gpio: pmic_eic: Add edge trigger emulation for PMIC EIC

This patch will toggle the EIC level to emulate the edge trigger to
support PMIC EIC egdge trigger function, which is required by gpio-keys
driver.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-pmic-eic-sprd.c

@@ -178,6 +178,14 @@ static int sprd_pmic_eic_irq_set_type(struct irq_data *data,
 	case IRQ_TYPE_LEVEL_LOW:
 		pmic_eic->reg[REG_IEV] = 0;
 		break;
+	case IRQ_TYPE_EDGE_RISING:
+	case IRQ_TYPE_EDGE_FALLING:
+	case IRQ_TYPE_EDGE_BOTH:
+		/*
+		 * Will set the trigger level according to current EIC level
+		 * in irq_bus_sync_unlock() interface, so here nothing to do.
+		 */
+		break;
 	default:
 		return -ENOTSUPP;
 	}
@@ -197,11 +205,22 @@ static void sprd_pmic_eic_bus_sync_unlock(struct irq_data *data)
 {
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
 	struct sprd_pmic_eic *pmic_eic = gpiochip_get_data(chip);
+	u32 trigger = irqd_get_trigger_type(data);
 	u32 offset = irqd_to_hwirq(data);
+	int state;
 
 	/* Set irq type */
-	sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_IEV,
-			     pmic_eic->reg[REG_IEV]);
+	if (trigger & IRQ_TYPE_EDGE_BOTH) {
+		state = sprd_pmic_eic_get(chip, offset);
+		if (state)
+			sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_IEV, 0);
+		else
+			sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_IEV, 1);
+	} else {
+		sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_IEV,
+				     pmic_eic->reg[REG_IEV]);
+	}
+
 	/* Set irq unmask */
 	sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_IE,
 			     pmic_eic->reg[REG_IE]);
@@ -212,6 +231,35 @@ static void sprd_pmic_eic_bus_sync_unlock(struct irq_data *data)
 	mutex_unlock(&pmic_eic->buslock);
 }
 
+static void sprd_pmic_eic_toggle_trigger(struct gpio_chip *chip,
+					 unsigned int irq, unsigned int offset)
+{
+	u32 trigger = irq_get_trigger_type(irq);
+	int state, post_state;
+
+	if (!(trigger & IRQ_TYPE_EDGE_BOTH))
+		return;
+
+	state = sprd_pmic_eic_get(chip, offset);
+retry:
+	if (state)
+		sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_IEV, 0);
+	else
+		sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_IEV, 1);
+
+	post_state = sprd_pmic_eic_get(chip, offset);
+	if (state != post_state) {
+		dev_warn(chip->parent, "PMIC EIC level was changed.\n");
+		state = post_state;
+		goto retry;
+	}
+
+	/* Set irq unmask */
+	sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_IE, 1);
+	/* Generate trigger start pulse for debounce EIC */
+	sprd_pmic_eic_update(chip, offset, SPRD_PMIC_EIC_TRIG, 1);
+}
+
 static irqreturn_t sprd_pmic_eic_irq_handler(int irq, void *data)
 {
 	struct sprd_pmic_eic *pmic_eic = data;
@@ -233,6 +281,12 @@ static irqreturn_t sprd_pmic_eic_irq_handler(int irq, void *data)
 
 		girq = irq_find_mapping(chip->irq.domain, n);
 		handle_nested_irq(girq);
+
+		/*
+		 * The PMIC EIC can only support level trigger, so we can
+		 * toggle the level trigger to emulate the edge trigger.
+		 */
+		sprd_pmic_eic_toggle_trigger(chip, girq, n);
 	}
 
 	return IRQ_HANDLED;