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 <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

2 files changed, 216 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/qe.h b/arch/powerpc/include/asm/qe.h
index edee15d269ea..32274407b93a 100644
--- a/arch/powerpc/include/asm/qe.h
+++ b/arch/powerpc/include/asm/qe.h
@@ -17,6 +17,8 @@
 #ifdef __KERNEL__
 
 #include <linux/spinlock.h>
+#include <linux/errno.h>
+#include <linux/err.h>
 #include <asm/cpm.h>
 #include <asm/immap_qe.h>
 
@@ -112,6 +114,25 @@ 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);
 enum qe_clock qe_clock_source(const char *source);
diff --git a/arch/powerpc/sysdev/qe_lib/gpio.c b/arch/powerpc/sysdev/qe_lib/gpio.c
index 8e5a0bc36d0b..3485288dce31 100644
--- a/arch/powerpc/sysdev/qe_lib/gpio.c
+++ b/arch/powerpc/sysdev/qe_lib/gpio.c
@@ -14,6 +14,7 @@
 #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>
@@ -24,8 +25,14 @@ struct qe_gpio_chip {
         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 *
@@ -40,6 +47,12 @@ static void qe_gpio_save_regs(struct of_mm_gpio_chip *mm_gc)
         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)
@@ -103,6 +116,188 @@ static int qe_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
         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)
 {
         struct device_node *np;