pwm: rockchip: State of PWM clock should synchronize with PWM enabled state

pwm: rockchip: State of PWM clock should synchronize with PWM enabled state

commit a900152b5c29aea8134cc7a4c5db25552b3cd8f7 upstream.

If the PWM was not enabled at U-Boot loader, PWM could not work for
clock always disabled at PWM driver. The PWM clock is enabled at
beginning of pwm_apply(), but disabled at end of pwm_apply().

If the PWM was enabled at U-Boot loader, PWM clock is always enabled
unless closed by ATF. The pwm-backlight might turn off the power at
early suspend, should disable PWM clock for saving power consume.

It is important to provide opportunity to enable/disable clock at PWM
driver, the PWM consumer should ensure correct order to call PWM enable
and disable, and PWM driver ensure state of PWM clock synchronized with
PWM enabled state.

Fixes: 2bf1c98aa5a4 ("pwm: rockchip: Add support for atomic update")
Signed-off-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>