MFD: ucb1x00-ts: fix resume failure

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>

1 files changed, 5 insertions, 27 deletions

diff --git a/drivers/mfd/ucb1x00-ts.c b/drivers/mfd/ucb1x00-ts.c
index 38ffbd50a0d2..63a3cbdfa3f3 100644
--- a/drivers/mfd/ucb1x00-ts.c
+++ b/drivers/mfd/ucb1x00-ts.c
@@ -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)