2)
+#define QCLR_PCE		BIT(1)
+#define QCLR_INT		BIT(0)
+
 /* EQEP Inputs */
 enum {
 	TI_EQEP_SIGNAL_QEPA,	/* QEPA/XCLK */
@@ -239,12 +278,49 @@ static int ti_eqep_action_read(struct counter_device *counter,
 	}
 }
 
+static int ti_eqep_events_configure(struct counter_device *counter)
+{
+	struct ti_eqep_cnt *priv = counter_priv(counter);
+	struct counter_event_node *event_node;
+	u32 qeint = 0;
+
+	list_for_each_entry(event_node, &counter->events_list, l) {
+		switch (event_node->event) {
+		case COUNTER_EVENT_OVERFLOW:
+			qeint |= QEINT_PCO;
+			break;
+		case COUNTER_EVENT_UNDERFLOW:
+			qeint |= QEINT_PCU;
+			break;
+		}
+	}
+
+	return regmap_write(priv->regmap16, QEINT, qeint);
+}
+
+static int ti_eqep_watch_validate(struct counter_device *counter,
+				  const struct counter_watch *watch)
+{
+	switch (watch->event) {
+	case COUNTER_EVENT_OVERFLOW:
+	case COUNTER_EVENT_UNDERFLOW:
+		if (watch->channel != 0)
+			return -EINVAL;
+
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
 static const struct counter_ops ti_eqep_counter_ops = {
 	.count_read	= ti_eqep_count_read,
 	.count_write	= ti_eqep_count_write,
 	.function_read	= ti_eqep_function_read,
 	.function_write	= ti_eqep_function_write,
 	.action_read	= ti_eqep_action_read,
+	.events_configure = ti_eqep_events_configure,
+	.watch_validate	= ti_eqep_watch_validate,
 };
 
 static int ti_eqep_position_ceiling_read(struct counter_device *counter,
@@ -355,6 +431,25 @@ static struct counter_count ti_eqep_counts[] = {
 	},
 };
 
+static irqreturn_t ti_eqep_irq_handler(int irq, void *dev_id)
+{
+	struct counter_device *counter = dev_id;
+	struct ti_eqep_cnt *priv = counter_priv(counter);
+	u32 qflg;
+
+	regmap_read(priv->regmap16, QFLG, &qflg);
+
+	if (qflg & QFLG_PCO)
+		counter_push_event(counter, COUNTER_EVENT_OVERFLOW, 0);
+
+	if (qflg & QFLG_PCU)
+		counter_push_event(counter, COUNTER_EVENT_UNDERFLOW, 0);
+
+	regmap_write(priv->regmap16, QCLR, qflg);
+
+	return IRQ_HANDLED;
+}
+
 static const struct regmap_config ti_eqep_regmap32_config = {
 	.name = "32-bit",
 	.reg_bits = 32,
@@ -378,7 +473,7 @@ static int ti_eqep_probe(struct platform_device *pdev)
 	struct ti_eqep_cnt *priv;
 	void __iomem *base;
 	struct clk *clk;
-	int err;
+	int err, irq;
 
 	counter = devm_counter_alloc(dev, sizeof(*priv));
 	if (!counter)
@@ -399,6 +494,15 @@ static int ti_eqep_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->regmap16))
 		return PTR_ERR(priv->regmap16);
 
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	err = devm_request_threaded_irq(dev, irq, NULL, ti_eqep_irq_handler,
+					IRQF_ONESHOT, dev_name(dev), counter);
+	if (err < 0)
+		return dev_err_probe(dev, err, "failed to request IRQ\n");
+
 	counter->name = dev_name(dev);
 	counter->parent = dev;
 	counter->ops = &ti_eqep_counter_ops;