powerpc/qe: Implement QE Pin Multiplexing API

With this API we're able to set a QE pin to the GPIO mode or a dedicated
peripheral function.

The API relies on the fact that QE gpio controllers are registered. If
they aren't, the API won't work (gracefully though).

There is one caveat though: if anybody occupied the node->data before us,
or overwrote it, then bad things will happen. Luckily this is all in the
platform code that we fully control, so this should never happen.

I could implement more checks (for example we could create a list of
successfully registered QE controllers, and compare the node->data in the
qe_pin_request()), but this is unneeded if nobody is going to do silly
things behind our back.

Signed-off-by: Anton Vorontsov <[e-mail]>
Signed-off-by: Kumar Gala <[e-mail]>

arch/powerpc/include/asm/qe.h

···
 #ifdef __KERNEL__
 
 #include <linux/spinlock.h>
+#include <linux/errno.h>
+#include <linux/err.h>
 #include <asm/cpm.h>
 #include <asm/immap_qe.h>
 
···
 extern int par_io_config_pin(u8 port, u8 pin, int dir, int open_drain,
 			     int assignment, int has_irq);
 extern int par_io_data_set(u8 port, u8 pin, u8 val);
+
+/*
+ * Pin multiplexing functions.
+ */
+struct qe_pin;
+#ifdef CONFIG_QE_GPIO
+extern struct qe_pin *qe_pin_request(struct device_node *np, int index);
+extern void qe_pin_free(struct qe_pin *qe_pin);
+extern void qe_pin_set_gpio(struct qe_pin *qe_pin);
+extern void qe_pin_set_dedicated(struct qe_pin *pin);
+#else
+static inline struct qe_pin *qe_pin_request(struct device_node *np, int index)
+{
+	return ERR_PTR(-ENOSYS);
+}
+static inline void qe_pin_free(struct qe_pin *qe_pin) {}
+static inline void qe_pin_set_gpio(struct qe_pin *qe_pin) {}
+static inline void qe_pin_set_dedicated(struct qe_pin *pin) {}
+#endif /* CONFIG_QE_GPIO */
 
 /* QE internal API */
 int qe_issue_cmd(u32 cmd, u32 device, u8 mcn_protocol, u32 cmd_input);

arch/powerpc/sysdev/qe_lib/gpio.c

···
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/spinlock.h>
+#include <linux/err.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/of_gpio.h>
···
 	struct of_mm_gpio_chip mm_gc;
 	spinlock_t lock;
 
+	unsigned long pin_flags[QE_PIO_PINS];
+#define QE_PIN_REQUESTED 0
+
 	/* shadowed data register to clear/set bits safely */
 	u32 cpdata;
+
+	/* saved_regs used to restore dedicated functions */
+	struct qe_pio_regs saved_regs;
 };
 
 static inline struct qe_gpio_chip *
···
 	struct qe_pio_regs __iomem *regs = mm_gc->regs;
 
 	qe_gc->cpdata = in_be32(&regs->cpdata);
+	qe_gc->saved_regs.cpdata = qe_gc->cpdata;
+	qe_gc->saved_regs.cpdir1 = in_be32(&regs->cpdir1);
+	qe_gc->saved_regs.cpdir2 = in_be32(&regs->cpdir2);
+	qe_gc->saved_regs.cppar1 = in_be32(&regs->cppar1);
+	qe_gc->saved_regs.cppar2 = in_be32(&regs->cppar2);
+	qe_gc->saved_regs.cpodr = in_be32(&regs->cpodr);
 }
 
