pwm: stm32: Add power management support

Add suspend/resume PM sleep ops. When going to low power, enforce the PWM
channel isn't active. Let the PWM consumers disable it during their own
suspend sequence, see [1]. So, perform a check here, and handle the
pinctrl states. Also restore the break inputs upon resume, as registers
content may be lost when going to low power mode.

[1] https://lkml.org/lkml/2019/2/5/770

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
index dd0b277..9430b4c 100644 (file)
--- a/drivers/pwm/pwm-stm32.c
+++ b/drivers/pwm/pwm-stm32.c
@@ -12,6 +12,7 @@
 #include <linux/mfd/stm32-timers.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
 
@@ -659,6 +660,42 @@ static int stm32_pwm_remove(struct platform_device *pdev)
        return 0;
 }
 
+static int __maybe_unused stm32_pwm_suspend(struct device *dev)
+{
+       struct stm32_pwm *priv = dev_get_drvdata(dev);
+       unsigned int i;
+       u32 ccer, mask;
+
+       /* Look for active channels */
+       ccer = active_channels(priv);
+
+       for (i = 0; i < priv->chip.npwm; i++) {
+               mask = TIM_CCER_CC1E << (i * 4);
+               if (ccer & mask) {
+                       dev_err(dev, "PWM %u still in use by consumer %s\n",
+                               i, priv->chip.pwms[i].label);
+                       return -EBUSY;
+               }
+       }
+
+       return pinctrl_pm_select_sleep_state(dev);
+}
+
+static int __maybe_unused stm32_pwm_resume(struct device *dev)
+{
+       struct stm32_pwm *priv = dev_get_drvdata(dev);
+       int ret;
+
+       ret = pinctrl_pm_select_default_state(dev);
+       if (ret)
+               return ret;
+
+       /* restore breakinput registers that may have been lost in low power */
+       return stm32_pwm_apply_breakinputs(priv);
+}
+
+static SIMPLE_DEV_PM_OPS(stm32_pwm_pm_ops, stm32_pwm_suspend, stm32_pwm_resume);
+
 static const struct of_device_id stm32_pwm_of_match[] = {
        { .compatible = "st,stm32-pwm", },
        { /* end node */ },
@@ -671,6 +708,7 @@ static struct platform_driver stm32_pwm_driver = {
        .driver = {
                .name = "stm32-pwm",
                .of_match_table = stm32_pwm_of_match,
+               .pm = &stm32_pwm_pm_ops,
        },
 };
 module_platform_driver(stm32_pwm_driver);