Commit cfc4c189 authored Oct 21, 2019 by Thierry Reding

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>

parent e42617b8

drivers/pwm/core.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -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);
		}

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