[PATCH v2] pwm: renesas-tpu: Add suspend/resume function

[Cao Van Dong <cv-dong@jinso.co.jp>]

This patch adds suspend/resume function support for Renesas the 16-Bit Timer
Pulse Unit (TPU) driver. This has been tested on the Salvator-XS board 
with R-Car M3-N and H3 at renesas-drivers-2019-05-21-v5.2-rc1 tag.
I expect this to work on other SoCs.

Test procedure:
  - Enable TPU and pin control in DTS.
  - Make sure switches { SW29-[1-2] are switched off or 
    SW31-[1-4] are switched off(only for Salvator-xs) }.
  - Exercise userspace PWM control for pwm[2,3] 
    of /sys/class/pwm/pwmchip1/ .
  - Inspect PWM signals on the input side of { CN29-[58,60] 
    or SW31-[1,2] (only for Salvator-xs) }
    before and after suspend/resume using an oscilloscope. 

Signed-off-by: Cao Van Dong <cv-dong@jinso.co.jp>
Tested-by: Cao Van Dong <cv-dong@jinso.co.jp>
---
Changes v1 -> v2:
  - Repair the handling code to cover case of using multiple timers.
---
 drivers/pwm/pwm-renesas-tpu.c | 55 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/pwm/pwm-renesas-tpu.c b/drivers/pwm/pwm-renesas-tpu.c
index 4a855a2..a6660cc 100644
--- a/drivers/pwm/pwm-renesas-tpu.c
+++ b/drivers/pwm/pwm-renesas-tpu.c
@@ -366,6 +366,60 @@ static void tpu_pwm_disable(struct pwm_chip *chip, struct pwm_device *_pwm)
 	tpu_pwm_timer_stop(pwm);
 }
 
+#ifdef CONFIG_PM_SLEEP
+static int tpu_pwm_restart_timer(struct pwm_device *pwm)
+{
+	if (!test_bit(PWMF_REQUESTED, &pwm->flags))
+		return 0;
+
+	/* Restart timer */
+	tpu_pwm_disable(pwm->chip,pwm);
+	tpu_pwm_enable(pwm->chip,pwm);
+
+	return 0;
+}
+
+static int tpu_pwm_suspend(struct device *dev)
+{
+	struct tpu_device *tpu = dev_get_drvdata(dev);
+	struct pwm_chip *chip = &tpu->chip;
+	struct pwm_device *pwm;
+	int i;
+
+	for (i = 0; i <= 3; i++) {
+		if ((pwm_get_chip_data(&chip->pwms[i])) != NULL) {
+			pwm = &chip->pwms[i];
+			if (!test_bit(PWMF_REQUESTED, &pwm->flags))
+				return 0;
+		}
+	}
+
+	pm_runtime_put(dev);
+
+	return 0;
+}
+
+static int tpu_pwm_resume(struct device *dev)
+{
+	struct tpu_device *tpu = dev_get_drvdata(dev);
+	struct pwm_chip *chip = &tpu->chip;
+	struct pwm_device *pwm;
+	int i;
+
+	pm_runtime_get_sync(dev);
+
+	for (i = 0; i <= 3; i++) {
+		if ((pwm_get_chip_data(&chip->pwms[i])) != NULL) {
+			pwm = &chip->pwms[i];
+			tpu_pwm_restart_timer(pwm);
+		}
+	}
+
+	return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+static SIMPLE_DEV_PM_OPS(tpu_pwm_pm_ops, tpu_pwm_suspend, tpu_pwm_resume);
+
 static const struct pwm_ops tpu_pwm_ops = {
 	.request = tpu_pwm_request,
 	.free = tpu_pwm_free,
@@ -459,6 +513,7 @@ static struct platform_driver tpu_driver = {
 	.remove		= tpu_remove,
 	.driver		= {
 		.name	= "renesas-tpu-pwm",
+		.pm	= &tpu_pwm_pm_ops,
 		.of_match_table = of_match_ptr(tpu_of_table),
 	}
 };
-- 
2.7.4