backlight: pwm: Clean-up pwm requested using legacy API

If PWM device is requested by means of legacy API pwm_request(), its
resources are not freed on module unbind, which may cause an oops on
access, e.g. by reading /sys/kernel/debug/pwm.

Reported-by: Dmitry Eremin-Solenikov <dmitry_eremin@mentor.com>
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index cb5ae4c08469..3a145a643e0d 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -34,6 +34,7 @@ struct pwm_bl_data {
         struct regulator        *power_supply;
         struct gpio_desc        *enable_gpio;
         unsigned int            scale;
+        bool                    legacy;
         int                     (*notify)(struct device *,
                                           int brightness);
         void                    (*notify_after)(struct device *,
@@ -274,7 +275,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
         pb->pwm = devm_pwm_get(&pdev->dev, NULL);
         if (IS_ERR(pb->pwm)) {
                 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
-
+                pb->legacy = true;
                 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
                 if (IS_ERR(pb->pwm)) {
                         dev_err(&pdev->dev, "unable to request legacy PWM\n");
@@ -339,6 +340,8 @@ static int pwm_backlight_remove(struct platform_device *pdev)
 
         if (pb->exit)
                 pb->exit(&pdev->dev);
+        if (pb->legacy)
+                pwm_free(pb->pwm);
 
         return 0;
 }