[PATCH] Input: pwm-beeper - defer pwm config if pwm can sleep

From: Manfred Schlaegl
Date: Wed Feb 17 2016 - 08:19:42 EST


If the pwm can sleep defer actions to it using a worker.
A similar approach was used in leds-pwm (c971ff185)

Trigger:
On a Freescale i.MX53 based board we ran into "BUG: scheduling while
atomic" because input_inject_event locks interrupts, but
imx_pwm_config_v2 sleeps.

Tested on Freescale i.MX53 SoC with 4.5-rc1 and 4.1.

Unmodified applicable to
* 4.5-rc4
* 4.4.1 (stable)
* 4.3.5 (stable)
* 4.1.18 (longterm)

Modified applicable to
* 3.18.27 (longterm)

Signed-off-by: Manfred Schlaegl <manfred.schlaegl@xxxxxx>
---
drivers/input/misc/pwm-beeper.c | 62 +++++++++++++++++++++++++++++------------
1 file changed, 44 insertions(+), 18 deletions(-)

diff --git a/drivers/input/misc/pwm-beeper.c b/drivers/input/misc/pwm-beeper.c
index f2261ab..c160b5e 100644
--- a/drivers/input/misc/pwm-beeper.c
+++ b/drivers/input/misc/pwm-beeper.c
@@ -20,21 +20,42 @@
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
+#include <linux/workqueue.h>

struct pwm_beeper {
struct input_dev *input;
struct pwm_device *pwm;
+ struct work_struct work;
unsigned long period;
+ bool can_sleep;
};

#define HZ_TO_NANOSECONDS(x) (1000000000UL/(x))

+static void __pwm_beeper_set(struct pwm_beeper *beeper)
+{
+ unsigned long period = beeper->period;
+
+ pwm_config(beeper->pwm, period / 2, period);
+
+ if (period == 0)
+ pwm_disable(beeper->pwm);
+ else
+ pwm_enable(beeper->pwm);
+}
+
+static void pwm_beeper_work(struct work_struct *work)
+{
+ struct pwm_beeper *beeper =
+ container_of(work, struct pwm_beeper, work);
+
+ __pwm_beeper_set(beeper);
+}
+
static int pwm_beeper_event(struct input_dev *input,
unsigned int type, unsigned int code, int value)
{
- int ret = 0;
struct pwm_beeper *beeper = input_get_drvdata(input);
- unsigned long period;

if (type != EV_SND || value < 0)
return -EINVAL;
@@ -49,18 +70,15 @@ static int pwm_beeper_event(struct input_dev *input,
return -EINVAL;
}

- if (value == 0) {
- pwm_disable(beeper->pwm);
- } else {
- period = HZ_TO_NANOSECONDS(value);
- ret = pwm_config(beeper->pwm, period / 2, period);
- if (ret)
- return ret;
- ret = pwm_enable(beeper->pwm);
- if (ret)
- return ret;
- beeper->period = period;
- }
+ if (value == 0)
+ beeper->period = 0;
+ else
+ beeper->period = HZ_TO_NANOSECONDS(value);
+
+ if (beeper->can_sleep)
+ schedule_work(&beeper->work);
+ else
+ __pwm_beeper_set(beeper);

return 0;
}
@@ -87,6 +105,10 @@ static int pwm_beeper_probe(struct platform_device *pdev)
goto err_free;
}

+ beeper->can_sleep = pwm_can_sleep(beeper->pwm);
+ if (beeper->can_sleep)
+ INIT_WORK(&beeper->work, pwm_beeper_work);
+
beeper->input = input_allocate_device();
if (!beeper->input) {
dev_err(&pdev->dev, "Failed to allocate input device\n");
@@ -133,6 +155,9 @@ static int pwm_beeper_remove(struct platform_device *pdev)
{
struct pwm_beeper *beeper = platform_get_drvdata(pdev);

+ if (beeper->can_sleep)
+ cancel_work_sync(&beeper->work);
+
input_unregister_device(beeper->input);

pwm_disable(beeper->pwm);
@@ -147,6 +172,9 @@ static int __maybe_unused pwm_beeper_suspend(struct device *dev)
{
struct pwm_beeper *beeper = dev_get_drvdata(dev);

+ if (beeper->can_sleep)
+ cancel_work_sync(&beeper->work);
+
if (beeper->period)
pwm_disable(beeper->pwm);

@@ -157,10 +185,8 @@ static int __maybe_unused pwm_beeper_resume(struct device *dev)
{
struct pwm_beeper *beeper = dev_get_drvdata(dev);

- if (beeper->period) {
- pwm_config(beeper->pwm, beeper->period / 2, beeper->period);
- pwm_enable(beeper->pwm);
- }
+ if (beeper->period)
+ __pwm_beeper_set(beeper);

return 0;
}
--
2.1.4