Input: ads7846 - power down ADC a bit later

Submit a seperate request for powering down the ADC in ads7846,
doing it after the last read request.  Otherwise some of the read
values are incorrect.

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

1 files changed, 18 insertions, 3 deletions

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 7f384a694d80..54d433477860 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -72,10 +72,11 @@ struct ads7846 {
         u16                     vref_delay_usecs;
         u16                     x_plate_ohms;
 
-        u8                      read_x, read_y, read_z1, read_z2;
+        u8                      read_x, read_y, read_z1, read_z2, pwrdown;
+        u16                     dummy;          /* for the pwrdown read */
         struct ts_event         tc;
 
-        struct spi_transfer     xfer[8];
+        struct spi_transfer     xfer[10];
         struct spi_message      msg;
 
         spinlock_t              lock;
@@ -125,7 +126,9 @@ struct ads7846 {
 #define READ_Y  (READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON)
 #define READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
 #define READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
-#define READ_X  (READ_12BIT_DFR(x)  | ADS_PD10_PDOWN)   /* LAST */
+
+#define READ_X  (READ_12BIT_DFR(x)  | ADS_PD10_ADC_ON)
+#define PWRDOWN (READ_12BIT_DFR(y)  | ADS_PD10_PDOWN)   /* LAST */
 
 /* single-ended samples need to first power up reference voltage;
  * we leave both ADC and VREF powered
@@ -541,6 +544,18 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         x++;
         x->rx_buf = &ts->tc.x;
         x->len = 2;
+        spi_message_add_tail(x, &ts->msg);
+
+        /* power down */
+        x++;
+        ts->pwrdown = PWRDOWN;
+        x->tx_buf = &ts->pwrdown;
+        x->len = 1;
+        spi_message_add_tail(x, &ts->msg);
+
+        x++;
+        x->rx_buf = &ts->dummy;
+        x->len = 2;
         CS_CHANGE(*x);
         spi_message_add_tail(x, &ts->msg);