Hi,
Missatge de Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx> del
dia dc., 7 de nov. 2018 a les 9:56:
>
> 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@xxxxxxxxxxxxxxx>
> Reported-by: Robert Jarzmik <robert.jarzmik@xxxxxxx>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> Tested-by: Robert Jarzmik <robert.jarzmik@xxxxxxx>
> Acked-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
> ---
>
> 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 678b27063198..f9ef0673a083 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -562,7 +562,30 @@ 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) {
> @@ -570,13 +593,19 @@ 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);
> --
> 2.19.1
>
A gentle ping on this patch.
Best regards,
Enric
