Input: ads7846 - switch to using hrtimer

Use hrtimer instead of the normal timer, since it provides better
sampling resolution. This will:

 - avoid a problem where we have a 1 jiffy poll period and
   dynamic tick on
 - utilize high resolution HW clocks when they are added to
   the hrtimer framework

Signed-off-by: Imre Deak <imre.deak@solidboot.com>
Signed-off-by: Juha Yrjola <juha.yrjola@solidboot.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 15 insertions, 11 deletions

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index c34e59b720a6..d983cc51ad32 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -54,7 +54,8 @@
  * files.
  */
 
-#define TS_POLL_PERIOD  msecs_to_jiffies(10)
+#define TS_POLL_DELAY   (1 * 1000000)   /* ns delay before the first sample */
+#define TS_POLL_PERIOD  (5 * 1000000)   /* ns delay between samples */
 
 /* this driver doesn't aim at the peak continuous sample rate */
 #define SAMPLE_BITS     (8 /*cmd*/ + 16 /*sample*/ + 2 /* before, after */)
@@ -99,7 +100,7 @@ struct ads7846 {
         u16                     debounce_rep;
 
         spinlock_t              lock;
-        struct timer_list       timer;          /* P: lock */
+        struct hrtimer          timer;
         unsigned                pendown:1;      /* P: lock */
         unsigned                pending:1;      /* P: lock */
 // FIXME remove "irq_disabled"
@@ -407,10 +408,12 @@ static void ads7846_rx(void *ads)
                 Rt = 0;
 
         /* Sample found inconsistent by debouncing or pressure is beyond
-        * the maximum. Don't report it to user space, repeat at least
-        * once more the measurement */
+         * the maximum. Don't report it to user space, repeat at least
+         * once more the measurement
+         */
         if (ts->tc.ignore || Rt > ts->pressure_max) {
-                mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
+                hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),
+                              HRTIMER_REL);
                 return;
         }
 
@@ -452,7 +455,7 @@ static void ads7846_rx(void *ads)
         spin_lock_irqsave(&ts->lock, flags);
 
         ts->pendown = (Rt != 0);
-        mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
+        hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD), HRTIMER_REL);
 
         spin_unlock_irqrestore(&ts->lock, flags);
 }
@@ -543,9 +546,9 @@ static void ads7846_rx_val(void *ads)
                                 status);
 }
 
-static void ads7846_timer(unsigned long handle)
+static int ads7846_timer(struct hrtimer *handle)
 {
-        struct ads7846  *ts = (void *)handle;
+        struct ads7846  *ts = container_of(handle, struct ads7846, timer);
         int             status = 0;
 
         spin_lock_irq(&ts->lock);
@@ -567,6 +570,7 @@ static void ads7846_timer(unsigned long handle)
         }
 
         spin_unlock_irq(&ts->lock);
+        return HRTIMER_NORESTART;
 }
 
 static irqreturn_t ads7846_irq(int irq, void *handle)
@@ -585,7 +589,8 @@ static irqreturn_t ads7846_irq(int irq, void *handle)
                         ts->irq_disabled = 1;
                         disable_irq(ts->spi->irq);
                         ts->pending = 1;
-                        mod_timer(&ts->timer, jiffies);
+                        hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_DELAY),
+                                        HRTIMER_REL);
                 }
         }
         spin_unlock_irqrestore(&ts->lock, flags);
@@ -719,8 +724,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         ts->spi = spi;
         ts->input = input_dev;
 
-        init_timer(&ts->timer);
-        ts->timer.data = (unsigned long) ts;
+        hrtimer_init(&ts->timer, CLOCK_MONOTONIC, HRTIMER_REL);
         ts->timer.function = ads7846_timer;
 
         spin_lock_init(&ts->lock);