backlight: pwm_bl: Fix brightness levels for non-DT case.

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")
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>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 678b270631983a47718d5d8d78f395e9d639ec83..f9ef0673a083cb63c776ca58631710e659329ee3 100644 (file)
--- 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);