 static int qe_gpio_get(struct gpio_chip *gc, unsigned int gpio)
···
 
 	return 0;
 }
+
+struct qe_pin {
+	/*
+	 * The qe_gpio_chip name is unfortunate, we should change that to
+	 * something like qe_pio_controller. Someday.
+	 */
+	struct qe_gpio_chip *controller;
+	int num;
+};
+
+/**
+ * qe_pin_request - Request a QE pin
+ * @np:		device node to get a pin from
+ * @index:	index of a pin in the device tree
+ * Context:	non-atomic
+ *
+ * This function return qe_pin so that you could use it with the rest of
+ * the QE Pin Multiplexing API.
+ */
+struct qe_pin *qe_pin_request(struct device_node *np, int index)
+{
+	struct qe_pin *qe_pin;
+	struct device_node *gc;
+	struct of_gpio_chip *of_gc = NULL;
+	struct of_mm_gpio_chip *mm_gc;
+	struct qe_gpio_chip *qe_gc;
+	int err;
+	int size;
+	const void *gpio_spec;
+	const u32 *gpio_cells;
+	unsigned long flags;
+
+	qe_pin = kzalloc(sizeof(*qe_pin), GFP_KERNEL);
+	if (!qe_pin) {
+		pr_debug("%s: can't allocate memory\n", __func__);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	err = of_parse_phandles_with_args(np, "gpios", "#gpio-cells", index,
+					  &gc, &gpio_spec);
+	if (err) {
+		pr_debug("%s: can't parse gpios property\n", __func__);
+		goto err0;
+	}
+
+	if (!of_device_is_compatible(gc, "fsl,mpc8323-qe-pario-bank")) {
+		pr_debug("%s: tried to get a non-qe pin\n", __func__);
+		err = -EINVAL;
+		goto err1;
+	}
+
+	of_gc = gc->data;
+	if (!of_gc) {
+		pr_debug("%s: gpio controller %s isn't registered\n",
+			 np->full_name, gc->full_name);
+		err = -ENODEV;
+		goto err1;
+	}
+
+	gpio_cells = of_get_property(gc, "#gpio-cells", &size);
+	if (!gpio_cells || size != sizeof(*gpio_cells) ||
+			*gpio_cells != of_gc->gpio_cells) {
+		pr_debug("%s: wrong #gpio-cells for %s\n",
+			 np->full_name, gc->full_name);
+		err = -EINVAL;
+		goto err1;
+	}
+
+	err = of_gc->xlate(of_gc, np, gpio_spec, NULL);
+	if (err < 0)
+		goto err1;
+
+	mm_gc = to_of_mm_gpio_chip(&of_gc->gc);
+	qe_gc = to_qe_gpio_chip(mm_gc);
+
+	spin_lock_irqsave(&qe_gc->lock, flags);
+
+	if (test_and_set_bit(QE_PIN_REQUESTED, &qe_gc->pin_flags[err]) == 0) {
+		qe_pin->controller = qe_gc;
+		qe_pin->num = err;
+		err = 0;
+	} else {
+		err = -EBUSY;
+	}
+
+	spin_unlock_irqrestore(&qe_gc->lock, flags);
+
+	if (!err)
+		return qe_pin;
+err1:
+	of_node_put(gc);
+err0:
+	kfree(qe_pin);
+	pr_debug("%s failed with status %d\n", __func__, err);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL(qe_pin_request);
+
+/**
+ * qe_pin_free - Free a pin
+ * @qe_pin:	pointer to the qe_pin structure
+ * Context:	any
+ *
+ * This function frees the qe_pin structure and makes a pin available
+ * for further qe_pin_request() calls.
+ */
+void qe_pin_free(struct qe_pin *qe_pin)
+{
+	struct qe_gpio_chip *qe_gc = qe_pin->controller;
+	unsigned long flags;
+	const int pin = qe_pin->num;
+
+	spin_lock_irqsave(&qe_gc->lock, flags);
+	test_and_clear_bit(QE_PIN_REQUESTED, &qe_gc->pin_flags[pin]);
+	spin_unlock_irqrestore(&qe_gc->lock, flags);
+
+	kfree(qe_pin);
+}
+EXPORT_SYMBOL(qe_pin_free);
+
+/**
+ * qe_pin_set_dedicated - Revert a pin to a dedicated peripheral function mode
+ * @qe_pin:	pointer to the qe_pin structure
+ * Context:	any
+ *
+ * This function resets a pin to a dedicated peripheral function that
+ * has been set up by the firmware.
+ */
+void qe_pin_set_dedicated(struct qe_pin *qe_pin)
+{
+	struct qe_gpio_chip *qe_gc = qe_pin->controller;
+	struct qe_pio_regs __iomem *regs = qe_gc->mm_gc.regs;
+	struct qe_pio_regs *sregs = &qe_gc->saved_regs;
+	int pin = qe_pin->num;
+	u32 mask1 = 1 << (QE_PIO_PINS - (pin + 1));
+	u32 mask2 = 0x3 << (QE_PIO_PINS - (pin % (QE_PIO_PINS / 2) + 1) * 2);
+	bool second_reg = pin > (QE_PIO_PINS / 2) - 1;
+	unsigned long flags;
+
+	spin_lock_irqsave(&qe_gc->lock, flags);
+
+	if (second_reg) {
+		clrsetbits_be32(&regs->cpdir2, mask2, sregs->cpdir2 & mask2);
+		clrsetbits_be32(&regs->cppar2, mask2, sregs->cppar2 & mask2);
+	} else {
+		clrsetbits_be32(&regs->cpdir1, mask2, sregs->cpdir1 & mask2);
+		clrsetbits_be32(&regs->cppar1, mask2, sregs->cppar1 & mask2);
+	}
+
+	if (sregs->cpdata & mask1)
+		qe_gc->cpdata |= mask1;
+	else
+		qe_gc->cpdata &= ~mask1;
+
+	out_be32(&regs->cpdata, qe_gc->cpdata);
+	clrsetbits_be32(&regs->cpodr, mask1, sregs->cpodr & mask1);
+
+	spin_unlock_irqrestore(&qe_gc->lock, flags);
+}
+EXPORT_SYMBOL(qe_pin_set_dedicated);
+
+/**
+ * qe_pin_set_gpio - Set a pin to the GPIO mode
+ * @qe_pin:	pointer to the qe_pin structure
+ * Context:	any
+ *
+ * This function sets a pin to the GPIO mode.
+ */
+void qe_pin_set_gpio(struct qe_pin *qe_pin)
+{
+	struct qe_gpio_chip *qe_gc = qe_pin->controller;
+	struct qe_pio_regs __iomem *regs = qe_gc->mm_gc.regs;
+	unsigned long flags;
+
+	spin_lock_irqsave(&qe_gc->lock, flags);
+
+	/* Let's make it input by default, GPIO API is able to change that. */
+	__par_io_config_pin(regs, qe_pin->num, QE_PIO_DIR_IN, 0, 0, 0);
+
+	spin_unlock_irqrestore(&qe_gc->lock, flags);
+}
+EXPORT_SYMBOL(qe_pin_set_gpio);
 
 static int __init qe_add_gpiochips(void)
 {