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MFD: ucb1x00-ts: fix resume failure

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If the ucb1x00 touchscreen is resumed while the touchscreen is being
touched, the main thread stops responding.  This occurs because two
things happen:

1. When we suspended, we were woken up, and executed the loop.
   Finding that the touchscreen was not pressed, we prepare to
   schedule for a maximum timeout, before being stopped in
   try_to_freeze().

2. an irq occurs, we disable the irq, and mark it as disabled,
   and wake the thread.  This wake occurs while the thread is
   still within __refrigerator()

3. The thread is unfrozen, and __refrigerator() sets the threads
   state back to INTERRUPTIBLE.

We then drop into schedule_timeout() with an infinite timeout and the
IRQ disabled.  This prevents any further screen touches activating
the thread.

Fix this by using kthread_freezable_should_stop() which handles the
freezing issues for us outside of the hotspot where the task state
matters.  Include a flag to ignore the touchscreen until it is
released to avoid sending unintended data to the application.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2012-01-22 20:58:55 +00:00
parent c23bb602af
commit 0af5e4c36e
1 changed files with 5 additions and 27 deletions
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32
drivers/mfd/ucb1x00-ts.c
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@ -47,7 +47,6 @@ struct ucb1x00_ts {
u16 x_res;
u16 y_res;
unsigned int restart:1;
unsigned int adcsync:1;
};
@ -207,15 +206,17 @@ static int ucb1x00_thread(void *_ts)
{
struct ucb1x00_ts *ts = _ts;
DECLARE_WAITQUEUE(wait, current);
bool frozen, ignore = false;
int valid = 0;
set_freezable();
add_wait_queue(&ts->irq_wait, &wait);
while (!kthread_should_stop()) {
while (!kthread_freezable_should_stop(&frozen)) {
unsigned int x, y, p;
signed long timeout;
ts->restart = 0;
if (frozen)
ignore = true;
ucb1x00_adc_enable(ts->ucb);
@ -258,7 +259,7 @@ static int ucb1x00_thread(void *_ts)
* space. We therefore leave it to user space
* to do any filtering they please.
*/
if (!ts->restart) {
if (!ignore) {
ucb1x00_ts_evt_add(ts, p, x, y);
valid = 1;
}
@ -267,8 +268,6 @@ static int ucb1x00_thread(void *_ts)
timeout = HZ / 100;
}
try_to_freeze();
schedule_timeout(timeout);
}
@ -340,26 +339,6 @@ static void ucb1x00_ts_close(struct input_dev *idev)
ucb1x00_disable(ts->ucb);
}
#ifdef CONFIG_PM
static int ucb1x00_ts_resume(struct ucb1x00_dev *dev)
{
struct ucb1x00_ts *ts = dev->priv;
if (ts->rtask != NULL) {
/*
* Restart the TS thread to ensure the
* TS interrupt mode is set up again
* after sleep.
*/
ts->restart = 1;
wake_up(&ts->irq_wait);
}
return 0;
}
#else
#define ucb1x00_ts_resume NULL
#endif
/*
* Initialisation.
@ -425,7 +404,6 @@ static void ucb1x00_ts_remove(struct ucb1x00_dev *dev)
static struct ucb1x00_driver ucb1x00_ts_driver = {
.add = ucb1x00_ts_add,
.remove = ucb1x00_ts_remove,
.resume = ucb1x00_ts_resume,
};
static int __init ucb1x00_ts_init(void)