Input: ads7846 - introduce platform specific way to synchronize sampling

Noises can be introduced when LCD signals are being driven, some platforms
provide a signal to assist the synchronization of this sampling procedure.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

2 files changed, 11 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 7c27c8b9b6d0..cf7e69766b2b 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -127,6 +127,8 @@ struct ads7846 {
         void                    (*filter_cleanup)(void *data);
         int                     (*get_pendown_state)(void);
         int                     gpio_pendown;
+
+        void                    (*wait_for_sync)(void);
 };
 
 /* leave chip selected when we're done, for quicker re-select? */
@@ -511,6 +513,10 @@ static int get_pendown_state(struct ads7846 *ts)
         return !gpio_get_value(ts->gpio_pendown);
 }
 
+static void null_wait_for_sync(void)
+{
+}
+
 /*
  * PENIRQ only kicks the timer.  The timer only reissues the SPI transfer,
  * to retrieve touchscreen status.
@@ -686,6 +692,7 @@ static void ads7846_rx_val(void *ads)
         default:
                 BUG();
         }
+        ts->wait_for_sync();
         status = spi_async(ts->spi, m);
         if (status)
                 dev_err(&ts->spi->dev, "spi_async --> %d\n",
@@ -723,6 +730,7 @@ static enum hrtimer_restart ads7846_timer(struct hrtimer *handle)
         } else {
                 /* pen is still down, continue with the measurement */
                 ts->msg_idx = 0;
+                ts->wait_for_sync();
                 status = spi_async(ts->spi, &ts->msg[0]);
                 if (status)
                         dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
@@ -947,6 +955,8 @@ static int __devinit ads7846_probe(struct spi_device *spi)
                 ts->penirq_recheck_delay_usecs =
                                 pdata->penirq_recheck_delay_usecs;
 
+        ts->wait_for_sync = pdata->wait_for_sync ? : null_wait_for_sync;
+
         snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&spi->dev));
 
         input_dev->name = "ADS784x Touchscreen";
diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
index 05eab2f11e63..2ea20320c093 100644
--- a/include/linux/spi/ads7846.h
+++ b/include/linux/spi/ads7846.h
@@ -51,5 +51,6 @@ struct ads7846_platform_data {
                                  void **filter_data);
         int     (*filter)       (void *filter_data, int data_idx, int *val);
         void    (*filter_cleanup)(void *filter_data);
+        void    (*wait_for_sync)(void);
 };