pwm-backlight: Track enable state

Follow up patches will add support for more complex means of powering
the backlight on and off such as using a regulator. To prevent calls to
the regulator API from becoming unbalanced, keep track of the enabled
state internally.

Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index ab9d5e6012a4..4053efbe5edb 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -27,6 +27,7 @@ struct pwm_bl_data {
         unsigned int            period;
         unsigned int            lth_brightness;
         unsigned int            *levels;
+        bool                    enabled;
         int                     (*notify)(struct device *,
                                           int brightness);
         void                    (*notify_after)(struct device *,
@@ -40,6 +41,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness,
 {
         int duty_cycle, err;
 
+        if (pb->enabled)
+                return;
+
         if (pb->levels) {
                 duty_cycle = pb->levels[brightness];
                 max = pb->levels[max];
@@ -52,12 +56,18 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness,
 
         pwm_config(pb->pwm, duty_cycle, pb->period);
         pwm_enable(pb->pwm);
+        pb->enabled = true;
 }
 
 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 {
+        if (!pb->enabled)
+                return;
+
         pwm_config(pb->pwm, 0, pb->period);
         pwm_disable(pb->pwm);
+
+        pb->enabled = false;
 }
 
 static int pwm_backlight_update_status(struct backlight_device *bl)
@@ -216,6 +226,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
         pb->check_fb = data->check_fb;
         pb->exit = data->exit;
         pb->dev = &pdev->dev;
+        pb->enabled = false;
 
         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
         if (IS_ERR(pb->pwm)) {