pinctrl: add a pin config interface

This add per-pin and per-group pin config interfaces for biasing,
driving and other such electronic properties. The details of passed
configurations are passed in an opaque unsigned long which may be
dereferences to integer types, structs or lists on either side
of the configuration interface.

ChangeLog v1->v2:
- Clear split of terminology: we now have pin controllers, and
  those may support two interfaces using vtables: pin
  multiplexing and pin configuration.
- Break out pin configuration to its own C file, controllers may
  implement only config without mux, and vice versa, so keep each
  sub-functionality of pin controllers separate. Introduce
  CONFIG_PINCONF in Kconfig.
- Implement some core logic around pin configuration in the
  pinconf.c file.
- Remove UNKNOWN config states, these were just surplus baggage.
- Remove FLOAT config state - HIGH_IMPEDANCE should be enough for
  everyone.
- PIN_CONFIG_POWER_SOURCE added to handle switching the power
  supply for the pin logic between different sources
- Explicit DISABLE config enums to turn schmitt-trigger,
  wakeup etc OFF.
- Update documentation to reflect all the recent reasoning.
ChangeLog v2->v3:
- Twist API around to pass around arrays of config tuples instead
  of (param, value) pairs everywhere.
- Explicit drive strength semantics for push/pull and similar
  drive modes, this shall be the number of drive stages vs
  nominal load impedance, which should match the actual
  electronics used in push/pull CMOS or TTY totempoles.
- Drop load capacitance configuration - I probably don't know
  what I'm doing here so leave it out.
- Drop PIN_CONFIG_INPUT_SCHMITT_OFF, instead the argument zero to
  PIN_CONFIG_INPUT_SCHMITT turns schmitt trigger off.
- Drop PIN_CONFIG_NORMAL_POWER_MODE and have a well defined
  argument to PIN_CONFIG_LOW_POWER_MODE to get out of it instead.
- Drop PIN_CONFIG_WAKEUP_ENABLE/DISABLE and just use
  PIN_CONFIG_WAKEUP with defined value zero to turn wakeup off.
- Add PIN_CONFIG_INPUT_DEBOUNCE for configuring debounce time
  on input lines.
- Fix a bug when we tried to configure pins for pin controllers
  without pinconf support.
- Initialized debugfs properly so it works.
- Initialize the mutex properly and lock around config tampering
  sections.
- Check the return value from get_initial_config() properly.
ChangeLog v3->v4:
- Export the pin_config_get(), pin_config_set() and
  pin_config_group() functions.
- Drop the entire concept of just getting initial config and
  keeping track of pin states internally, instead ask the pins
  what state they are in. Previous idea was plain wrong, if the
  device cannot keep track of its state, the driver should do
  it.
- Drop the generic configuration layout, it seems this impose
  too much restriction on some pin controllers, so let them do
  things the way they want and split off support for generic
  config as an optional add-on.
ChangeLog v4->v5:
- Introduce two symmetric driver calls for group configuration,
  .pin_config_group_[get|set] and corresponding external calls.
- Remove generic semantic meanings of return values from config
  calls, these belong in the generic config patch. Just pass the
  return value through instead.
- Add a debugfs entry "pinconf-groups" to read status from group
  configuration only, also slam in a per-group debug callback in
  the pinconf_ops so custom drivers can display something
  meaningful for their pins.
- Fix some dangling newline.
- Drop dangling #else clause.
- Update documentation to match the above.
ChangeLog v5->v6:
- Change to using a pin name as parameter for the
  [get|set]_config() functions, as suggested by Stephen Warren.
  This is more natural as names will be what a developer has
  access to in written documentation etc.
ChangeLog v6->v7:
- Refactor out by-pin and by-name get/set functions, only expose
  the by-name functions externally, expose the by-pin functions
  internally.
- Show supported pin control functionality in the debugfs
  pinctrl-devices file.

