pwm: atmel: Make use of devm_pwmchip_alloc() function

This prepares the pwm-atmel driver to further changes of the pwm core
outlined in the commit introducing devm_pwmchip_alloc(). There is no
intended semantical change and the driver should behave as before.

Link: https://lore.kernel.org/r/f2a83af5660de461b4dcaf76929e9813bddfeff1.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-atmel.c

@@ -77,7 +77,6 @@ struct atmel_pwm_data {
 };
 
 struct atmel_pwm_chip {
-	struct pwm_chip chip;
 	struct clk *clk;
 	void __iomem *base;
 	const struct atmel_pwm_data *data;
@@ -99,7 +98,7 @@ struct atmel_pwm_chip {
 
 static inline struct atmel_pwm_chip *to_atmel_pwm_chip(struct pwm_chip *chip)
 {
-	return container_of(chip, struct atmel_pwm_chip, chip);
+	return pwmchip_get_drvdata(chip);
 }
 
 static inline u32 atmel_pwm_readl(struct atmel_pwm_chip *chip,
@@ -502,10 +501,11 @@ static int atmel_pwm_probe(struct platform_device *pdev)
 	struct pwm_chip *chip;
 	int ret;
 
-	atmel_pwm = devm_kzalloc(&pdev->dev, sizeof(*atmel_pwm), GFP_KERNEL);
-	if (!atmel_pwm)
-		return -ENOMEM;
+	chip = devm_pwmchip_alloc(&pdev->dev, 4, sizeof(*atmel_pwm));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
 
+	atmel_pwm = to_atmel_pwm_chip(chip);
 	atmel_pwm->data = of_device_get_match_data(&pdev->dev);
 
 	atmel_pwm->update_pending = 0;
@@ -520,10 +520,7 @@ static int atmel_pwm_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, PTR_ERR(atmel_pwm->clk),
 				     "failed to get prepared PWM clock\n");
 
-	chip = &atmel_pwm->chip;
-	chip->dev = &pdev->dev;
 	chip->ops = &atmel_pwm_ops;
-	chip->npwm = 4;
 
 	ret = atmel_pwm_enable_clk_if_on(chip, true);
 	if (ret < 0)