pwm: vt8500: Implement .apply() callback

To eventually get rid of all legacy drivers convert this driver to the
modern world implementing .apply(). This just pushes down a slightly
optimized variant of how legacy drivers are handled in the core.

Signed-off-by: Uwe Kleine-König <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

drivers/pwm/pwm-vt8500.c

···
 }
 
 static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
-		int duty_ns, int period_ns)
+		u64 duty_ns, u64 period_ns)
 {
 	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
 	unsigned long long c;
···
 	}
 
 	c = (unsigned long long)pv * duty_ns;
-	do_div(c, period_ns);
-	dc = c;
+
+	dc = div64_u64(c, period_ns);
 
 	writel(prescale, vt8500->base + REG_SCALAR(pwm->hwpwm));
 	vt8500_pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_SCALAR_UPDATE);
···
 	return 0;
 }
 
+static int vt8500_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state)
+{
+	int err;
+	bool enabled = pwm->state.enabled;
+
+	if (state->polarity != pwm->state.polarity) {
+		/*
+		 * Changing the polarity of a running PWM is only allowed when
+		 * the PWM driver implements ->apply().
+		 */
+		if (enabled) {
+			vt8500_pwm_disable(chip, pwm);
+
+			enabled = false;
+		}
+
+		err = vt8500_pwm_set_polarity(chip, pwm, state->polarity);
+		if (err)
+			return err;
+	}
+
+	if (!state->enabled) {
+		if (enabled)
+			vt8500_pwm_disable(chip, pwm);
+
+		return 0;
+	}
+
+	/*
+	 * We cannot skip calling ->config even if state->period ==
+	 * pwm->state.period && state->duty_cycle == pwm->state.duty_cycle
+	 * because we might have exited early in the last call to
+	 * pwm_apply_state because of !state->enabled and so the two values in
+	 * pwm->state might not be configured in hardware.
+	 */
+	err = vt8500_pwm_config(pwm->chip, pwm, state->duty_cycle, state->period);
+	if (err)
+		return err;
+
+	if (!enabled)
+		err = vt8500_pwm_enable(chip, pwm);
+
+	return err;
+}
+
 static const struct pwm_ops vt8500_pwm_ops = {
-	.enable = vt8500_pwm_enable,
-	.disable = vt8500_pwm_disable,
-	.config = vt8500_pwm_config,
-	.set_polarity = vt8500_pwm_set_polarity,
+	.apply = vt8500_pwm_apply,
 	.owner = THIS_MODULE,
 };