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 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);
--
2.19.2
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