pinctrl: allow concurrent gpio and mux function ownership of pins

Per recent updates to Documentation/gpio.txt, gpiolib drivers should
inform pinctrl when a GPIO is requested. pinctrl then marks that pin as
in-use for that GPIO function.

When an SoC muxes pins in a group, it's quite possible for the group to
contain e.g. 6 pins, but only 4 of them actually be needed by the HW
module that's mux'd to them. In this case, the other 2 pins could be
used as GPIOs. However, pinctrl marks all the pins within the group as
in-use by the selected mux function. To allow the expected gpiolib
interaction, separate the concepts of pin ownership into two parts: One
for the mux function and one for GPIO usage. Finally, allow those two
ownerships to exist in parallel.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

2 files changed, 56 insertions, 29 deletions

diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h
index efbfb62ab147..17ecf651b123 100644
--- a/drivers/pinctrl/core.h
+++ b/drivers/pinctrl/core.h
@@ -119,15 +119,15 @@ struct pinctrl_setting {
  * @name: a name for the pin, e.g. the name of the pin/pad/finger on a
  *      datasheet or such
  * @dynamic_name: if the name of this pin was dynamically allocated
- * @usecount: If zero, the pin is not claimed, and @owner should be NULL.
+ * @mux_usecount: If zero, the pin is not claimed, and @owner should be NULL.
  *      If non-zero, this pin is claimed by @owner. This field is an integer
  *      rather than a boolean, since pinctrl_get() might process multiple
  *      mapping table entries that refer to, and hence claim, the same group
  *      or pin, and each of these will increment the @usecount.
- * @owner: The name of the entity owning the pin. Typically, this is the name
- *      of the device that called pinctrl_get(). Alternatively, it may be the
- *      name of the GPIO passed to pinctrl_request_gpio().
+ * @mux_owner: The name of device that called pinctrl_get().
  * @mux_setting: The most recent selected mux setting for this pin, if any.
+ * @gpio_owner: If pinctrl_request_gpio() was called for this pin, this is
+ *      the name of the GPIO that "owns" this pin.
  */
 struct pin_desc {
         struct pinctrl_dev *pctldev;
@@ -135,9 +135,10 @@ struct pin_desc {
         bool dynamic_name;
         /* These fields only added when supporting pinmux drivers */
 #ifdef CONFIG_PINMUX
-        unsigned usecount;
-        const char *owner;
+        unsigned mux_usecount;
+        const char *mux_owner;
         const struct pinctrl_setting_mux *mux_setting;
+        const char *gpio_owner;
 #endif
 };
 
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 86e401754116..4e62783a573a 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -94,17 +94,28 @@ static int pin_request(struct pinctrl_dev *pctldev,
                 goto out;
         }
 
-        if (desc->usecount && strcmp(desc->owner, owner)) {
-                dev_err(pctldev->dev,
-                        "pin already requested\n");
-                goto out;
-        }
+        if (gpio_range) {
+                /* There's no need to support multiple GPIO requests */
+                if (desc->gpio_owner) {
+                        dev_err(pctldev->dev,
+                                "pin already requested\n");
+                        goto out;
+                }
 
-        desc->usecount++;
-        if (desc->usecount > 1)
-                return 0;
+                desc->gpio_owner = owner;
+        } else {
+                if (desc->mux_usecount && strcmp(desc->mux_owner, owner)) {
+                        dev_err(pctldev->dev,
+                                "pin already requested\n");
+                        goto out;
+                }
 
-        desc->owner = owner;
+                desc->mux_usecount++;
+                if (desc->mux_usecount > 1)
+                        return 0;
+
+                desc->mux_owner = owner;
+        }
 
         /* Let each pin increase references to this module */
         if (!try_module_get(pctldev->owner)) {
@@ -135,9 +146,13 @@ static int pin_request(struct pinctrl_dev *pctldev,
 
 out_free_pin:
         if (status) {
-                desc->usecount--;
-                if (!desc->usecount)
-                        desc->owner = NULL;
+                if (gpio_range) {
+                        desc->gpio_owner = NULL;
+                } else {
+                        desc->mux_usecount--;
+                        if (!desc->mux_usecount)
+                                desc->mux_owner = NULL;
+                }
         }
 out:
         if (status)
@@ -172,9 +187,11 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin,
                 return NULL;
         }
 
-        desc->usecount--;
-        if (desc->usecount)
-                return NULL;
+        if (!gpio_range) {
+                desc->mux_usecount--;
+                if (desc->mux_usecount)
+                        return NULL;
+        }
 
         /*
          * If there is no kind of request function for the pin we just assume
@@ -185,9 +202,15 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin,
         else if (ops->free)
                 ops->free(pctldev, pin);
 
-        owner = desc->owner;
-        desc->owner = NULL;
-        desc->mux_setting = NULL;
+        if (gpio_range) {
+                owner = desc->gpio_owner;
+                desc->gpio_owner = NULL;
+        } else {
+                owner = desc->mux_owner;
+                desc->mux_owner = NULL;
+                desc->mux_setting = NULL;
+        }
+
         module_put(pctldev->owner);
 
         return owner;
@@ -493,7 +516,7 @@ static int pinmux_pins_show(struct seq_file *s, void *what)
         unsigned i, pin;
 
         seq_puts(s, "Pinmux settings per pin\n");
-        seq_puts(s, "Format: pin (name): owner\n");
+        seq_puts(s, "Format: pin (name): mux_owner gpio_owner hog?\n");
 
         mutex_lock(&pinctrl_mutex);
 
@@ -508,13 +531,16 @@ static int pinmux_pins_show(struct seq_file *s, void *what)
                 if (desc == NULL)
                         continue;
 
-                if (desc->owner &&
-                    !strcmp(desc->owner, pinctrl_dev_get_name(pctldev)))
+                if (desc->mux_owner &&
+                    !strcmp(desc->mux_owner, pinctrl_dev_get_name(pctldev)))
                         is_hog = true;
 
-                seq_printf(s, "pin %d (%s): %s%s", pin,
+                seq_printf(s, "pin %d (%s): %s %s%s", pin,
                            desc->name ? desc->name : "unnamed",
-                           desc->owner ? desc->owner : "UNCLAIMED",
+                           desc->mux_owner ? desc->mux_owner
+                                : "(MUX UNCLAIMED)",
+                           desc->gpio_owner ? desc->gpio_owner
+                                : "(GPIO UNCLAIMED)",
                            is_hog ? " (HOG)" : "");
 
                 if (desc->mux_setting)