drivers: create a pin control subsystem

This creates a subsystem for handling of pin control devices.
These are devices that control different aspects of package
pins.

Currently it handles pinmuxing, i.e. assigning electronic
functions to groups of pins on primarily PGA and BGA type of
chip packages which are common in embedded systems.

The plan is to also handle other I/O pin control aspects
such as biasing, driving, input properties such as
schmitt-triggering, load capacitance etc within this
subsystem, to remove a lot of ARM arch code as well as
feature-creepy GPIO drivers which are implementing the same
thing over and over again.

This is being done to depopulate the arch/arm/* directory
of such custom drivers and try to abstract the infrastructure
they all need. See the Documentation/pinctrl.txt file that is
part of this patch for more details.

ChangeLog v1->v2:

- Various minor fixes from Joe's and Stephens review comments
- Added a pinmux_config() that can invoke custom configuration
  with arbitrary data passed in or out to/from the pinmux driver

ChangeLog v2->v3:

- Renamed subsystem folder to "pinctrl" since we will likely
  want to keep other pin control such as biasing in this
  subsystem too, so let us keep to something generic even though
  we're mainly doing pinmux now.
- As a consequence, register pins as an abstract entity separate
  from the pinmux. The muxing functions will claim pins out of the
  pin pool and make sure they do not collide. Pins can now be
  named by the pinctrl core.
- Converted the pin lookup from a static array into a radix tree,
  I agreed with Grant Likely to try to avoid any static allocation
  (which is crap for device tree stuff) so I just rewrote this
  to be dynamic, just like irq number descriptors. The
  platform-wide definition of number of pins goes away - this is
  now just the sum total of the pins registered to the subsystem.
- Make sure mappings with only a function name and no device
  works properly.

ChangeLog v3->v4:

- Define a number space per controller instead of globally,
  Stephen and Grant requested the same thing so now maps need to
  define target controller, and the radix tree of pin descriptors
  is a property on each pin controller device.
- Add a compulsory pinctrl device entry to the pinctrl mapping
  table. This must match the pinctrl device, like "pinctrl.0"
- Split the file core.c in two: core.c and pinmux.c where the
  latter carry all pinmux stuff, the core is for generic pin
  control, and use local headers to access functionality between
  files. It is now possible to implement a "blank" pin controller
  without pinmux capabilities. This split will make new additions
  like pindrive.c, pinbias.c etc possible for combined drivers
  and chunks of functionality which is a GoodThing(TM).
- Rewrite the interaction with the GPIO subsystem - the pin
  controller descriptor now handles this by defining an offset
  into the GPIO numberspace for its handled pin range. This is
  used to look up the apropriate pin controller for a GPIO pin.
  Then that specific GPIO range is matched 1-1 for the target
  controller instance.
- Fixed a number of review comments from Joe Perches.
- Broke out a header file pinctrl.h for the core pin handling
  stuff that will be reused by other stuff than pinmux.
- Fixed some erroneous EXPORT() stuff.
- Remove mispatched U300 Kconfig and Makefile entries
- Fixed a number of review comments from Stephen Warren, not all
  of them - still WIP. But I think the new mapping that will
  specify which function goes to which pin mux controller address
  50% of your concerns (else beat me up).

ChangeLog v4->v5:

- Defined a "position" for each function, so the pin controller now
  tracks a function in a certain position, and the pinmux maps define
  what position you want the function in. (Feedback from Stephen
  Warren and Sascha Hauer).
- Since we now need to request a combined function+position from
  the machine mapping table that connect mux settings to drivers,
  it was extended with a position field and a name field. The
  name field is now used if you e.g. need to switch between two
  mux map settings at runtime.
- Switched from a class device to using struct bus_type for this
  subsystem. Verified sysfs functionality: seems to work fine.
  (Feedback from Arnd Bergmann and Greg Kroah-Hartman)
- Define a per pincontroller list of GPIO ranges from the GPIO
  pin space that can be handled by the pin controller. These can
  be added one by one at runtime. (Feedback from Barry Song)
- Expanded documentation of regulator_[get|enable|disable|put]
  semantics.
- Fixed a number of review comments from Barry Song. (Thanks!)

ChangeLog v5->v6:

- Create an abstract pin group concept that can sort pins into
  named and enumerated groups no matter what the use of these
  groups may be, one possible usecase is a group of pins being
  muxed in or so. The intention is however to also use these
  groups for other pin control activities.
- Make it compulsory for pinmux functions to associate with
  at least one group, so the abstract pin group concept is used
  to define the groups of pins affected by a pinmux function.
  The pinmux driver interface has been altered so as to enforce
  a function to list applicable groups per function.
- Provide an optional .group entry in the pinmux machine map
  so the map can select beteween different available groups
  to be used with a certain function.
- Consequent changes all over the place so that e.g. debugfs
  present reasonable information about the world.
- Drop the per-pin mux (*config) function in the pinmux_ops
  struct - I was afraid that this would start to be used for
  things totally unrelated to muxing, we can introduce that to
  the generic struct pinctrl_ops if needed. I want to keep
  muxing orthogonal to other pin control subjects and not mix
  these things up.

