pwm: Read initial hardware state at request time

Drivers that support reading the hardware state (using ->get_state())
may want to rely on per-PWM data to do so. Defer reading the hardware
state for the first time until the PWM has been requested and after
drivers have had a chance to allocate per-PWM data.

Conceptually this is also a more natural place to read the hardware
state because the PWM core doesn't need to know the hardware state of a
PWM unless there is a user for it. This also ensures that the state is
read everytime a user requests a PWM. If the PWM changes between users
for some reason, the PWM core will reload the state from hardware and
keep its copy of the state up-to-date.
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Michal Vokáč <michal.vokac@ysoft.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/core.c

@@ -114,6 +114,9 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
 		}
 	}
 
+	if (pwm->chip->ops->get_state)
+		pwm->chip->ops->get_state(pwm->chip, pwm, &pwm->state);
+
 	set_bit(PWMF_REQUESTED, &pwm->flags);
 	pwm->label = label;
 
@@ -283,9 +286,6 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
 		pwm->hwpwm = i;
 		pwm->state.polarity = polarity;
 
-		if (chip->ops->get_state)
-			chip->ops->get_state(chip, pwm, &pwm->state);
-
 		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
 	}