Re: [RFC 0/7] Add PWM device-tree support.

[Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 12/20/2011 04:32 AM, Thierry Reding wrote:
> This patch series adds very rudimentary device-tree support for PWM devices.
> I fully realize that this is early work and it should not be merged as is.
> However I wanted to post these patches for review to make sure I'm not on a
> wild-goose chase.
> 
> With all of these patches applied (plus one board-specific patch that is not
> included), I'm able to control the backlight on the device I'm working on
> using the sysfs interface provided by the pwm-backlight driver and the
> backlight class.
> 
> This series is based on Sascha Hauer's series of patches[0] to add a generic
> PWM framework. The first patch in this series is takes from Sascha's branch,
> while the second patch enables each PWM chip to provide multiple PWM devices
> (none of the drivers in Sascha's branch are converted yet).
> 
> Patch 3 adds some code to lookup a PWM chip given its device-tree handle. This
> code will be used later on by the pwm-backlight driver to find the PWM device
> that it should be using. I did not include any binding documentation yet since
> I wasn't sure the DT binding was at all sensible.
> 
> Patch 4 was taken from the Chromium tree and is required to provide proper
> clocking of the Tegra2 PWFM controller. All Chromium-specific tags have been
> removed from the commit message.
> 
> Patch 5 cleans up the clock registration for Tegra2 because patch 6 will only
> instantiate one device for the PWFM controller instead of four.
> 
> Patch 6 adds a generic PWM framework driver for the Tegra2 PWFM controller.
> The code is taken from the Chromium tree with some adjustments to integrate it
> with the PWM framework.
> 
> Patch 7 implements DT-based probing in the pwm-backlight driver. Note that
> this code only handles the "pwm" property (by looking up the PWM device via
> the new PWM DT binding) and the "default-" and "max-brightness" properties.
> Switching power to the backlight via GPIOs is not supported yet.
> 
> [0]: http://git.pengutronix.de/?p=imx/linux-2.6.git;a=shortlog;h=refs/heads/pwmlib
> 
> Sascha Hauer (1):
>   PWM: add pwm framework support
> 
> Simon Que (1):
>   arm: tegra: Fix PWM clock programming
> 
> Thierry Reding (5):
>   pwm: Allow chips to support multiple PWMs.
>   of: Add PWM support.
>   arm: tegra: Provide clock for only one PWM controller.
>   pwm: Add Tegra2 SoC support
>   pwm-backlight: Add rudimentary device-tree support
> 
>  .../bindings/video/backlight/pwm-backlight         |   16 +
>  Documentation/pwm.txt                              |   56 ++++
>  MAINTAINERS                                        |    6 +
>  arch/arm/boot/dts/tegra20.dtsi                     |    6 +
>  arch/arm/mach-tegra/board-dt.c                     |    1 +
>  arch/arm/mach-tegra/clock.h                        |    1 +
>  arch/arm/mach-tegra/devices.c                      |   15 +
>  arch/arm/mach-tegra/devices.h                      |    1 +
>  arch/arm/mach-tegra/tegra2_clocks.c                |   33 ++-
>  drivers/Kconfig                                    |    2 +
>  drivers/Makefile                                   |    1 +
>  drivers/of/Kconfig                                 |    6 +
>  drivers/of/Makefile                                |    1 +
>  drivers/of/pwm.c                                   |   88 ++++++
>  drivers/pwm/Kconfig                                |   17 ++
>  drivers/pwm/Makefile                               |    2 +
>  drivers/pwm/core.c                                 |  301 ++++++++++++++++++++
>  drivers/pwm/pwm-tegra.c                            |  274 ++++++++++++++++++
>  drivers/video/backlight/Kconfig                    |    2 +-
>  drivers/video/backlight/pwm_bl.c                   |   70 +++++-
>  include/linux/of_pwm.h                             |   41 +++
>  include/linux/pwm.h                                |   49 ++++
>  22 files changed, 976 insertions(+), 13 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/video/backlight/pwm-backlight
>  create mode 100644 Documentation/pwm.txt
>  create mode 100644 drivers/of/pwm.c
>  create mode 100644 drivers/pwm/Kconfig
>  create mode 100644 drivers/pwm/Makefile
>  create mode 100644 drivers/pwm/core.c
>  create mode 100644 drivers/pwm/pwm-tegra.c
>  create mode 100644 include/linux/of_pwm.h

You need binding documentation for the pwm portion.

Rob