ChangeLog v6->v7:

- Make it possible to have several map entries matching the
  same device, pin controller and function, but using
  a different group, and alter the semantics so that
  pinmux_get() will pick all matching map entries, and
  store the associated groups in a list. The list will
  then be iterated over at pinmux_enable()/pinmux_disable()
  and corresponding driver functions called for each
  defined group. Notice that you're only allowed to map
  multiple *groups* to the same
  { device, pin controller, function } triplet, attempts
  to map the same device to multiple pin controllers will
  for example fail. This is hopefully the crucial feature
  requested by Stephen Warren.
- Add a pinmux hogging field to the pinmux mapping entries,
  and enable the pinmux core to hog pinmux map entries.
  This currently only works for pinmuxes without assigned
  devices as it looks now, but with device trees we can
  look up the corresponding struct device * entries when
  we register the pinmux driver, and have it hog each
  pinmux map in turn, for a simple approach to
  non-dynamic pin muxing. This addresses an issue from
  Grant Likely that the machine should take care of as
  much of the pinmux setup as possible, not the devices.
  By supplying a list of hogs, it can now instruct the
  core to take care of any static mappings.
- Switch pinmux group retrieveal function to grab an
  array of strings representing the groups rather than an
  array of unsigned and rewrite accordingly.
- Alter debugfs to show the grouplist handled by each
  pinmux. Also add a list of hogs.
- Dynamically allocate a struct pinmux at pinmux_get() and
  free it at pinmux_put(), then add these to the global
  list of pinmuxes active as we go along.
- Go over the list of pinmux maps at pinmux_get() time
  and repeatedly apply matches.
- Retrieve applicable groups per function from the driver
  as a string array rather than a unsigned array, then
  lookup the enumerators.
- Make the device to pinmux map a singleton - only allow the
  mapping table to be registered once and even tag the
  registration function with __init so it surely won't be
  abused.
- Create a separate debugfs file to view the pinmux map at
  runtime.
- Introduce a spin lock to the pin descriptor struct, lock it
  when modifying pin status entries. Reported by Stijn Devriendt.
- Fix up the documentation after review from Stephen Warren.
- Let the GPIO ranges give names as const char * instead of some
  fixed-length string.
- add a function to unregister GPIO ranges to mirror the
  registration function.
- Privatized the struct pinctrl_device and removed it from the
  <linux/pinctrl/pinctrl.h> API, the drivers do not need to know
  the members of this struct. It is now in the local header
  "core.h".
- Rename the concept of "anonymous" mux maps to "system" muxes
  and add convenience macros and documentation.

ChangeLog v7->v8:

- Delete the leftover pinmux_config() function from the
 <linux/pinctrl/pinmux.h> header.
- Fix a race condition found by Stijn Devriendt in pin_request()

ChangeLog v8->v9:

- Drop the bus_type and the sysfs attributes and all, we're not on
  the clear about how this should be used for e.g. userspace
  interfaces so let us save this for the future.
- Use the right name in MAINTAINERS, PIN CONTROL rather than
  PINMUX
- Don't kfree() the device state holder, let the .remove() callback
  handle this.
- Fix up numerous kerneldoc headers to have one line for the function
  description and more verbose documentation below the parameters

ChangeLog v9->v10:
- pinctrl: EXPORT_SYMBOL needs export.h, folded in a patch
  from Steven Rothwell
- fix pinctrl_register error handling, folded in a patch from
  Axel Lin
- Various fixes to documentation text so that it's consistent.
- Removed pointless comment from drivers/Kconfig
- Removed dependency on SYSFS since we removed the bus in
  v9.
- Renamed hopelessly abbreviated pctldev_* functions to the
  more verbose pinctrl_dev_*
- Drop mutex properly when looking up GPIO ranges
- Return NULL instead of ERR_PTR() errors on registration of
  pin controllers, using cast pointers is fragile. We can
  live without the detailed error codes for sure.