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

2 files changed, 102 insertions, 2 deletions

diff --git a/include/linux/pinctrl/pinconf.h b/include/linux/pinctrl/pinconf.h
new file mode 100644
index 000000000000..d5b72e6e261d
--- /dev/null
+++ b/include/linux/pinctrl/pinconf.h
@@ -0,0 +1,96 @@
+/*
+ * Interface the pinconfig portions of the pinctrl subsystem
+ *
+ * Copyright (C) 2011 ST-Ericsson SA
+ * Written on behalf of Linaro for ST-Ericsson
+ * This interface is used in the core to keep track of pins.
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ *
+ * License terms: GNU General Public License (GPL) version 2
+ */
+#ifndef __LINUX_PINCTRL_PINCONF_H
+#define __LINUX_PINCTRL_PINCONF_H
+
+#ifdef CONFIG_PINCONF
+
+struct pinctrl_dev;
+
+/**
+ * struct pinconf_ops - pin config operations, to be implemented by
+ * pin configuration capable drivers.
+ * @pin_config_get: get the config of a certain pin, if the requested config
+ *      is not available on this controller this should return -ENOTSUPP
+ *      and if it is available but disabled it should return -EINVAL
+ * @pin_config_get: get the config of a certain pin
+ * @pin_config_set: configure an individual pin
+ * @pin_config_group_get: get configurations for an entire pin group
+ * @pin_config_group_set: configure all pins in a group
+ * @pin_config_dbg_show: optional debugfs display hook that will provide
+ *      per-device info for a certain pin in debugfs
+ * @pin_config_group_dbg_show: optional debugfs display hook that will provide
+ *      per-device info for a certain group in debugfs
+ */
+struct pinconf_ops {
+        int (*pin_config_get) (struct pinctrl_dev *pctldev,
+                               unsigned pin,
+                               unsigned long *config);
+        int (*pin_config_set) (struct pinctrl_dev *pctldev,
+                               unsigned pin,
+                               unsigned long config);
+        int (*pin_config_group_get) (struct pinctrl_dev *pctldev,
+                                     unsigned selector,
+                                     unsigned long *config);
+        int (*pin_config_group_set) (struct pinctrl_dev *pctldev,
+                                     unsigned selector,
+                                     unsigned long config);
+        void (*pin_config_dbg_show) (struct pinctrl_dev *pctldev,
+                                     struct seq_file *s,
+                                     unsigned offset);
+        void (*pin_config_group_dbg_show) (struct pinctrl_dev *pctldev,
+                                           struct seq_file *s,
+                                           unsigned selector);
+};
+
+extern int pin_config_get(struct pinctrl_dev *pctldev, const char *name,
+                          unsigned long *config);
+extern int pin_config_set(struct pinctrl_dev *pctldev, const char *name,
+                          unsigned long config);
+extern int pin_config_group_get(struct pinctrl_dev *pctldev,
+                                const char *pin_group,
+                                unsigned long *config);
+extern int pin_config_group_set(struct pinctrl_dev *pctldev,
+                                const char *pin_group,
+                                unsigned long config);
+
+#else
+
+static inline int pin_config_get(struct pinctrl_dev *pctldev, const char *name,
+                                 unsigned long *config)
+{
+        return 0;
+}
+
+static inline int pin_config_set(struct pinctrl_dev *pctldev, const char *name,
+                                 unsigned long config)
+{
+        return 0;
+}
+
+static inline int pin_config_group_get(struct pinctrl_dev *pctldev,
+                                       const char *pin_group,
+                                       unsigned long *config)
+{
+        return 0;
+}
+
+static inline int pin_config_group_set(struct pinctrl_dev *pctldev,
+                                       const char *pin_group,
+                                       unsigned long config)
+{
+        return 0;
+}
+
+#endif
+
+#endif /* __LINUX_PINCTRL_PINCONF_H */
diff --git a/include/linux/pinctrl/pinctrl.h b/include/linux/pinctrl/pinctrl.h
index f17fac4b51f1..9809a94f151b 100644
--- a/include/linux/pinctrl/pinctrl.h
+++ b/include/linux/pinctrl/pinctrl.h
@@ -21,6 +21,7 @@
 
 struct pinctrl_dev;
 struct pinmux_ops;
+struct pinconf_ops;
 struct gpio_chip;
 
 /**
@@ -97,7 +98,9 @@ struct pinctrl_ops {
  *      but may be equal to npins if you have no holes in the pin range.
  * @pctlops: pin control operation vtable, to support global concepts like
  *      grouping of pins, this is optional.
- * @pmxops: pinmux operation vtable, if you support pinmuxing in your driver
+ * @pmxops: pinmux operations vtable, if you support pinmuxing in your driver
+ * @confops: pin config operations vtable, if you support pin configuration in
+ *      your driver
  * @owner: module providing the pin controller, used for refcounting
  */
 struct pinctrl_desc {
@@ -107,6 +110,7 @@ struct pinctrl_desc {
         unsigned int maxpin;
         struct pinctrl_ops *pctlops;
         struct pinmux_ops *pmxops;
+        struct pinconf_ops *confops;
         struct module *owner;
 };
 
@@ -125,7 +129,7 @@ extern void *pinctrl_dev_get_drvdata(struct pinctrl_dev *pctldev);
 
 struct pinctrl_dev;
 
-/* Sufficiently stupid default function when pinctrl is not in use */
+/* Sufficiently stupid default functions when pinctrl is not in use */
 static inline bool pin_is_valid(struct pinctrl_dev *pctldev, int pin)
 {
         return pin >= 0;