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Subject[PATCH v2 3/3] pwm: stm32: add power management support
Date
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>
---
Changes in v2:
Follow Uwe suggestions/remarks:
- Add a precursor patch to ease reviewing
- Use registers read instead of pwm_get_state
- Add a comment to mention registers content may be lost in low power mode
---
drivers/pwm/pwm-stm32.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)

diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
index cf8658c..546b661 100644
--- 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>

@@ -655,6 +656,42 @@ 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 ch;
+ u32 ccer, mask;
+
+ /* Look for active channels */
+ ccer = active_channels(priv);
+
+ for (ch = 0; ch < priv->chip.npwm; ch++) {
+ mask = TIM_CCER_CC1E << (ch * 4);
+ if (ccer & mask) {
+ dev_err(dev, "The consumer didn't stop us (%s)\n",
+ priv->chip.pwms[ch].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 */ },
@@ -667,6 +704,7 @@ 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);
--
2.7.4
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