Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")' allows the possibility to compute a default brightness table when there isn't the brightness-levels property in the DT. Unfortunately the changes made broke the pwm backlight for the non-DT boards.

Usually, the non-DT boards don't pass the brightness levels via platform data, instead, it sets the max_brightness in their platform data and the driver calculates the level without a table. The offending patch assumed that when there is no brightness levels table we should create one, but this is clearly wrong for the non-DT case.

After this patch the code handles the DT and the non-DT case taking in consideration also if max_brightness is set or not.

Fixes: 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye") Cc: stable@vger.kernel.org Reported-by: Robert Jarzmik robert.jarzmik@free.fr Signed-off-by: Enric Balletbo i Serra enric.balletbo@collabora.com Tested-by: Robert Jarzmik robert.jarzmik@free.fr Acked-by: Daniel Thompson daniel.thompson@linaro.org ---

Changes in v3: - Fixed some typos in commit message. - Removed ' in Fixes tag.

Changes in v2: - Rebase on top of mainline - Add Tested-by and Acked-by tags.

drivers/video/backlight/pwm_bl.c | 41 +++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index b7b5b31f3824..feb90764a811 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -568,7 +568,30 @@ static int pwm_backlight_probe(struct platform_device *pdev) goto err_alloc; }

- if (!data->levels) { + if (data->levels) { + /* + * For the DT case, only when brightness levels is defined + * data->levels is filled. For the non-DT case, data->levels + * can come from platform data, however is not usual. + */ + for (i = 0; i <= data->max_brightness; i++) { + if (data->levels[i] > pb->scale) + pb->scale = data->levels[i]; + + pb->levels = data->levels; + } + } else if (!data->max_brightness) { + /* + * If no brightness levels are provided and max_brightness is + * not set, use the default brightness table. For the DT case, + * max_brightness is set to 0 when brightness levels is not + * specified. For the non-DT case, max_brightness is usually + * set to some value. + */ + + /* Get the PWM period (in nanoseconds) */ + pwm_get_state(pb->pwm, &state); + ret = pwm_backlight_brightness_default(&pdev->dev, data, state.period); if (ret < 0) { @@ -576,13 +599,19 @@ static int pwm_backlight_probe(struct platform_device *pdev) "failed to setup default brightness table\n"); goto err_alloc; } - }

- for (i = 0; i <= data->max_brightness; i++) { - if (data->levels[i] > pb->scale) - pb->scale = data->levels[i]; + for (i = 0; i <= data->max_brightness; i++) { + if (data->levels[i] > pb->scale) + pb->scale = data->levels[i];

- pb->levels = data->levels; + pb->levels = data->levels; + } + } else { + /* + * That only happens for the non-DT case, where platform data + * sets the max_brightness value. + */ + pb->scale = data->max_brightness; }

pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);