Input: ads7846: switch to 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>

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 94c36b1a7f2600221e888cd880150a6a11151a3b..008cf0a83a5408fb71411ad4cbe16036b0724a7d 100644 (file)
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -55,7 +55,8 @@
  * 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 */)
@@ -100,7 +101,7 @@ 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"
@@ -448,7 +449,8 @@ static void ads7846_rx(void *ads)
                pr_debug("%s: ignored %d pressure %d\n",
                        ts->spi->dev.bus_id, ts->tc.ignore, Rt);
 #endif
-               mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
+               hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD),
+                             HRTIMER_REL);
                return;
        }
 
@@ -468,7 +470,7 @@ static void ads7846_rx(void *ads)
        }
 
 
-       mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
+       hrtimer_start(&ts->timer, ktime_set(0, TS_POLL_PERIOD), HRTIMER_REL);
 }
 
 static void ads7846_debounce(void *ads)
@@ -523,9 +525,9 @@ static void ads7846_debounce(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);
@@ -553,6 +555,7 @@ static void ads7846_timer(unsigned long handle)
        }
 
        spin_unlock_irq(&ts->lock);
+       return HRTIMER_NORESTART;
 }
 
 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
@@ -572,7 +575,8 @@ static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
                        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);
@@ -709,8 +713,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        ts->input = input_dev;
        ts->hwmon = hwmon;
 
-       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);