usb: ohci-da8xx: disable the regulator if the overcurrent irq fired

Historically the power supply management in this driver has been handled
in two separate places in parallel. Device-tree users simply defined an
appropriate regulator, while two boards with no DT support (da830-evm and
omapl138-hawk) passed functions defined in their respective board files
over platform data. These functions simply used legacy GPIO calls to
watch the oc GPIO for interrupts and disable the vbus GPIO when the irq
fires.

Commit d193abf1 ("usb: ohci-da8xx: add vbus and overcurrent gpios")
updated these GPIO calls to the modern API and moved them inside the
driver.

This however is not the optimal solution for the vbus GPIO which should
be modeled as a fixed regulator that can be controlled with a GPIO.

In order to keep the overcurrent protection available once we move the
board files to using fixed regulators we need to disable the enable_reg
regulator when the overcurrent indicator interrupt fires. Since we
cannot call regulator_disable() from interrupt context, we need to
switch to using a oneshot threaded interrupt.
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>

drivers/usb/host/ohci-da8xx.c

@@ -202,12 +202,23 @@ static int ohci_da8xx_regulator_event(struct notifier_block *nb,
 	return 0;
 }
 
-static irqreturn_t ohci_da8xx_oc_handler(int irq, void *data)
+static irqreturn_t ohci_da8xx_oc_thread(int irq, void *data)
 {
 	struct da8xx_ohci_hcd *da8xx_ohci = data;
+	struct device *dev = da8xx_ohci->hcd->self.controller;
+	int ret;
 
-	if (gpiod_get_value(da8xx_ohci->oc_gpio))
-		gpiod_set_value(da8xx_ohci->vbus_gpio, 0);
+	if (gpiod_get_value_cansleep(da8xx_ohci->oc_gpio)) {
+		if (da8xx_ohci->vbus_gpio) {
+			gpiod_set_value_cansleep(da8xx_ohci->vbus_gpio, 0);
+		} else if (da8xx_ohci->vbus_reg) {
+			ret = regulator_disable(da8xx_ohci->vbus_reg);
+			if (ret)
+				dev_err(dev,
+					"Failed to disable regulator: %d\n",
+					ret);
+		}
+	}
 
 	return IRQ_HANDLED;
 }
@@ -434,8 +445,9 @@ static int ohci_da8xx_probe(struct platform_device *pdev)
 		if (oc_irq < 0)
 			goto err;
 
-		error = devm_request_irq(dev, oc_irq, ohci_da8xx_oc_handler,
-				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+		error = devm_request_threaded_irq(dev, oc_irq, NULL,
+				ohci_da8xx_oc_thread, IRQF_TRIGGER_RISING |
+				IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
 				"OHCI over-current indicator", da8xx_ohci);
 		if (error)
 			goto err;