misc: atmel_pwm: add deferred-probing support

Two drivers (atmel-pwm-bl and leds-atmel-pwm) currently depend on the
atmel_pwm driver to have bound to any pwm-device before their devices
are probed.

Support deferred probing of such devices by making sure to return
-EPROBE_DEFER from pwm_channel_alloc when no pwm-device has yet been
bound.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/misc/atmel_pwm.c b/drivers/misc/atmel_pwm.c
index 494d0500bda6..a6dc56e1bc58 100644
--- a/drivers/misc/atmel_pwm.c
+++ b/drivers/misc/atmel_pwm.c
@@ -90,8 +90,10 @@ int pwm_channel_alloc(int index, struct pwm_channel *ch)
         unsigned long   flags;
         int             status = 0;
 
-        /* insist on PWM init, with this signal pinned out */
-        if (!pwm || !(pwm->mask & 1 << index))
+        if (!pwm)
+                return -EPROBE_DEFER;
+
+        if (!(pwm->mask & 1 << index))
                 return -ENODEV;
 
         if (index < 0 || index >= PWM_NCHAN || !ch)