usb: gadget: pch_udc: Convert to use GPIO descriptors

This switches the PCH UDC driver to use GPIO descriptors. The way
this is supposed to be used is confusing. The code contains the
following:

/* GPIO port for VBUS detecting */
static int vbus_gpio_port = -1; /* GPIO port number (-1:Not used) */

So a hardcoded GPIO number in the code. Further the probe() path
very clearly will exit if the GPIO is not found, so this driver
can only be configured by editing the code, hard-coding a GPIO
number into this variable.

This is simply not how we do things. My guess is that this is
used in products by patching a GPIO number into this variable and
shipping a kernel that is compile-time tailored for the target
system.

I switched this mechanism to using a GPIO descriptor associated
with the parent PCI device. This can be added by using the 16bit
subsystem ID or similar to identify which exact machine we are
running on and what GPIO is present on that machine, and then
add a GPIO descriptor using gpiod_add_lookup_table() from
<linux/gpio/machine.h>. Since I don't have any target systems
I cannot add this but I'm happy to help. I put in a FIXME so
the people actually using this driver knows what to do.

Cc: Felipe Balbi <[e-mail]>
Tested-by: Andy Shevchenko <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/gadget/udc/pch_udc.c

···
 #include <linux/interrupt.h>
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
-#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/irq.h>
-
-/* GPIO port for VBUS detecting */
-static int vbus_gpio_port = -1;		/* GPIO port number (-1:Not used) */
 
 #define PCH_VBUS_PERIOD		3000	/* VBUS polling period (msec) */
 #define PCH_VBUS_INTERVAL	10	/* VBUS polling interval (msec) */
···
 /**
  * struct pch_vbus_gpio_data - Structure holding GPIO informaton
  *					for detecting VBUS
- * @port:		gpio port number
+ * @port:		gpio descriptor for the VBUS GPIO
  * @intr:		gpio interrupt number
  * @irq_work_fall:	Structure for WorkQueue
  * @irq_work_rise:	Structure for WorkQueue
  */
 struct pch_vbus_gpio_data {
-	int			port;
+	struct gpio_desc	*port;
 	int			intr;
 	struct work_struct	irq_work_fall;
 	struct work_struct	irq_work_rise;
···
 	int vbus = 0;
 
 	if (dev->vbus_gpio.port)
-		vbus = gpio_get_value(dev->vbus_gpio.port) ? 1 : 0;
+		vbus = gpiod_get_value(dev->vbus_gpio.port) ? 1 : 0;
 	else
 		vbus = -1;
 
···
 /**
  * pch_vbus_gpio_init() - This API initializes GPIO port detecting VBUS.
  * @dev:		Reference to the driver structure
- * @vbus_gpio_port:	Number of GPIO port to detect gpio
  *
  * Return codes:
  *	0: Success
  *	-EINVAL: GPIO port is invalid or can't be initialized.
  */
-static int pch_vbus_gpio_init(struct pch_udc_dev *dev, int vbus_gpio_port)
+static int pch_vbus_gpio_init(struct pch_udc_dev *dev)
 {
 	int err;
 	int irq_num = 0;
+	struct gpio_desc *gpiod;
 
-	dev->vbus_gpio.port = 0;
+	dev->vbus_gpio.port = NULL;
 	dev->vbus_gpio.intr = 0;
 
-	if (vbus_gpio_port <= -1)
-		return -EINVAL;
+	/* Retrieve the GPIO line from the USB gadget device */
+	gpiod = devm_gpiod_get(dev->gadget.dev.parent, NULL, GPIOD_IN);
+	if (IS_ERR(gpiod))
+		return PTR_ERR(gpiod);
+	gpiod_set_consumer_name(gpiod, "pch_vbus");
 
-	err = gpio_is_valid(vbus_gpio_port);
-	if (!err) {
-		pr_err("%s: gpio port %d is invalid\n",
-			__func__, vbus_gpio_port);
-		return -EINVAL;
-	}
-
-	err = gpio_request(vbus_gpio_port, "pch_vbus");
-	if (err) {
-		pr_err("%s: can't request gpio port %d, err: %d\n",
-			__func__, vbus_gpio_port, err);
-		return -EINVAL;
-	}
-
-	dev->vbus_gpio.port = vbus_gpio_port;
-	gpio_direction_input(vbus_gpio_port);
+	dev->vbus_gpio.port = gpiod;
 	INIT_WORK(&dev->vbus_gpio.irq_work_fall, pch_vbus_gpio_work_fall);
 
-	irq_num = gpio_to_irq(vbus_gpio_port);
+	irq_num = gpiod_to_irq(gpiod);
 	if (irq_num > 0) {
 		irq_set_irq_type(irq_num, IRQ_TYPE_EDGE_BOTH);
 		err = request_irq(irq_num, pch_vbus_gpio_irq, 0,
···
 {
 	if (dev->vbus_gpio.intr)
 		free_irq(dev->vbus_gpio.intr, dev);
-
-	if (dev->vbus_gpio.port)
-		gpio_free(dev->vbus_gpio.port);
 }
 
 /**
···
 {
 	pch_udc_init(dev);
 	pch_udc_pcd_reinit(dev);
-	pch_vbus_gpio_init(dev, vbus_gpio_port);
+	pch_vbus_gpio_init(dev);
 	return 0;
 }
 
···
 		return retval;
 
 	dev->base_addr = pcim_iomap_table(pdev)[bar];
+
+	/*
+	 * FIXME: add a GPIO descriptor table to pdev.dev using
+	 * gpiod_add_descriptor_table() from <linux/gpio/machine.h> based on
+	 * the PCI subsystem ID. The system-dependent GPIO is necessary for
+	 * VBUS operation.
+	 */
 
 	/* initialize the hardware */
 	if (pch_udc_pcd_init(dev))