Merge branch 'for-3.6' of git://gitorious.org/linux-pwm/linux-pwm

Pull PWM subsystem from Thierry Reding:
 "The new PWM subsystem aims at collecting all implementations of the
  legacy PWM API and to eventually replace it completely.

  The subsystem has been in development for over half a year now and
  many drivers have already been converted.  It has been in linux-next
  for a couple of weeks and there have been no major issues so I think
  it is ready for inclusion in your tree."

Arnd Bergmann <arnd@arndb.de>:
 "Very much Ack on the new subsystem.  It uses the interface
  declarations as the previously separate pwm drivers, so nothing
  changes for now in the drivers using it, although it enables us to
  change those more easily in the future if we want to.

  This work is also one of the missing pieces that are required to
  eventually build ARM kernels for multiple platforms, which is
  currently prohibited (amongs other things) by the fact that you cannot
  have more than one driver exporting the pwm functions."

Tested-and-acked-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Philip, Avinash <avinashphilip@ti.com> # TI's AM33xx platforms
Acked-By: Alexandre Pereira da Silva <aletes.xgr@gmail.com> # LPC32XX
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sachin Kamat <sachin.kamat@linaro.org>

Fix up trivial conflicts with other cleanups and DT updates.

* 'for-3.6' of git://gitorious.org/linux-pwm/linux-pwm: (36 commits)
  pwm: pwm-tiehrpwm: PWM driver support for EHRPWM
  pwm: pwm-tiecap: PWM driver support for ECAP APWM
  pwm: fix used-uninitialized warning in pwm_get()
  pwm: add lpc32xx PWM support
  pwm_backlight: pass correct brightness to callback
  pwm: Use pr_* functions in pwm-samsung.c file
  pwm: Convert pwm-samsung to use devm_* APIs
  pwm: Convert pwm-tegra to use devm_clk_get()
  pwm: pwm-mxs: Return proper error if pwmchip_remove() fails
  pwm: pwm-bfin: Return proper error if pwmchip_remove() fails
  pwm: pxa: Propagate pwmchip_remove() error
  pwm: Convert pwm-pxa to use devm_* APIs
  pwm: Convert pwm-vt8500 to use devm_* APIs
  pwm: Convert pwm-imx to use devm_* APIs
  pwm: Conflict with legacy PWM API
  pwm: pwm-mxs: add pinctrl support
  pwm: pwm-mxs: use devm_* managed functions
  pwm: pwm-mxs: use global reset function stmp_reset_block
  pwm: pwm-mxs: encode soc name in compatible string
  pwm: Take over maintainership of the PWM subsystem
  ...

1 files changed, 76 insertions, 0 deletions

diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
new file mode 100644
index 00000000000..554290ebab9
--- /dev/null
+++ b/Documentation/pwm.txt
@@ -0,0 +1,76 @@
+Pulse Width Modulation (PWM) interface
+
+This provides an overview about the Linux PWM interface
+
+PWMs are commonly used for controlling LEDs, fans or vibrators in
+cell phones. PWMs with a fixed purpose have no need implementing
+the Linux PWM API (although they could). However, PWMs are often
+found as discrete devices on SoCs which have no fixed purpose. It's
+up to the board designer to connect them to LEDs or fans. To provide
+this kind of flexibility the generic PWM API exists.
+
+Identifying PWMs
+----------------
+
+Users of the legacy PWM API use unique IDs to refer to PWM devices.
+
+Instead of referring to a PWM device via its unique ID, board setup code
+should instead register a static mapping that can be used to match PWM
+consumers to providers, as given in the following example:
+
+	static struct pwm_lookup board_pwm_lookup[] = {
+		PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL),
+	};
+
+	static void __init board_init(void)
+	{
+		...
+		pwm_add_table(board_pwm_lookup, ARRAY_SIZE(board_pwm_lookup));
+		...
+	}
+
+Using PWMs
+----------
+
+Legacy users can request a PWM device using pwm_request() and free it
+after usage with pwm_free().
+
+New users should use the pwm_get() function and pass to it the consumer
+device or a consumer name. pwm_put() is used to free the PWM device.
+
+After being requested a PWM has to be configured using:
+
+int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
+
+To start/stop toggling the PWM output use pwm_enable()/pwm_disable().
+
+Implementing a PWM driver
+-------------------------
+
+Currently there are two ways to implement pwm drivers. Traditionally
+there only has been the barebone API meaning that each driver has
+to implement the pwm_*() functions itself. This means that it's impossible
+to have multiple PWM drivers in the system. For this reason it's mandatory
+for new drivers to use the generic PWM framework.
+
+A new PWM controller/chip can be added using pwmchip_add() and removed
+again with pwmchip_remove(). pwmchip_add() takes a filled in struct
+pwm_chip as argument which provides a description of the PWM chip, the
+number of PWM devices provider by the chip and the chip-specific
+implementation of the supported PWM operations to the framework.
+
+Locking
+-------
+
+The PWM core list manipulations are protected by a mutex, so pwm_request()
+and pwm_free() may not be called from an atomic context. Currently the
+PWM core does not enforce any locking to pwm_enable(), pwm_disable() and
+pwm_config(), so the calling context is currently driver specific. This
+is an issue derived from the former barebone API and should be fixed soon.
+
+Helpers
+-------
+
+Currently a PWM can only be configured with period_ns and duty_ns. For several
+use cases freq_hz and duty_percent might be better. Instead of calculating
+this in your driver please consider adding appropriate helpers to the framework.