Platform PWM backlight data provided by board's device tree should be
complete enough to successfully request a pwm device using pwm_get()
API. This change fixes a bug, when an arbitrary (first found) PWM is
connected to a "pwm-backlight" compatible device, when explicit PWM
device reference is not given.

Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
already describes "pwms" as a required property, instead of blind
selection of a potentially wrong PWM reject legacy PWM device
registration request, leave legacy API only for non-dt cases.

Based on initial implementation done by Dmitry Eremin-Solenikov.

Reported-by: Dmitry Eremin-Solenikov <[email protected]>
Signed-off-by: Vladimir Zapolskiy <[email protected]>
Acked-by: Thierry Reding <[email protected]>
---
 drivers/video/backlight/pwm_bl.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 57cb9ec..9991cdb 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -271,15 +271,16 @@ static int pwm_backlight_probe(struct platform_device 
*pdev)
        }
 
        pb->pwm = devm_pwm_get(&pdev->dev, NULL);
-       if (IS_ERR(pb->pwm)) {
+       if (IS_ERR(pb->pwm) && !pdev->dev.of_node) {
                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");
-                       ret = PTR_ERR(pb->pwm);
-                       goto err_alloc;
-               }
+       }
+
+       if (IS_ERR(pb->pwm)) {
+               dev_err(&pdev->dev, "unable to request PWM\n");
+               ret = PTR_ERR(pb->pwm);
+               goto err_alloc;
        }
 
        dev_dbg(&pdev->dev, "got pwm for backlight\n");
-- 
2.1.4

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