Armada 370/XP devices can 'blink' GPIO lines with a configurable on
and off period. This can be modelled as a PWM.

However, there are only two sets of PWM configuration registers for
all the GPIO lines. This driver simply allows a single GPIO line per
GPIO chip of 32 lines to be used as a PWM. Attempts to use more return
EBUSY.

Due to the interleaving of registers it is not simple to separate the
PWM driver from the GPIO driver. Thus the GPIO driver has been
extended with a PWM driver.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
URL: https://patchwork.ozlabs.org/patch/427287/
URL: https://patchwork.ozlabs.org/patch/427295/
[Ralph Sennhauser:
  * Port forward
  * Merge PWM portion into gpio-mvebu.c
  * Switch to atomic PWM API
  * Add new compatible string marvell,armada-370-xp-gpio
  * Update and merge documentation patch
  * Update MAINTAINERS]
Signed-off-by: NRalph Sennhauser <ralph.sennhauser@gmail.com>
Tested-by: NAndrew Lunn <andrew@lunn.ch>
Acked-by: NThierry Reding <thierry.reding@gmail.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>