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-rw-r--r--drivers/input/touchscreen/ads7846.c65
-rw-r--r--include/linux/spi/ads7846.h8
2 files changed, 72 insertions, 1 deletions
diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 1c9069cd3bae..103ee6ad299e 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -95,7 +95,7 @@ struct ads7846 {
u16 dummy; /* for the pwrdown read */
struct ts_event tc;
- struct spi_transfer xfer[10];
+ struct spi_transfer xfer[18];
struct spi_message msg[5];
struct spi_message *last_msg;
int msg_idx;
@@ -936,6 +936,24 @@ static int __devinit ads7846_probe(struct spi_device *spi)
x->len = 2;
spi_message_add_tail(x, m);
+ /* the first sample after switching drivers can be low quality;
+ * optionally discard it, using a second one after the signals
+ * have had enough time to stabilize.
+ */
+ if (pdata->settle_delay_usecs) {
+ x->delay_usecs = pdata->settle_delay_usecs;
+
+ x++;
+ x->tx_buf = &ts->read_y;
+ x->len = 1;
+ spi_message_add_tail(x, m);
+
+ x++;
+ x->rx_buf = &ts->tc.y;
+ x->len = 2;
+ spi_message_add_tail(x, m);
+ }
+
m->complete = ads7846_rx_val;
m->context = ts;
@@ -954,6 +972,21 @@ static int __devinit ads7846_probe(struct spi_device *spi)
x->len = 2;
spi_message_add_tail(x, m);
+ /* ... maybe discard first sample ... */
+ if (pdata->settle_delay_usecs) {
+ x->delay_usecs = pdata->settle_delay_usecs;
+
+ x++;
+ x->tx_buf = &ts->read_x;
+ x->len = 1;
+ spi_message_add_tail(x, m);
+
+ x++;
+ x->rx_buf = &ts->tc.x;
+ x->len = 2;
+ spi_message_add_tail(x, m);
+ }
+
m->complete = ads7846_rx_val;
m->context = ts;
@@ -973,6 +1006,21 @@ static int __devinit ads7846_probe(struct spi_device *spi)
x->len = 2;
spi_message_add_tail(x, m);
+ /* ... maybe discard first sample ... */
+ if (pdata->settle_delay_usecs) {
+ x->delay_usecs = pdata->settle_delay_usecs;
+
+ x++;
+ x->tx_buf = &ts->read_z1;
+ x->len = 1;
+ spi_message_add_tail(x, m);
+
+ x++;
+ x->rx_buf = &ts->tc.z1;
+ x->len = 2;
+ spi_message_add_tail(x, m);
+ }
+
m->complete = ads7846_rx_val;
m->context = ts;
@@ -990,6 +1038,21 @@ static int __devinit ads7846_probe(struct spi_device *spi)
x->len = 2;
spi_message_add_tail(x, m);
+ /* ... maybe discard first sample ... */
+ if (pdata->settle_delay_usecs) {
+ x->delay_usecs = pdata->settle_delay_usecs;
+
+ x++;
+ x->tx_buf = &ts->read_z2;
+ x->len = 1;
+ spi_message_add_tail(x, m);
+
+ x++;
+ x->rx_buf = &ts->tc.z2;
+ x->len = 2;
+ spi_message_add_tail(x, m);
+ }
+
m->complete = ads7846_rx_val;
m->context = ts;
}
diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
index 3387e44dfd13..a44fa7a02bd9 100644
--- a/include/linux/spi/ads7846.h
+++ b/include/linux/spi/ads7846.h
@@ -16,6 +16,14 @@ struct ads7846_platform_data {
u16 vref_delay_usecs; /* 0 for external vref; etc */
int keep_vref_on:1; /* set to keep vref on for differential
* measurements as well */
+
+ /* Settling time of the analog signals; a function of Vcc and the
+ * capacitance on the X/Y drivers. If set to non-zero, two samples
+ * are taken with settle_delay us apart, and the second one is used.
+ * ~150 uSec with 0.01uF caps.
+ */
+ u16 settle_delay_usecs;
+
u16 x_plate_ohms;
u16 y_plate_ohms;