Cc: Stijn Devriendt <highguy@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Barry Song <21cnbao@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 117 insertions, 0 deletions

diff --git a/include/linux/pinctrl/pinmux.h b/include/linux/pinctrl/pinmux.h
new file mode 100644
index 000000000000..3c430e797efc
--- /dev/null
+++ b/include/linux/pinctrl/pinmux.h
@@ -0,0 +1,117 @@
+/*
+ * Interface the pinmux subsystem
+ *
+ * Copyright (C) 2011 ST-Ericsson SA
+ * Written on behalf of Linaro for ST-Ericsson
+ * Based on bits of regulator core, gpio core and clk core
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ *
+ * License terms: GNU General Public License (GPL) version 2
+ */
+#ifndef __LINUX_PINCTRL_PINMUX_H
+#define __LINUX_PINCTRL_PINMUX_H
+
+#include <linux/list.h>
+#include <linux/seq_file.h>
+#include "pinctrl.h"
+
+/* This struct is private to the core and should be regarded as a cookie */
+struct pinmux;
+
+#ifdef CONFIG_PINMUX
+
+struct pinctrl_dev;
+
+/**
+ * struct pinmux_ops - pinmux operations, to be implemented by pin controller
+ * drivers that support pinmuxing
+ * @request: called by the core to see if a certain pin can be made available
+ *	available for muxing. This is called by the core to acquire the pins
+ *	before selecting any actual mux setting across a function. The driver
+ *	is allowed to answer "no" by returning a negative error code
+ * @free: the reverse function of the request() callback, frees a pin after
+ *	being requested
+ * @list_functions: list the number of selectable named functions available
+ *	in this pinmux driver, the core will begin on 0 and call this
+ *	repeatedly as long as it returns >= 0 to enumerate mux settings
+ * @get_function_name: return the function name of the muxing selector,
+ *	called by the core to figure out which mux setting it shall map a
+ *	certain device to
+ * @get_function_groups: return an array of groups names (in turn
+ *	referencing pins) connected to a certain function selector. The group
+ *	name can be used with the generic @pinctrl_ops to retrieve the
+ *	actual pins affected. The applicable groups will be returned in
+ *	@groups and the number of groups in @num_groups
+ * @enable: enable a certain muxing function with a certain pin group. The
+ *	driver does not need to figure out whether enabling this function
+ *	conflicts some other use of the pins in that group, such collisions
+ *	are handled by the pinmux subsystem. The @func_selector selects a
+ *	certain function whereas @group_selector selects a certain set of pins
+ *	to be used. On simple controllers the latter argument may be ignored
+ * @disable: disable a certain muxing selector with a certain pin group
+ * @gpio_request_enable: requests and enables GPIO on a certain pin.
+ *	Implement this only if you can mux every pin individually as GPIO. The
+ *	affected GPIO range is passed along with an offset into that
+ *	specific GPIO range - function selectors and pin groups are orthogonal
+ *	to this, the core will however make sure the pins do not collide
+ */
+struct pinmux_ops {
+	int (*request) (struct pinctrl_dev *pctldev, unsigned offset);
+	int (*free) (struct pinctrl_dev *pctldev, unsigned offset);
+	int (*list_functions) (struct pinctrl_dev *pctldev, unsigned selector);
+	const char *(*get_function_name) (struct pinctrl_dev *pctldev,
+					  unsigned selector);
+	int (*get_function_groups) (struct pinctrl_dev *pctldev,
+				  unsigned selector,
+				  const char * const **groups,
+				  unsigned * const num_groups);
+	int (*enable) (struct pinctrl_dev *pctldev, unsigned func_selector,
+		       unsigned group_selector);
+	void (*disable) (struct pinctrl_dev *pctldev, unsigned func_selector,
+			 unsigned group_selector);
+	int (*gpio_request_enable) (struct pinctrl_dev *pctldev,
+				    struct pinctrl_gpio_range *range,
+				    unsigned offset);
+};
+
+/* External interface to pinmux */
+extern int pinmux_request_gpio(unsigned gpio);
+extern void pinmux_free_gpio(unsigned gpio);
+extern struct pinmux * __must_check pinmux_get(struct device *dev, const char *name);
+extern void pinmux_put(struct pinmux *pmx);
+extern int pinmux_enable(struct pinmux *pmx);
+extern void pinmux_disable(struct pinmux *pmx);
+
+#else /* !CONFIG_PINMUX */
+
+static inline int pinmux_request_gpio(unsigned gpio)
+{
+	return 0;
+}
+
+static inline void pinmux_free_gpio(unsigned gpio)
+{
+}
+
+static inline struct pinmux * __must_check pinmux_get(struct device *dev, const char *name)
+{
+	return NULL;
+}
+
+static inline void pinmux_put(struct pinmux *pmx)
+{
+}
+
+static inline int pinmux_enable(struct pinmux *pmx)
+{
+	return 0;
+}
+
+static inline void pinmux_disable(struct pinmux *pmx)
+{
+}
+
+#endif /* CONFIG_PINMUX */
+
+#endif /* __LINUX_PINCTRL_PINMUX_H */