Input: ads7846 - introduce sample settling delay

[linux-2.6-omap-h63xx.git] / drivers / input / touchscreen / ads7846.c

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 1c9069cd3bae4228fe1ed142c8c6543b4467ad11..103ee6ad299e0ea4d2bd2941918343aa5b7442bf 100644 (file)
--- 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;
        }