On Tue, Jun 07, 2016 at 12:13:49PM +0200, Lothar Waßmann wrote:

'brightness' is usually an index into a table of duty_cycle values,
where the value at index 0 may well be non-zero
(tegra30-apalis-eval.dts and tegra30-colibri-eval-v3.dts are real-life
examples).
Thus brightness == 0 does not necessarily mean that the PWM output
will be inactive.
Check for 'duty_cycle == 0' rather than 'brightness == 0' to decide
whether to disable the PWM.

Signed-off-by: Lothar Waßmann <redacted>
---
Changes wrt. v1:
  - update binding docs to reflect the change

 .../devicetree/bindings/leds/backlight/pwm-backlight.txt         | 9 ++++++---
 drivers/video/backlight/pwm_bl.c                                 | 4 ++--
 2 files changed, 8 insertions(+), 5 deletions(-)

Acked-by: Rob Herring <robh@kernel.org>