regulator: pwm-regulator: Add validity checks in continuous .get_voltage

Continuous regulators can be configured to operate only in a certain
duty cycle range (for example from 0..91%). Add a check to error out if
the duty cycle translates to an unsupported (or out of range) voltage.
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://msgid.link/r/20240113224628.377993-2-martin.blumenstingl@googlemail.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/pwm-regulator.c

@@ -158,6 +158,9 @@ static int pwm_regulator_get_voltage(struct regulator_dev *rdev)
 	pwm_get_state(drvdata->pwm, &pstate);
 
 	voltage = pwm_get_relative_duty_cycle(&pstate, duty_unit);
+	if (voltage < min(max_uV_duty, min_uV_duty) ||
+	    voltage > max(max_uV_duty, min_uV_duty))
+		return -ENOTRECOVERABLE;
 
 	/*
 	 * The dutycycle for min_uV might be greater than the one for max_uV.