Input: ads7846 - add possibility to use external vref on ads7846

Just set vref_mv in your platform config to use external vref. Otherwise
the internal one is used.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

2 files changed, 13 insertions, 9 deletions

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index c24946f51256..e4ee43e159d2 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -109,6 +109,7 @@ struct ads7846 {
         u16                     pressure_max;
 
         bool                    swap_xy;
+        bool                    use_internal;
 
         struct ads7846_packet   *packet;
 
@@ -300,7 +301,6 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
         struct ads7846 *ts = dev_get_drvdata(dev);
         struct ser_req *req;
         int status;
-        int use_internal;
 
         req = kzalloc(sizeof *req, GFP_KERNEL);
         if (!req)
@@ -308,11 +308,8 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
 
         spi_message_init(&req->msg);
 
-        /* FIXME boards with ads7846 might use external vref instead ... */
-        use_internal = (ts->model == 7846);
-
         /* maybe turn on internal vREF, and let it settle */
-        if (use_internal) {
+        if (ts->use_internal) {
                 req->ref_on = REF_ON;
                 req->xfer[0].tx_buf = &req->ref_on;
                 req->xfer[0].len = 1;
@@ -324,8 +321,14 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
                 /* for 1uF, settle for 800 usec; no cap, 100 usec.  */
                 req->xfer[1].delay_usecs = ts->vref_delay_usecs;
                 spi_message_add_tail(&req->xfer[1], &req->msg);
+
+                /* Enable reference voltage */
+                command |= ADS_PD10_REF_ON;
         }
 
+        /* Enable ADC in every case */
+        command |= ADS_PD10_ADC_ON;
+
         /* take sample */
         req->command = (u8) command;
         req->xfer[2].tx_buf = &req->command;
@@ -409,7 +412,7 @@ name ## _show(struct device *dev, struct device_attribute *attr, char *buf) \
 { \
         struct ads7846 *ts = dev_get_drvdata(dev); \
         ssize_t v = ads7846_read12_ser(dev, \
-                        READ_12BIT_SER(var) | ADS_PD10_ALL_ON); \
+                        READ_12BIT_SER(var)); \
         if (v < 0) \
                 return v; \
         return sprintf(buf, "%u\n", adjust(ts, v)); \
@@ -502,6 +505,7 @@ static int ads784x_hwmon_register(struct spi_device *spi, struct ads7846 *ts)
                 if (!ts->vref_mv) {
                         dev_dbg(&spi->dev, "assuming 2.5V internal vREF\n");
                         ts->vref_mv = 2500;
+                        ts->use_internal = true;
                 }
                 break;
         case 7845:
@@ -1333,8 +1337,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
         if (ts->model == 7845)
                 ads7845_read12_ser(&spi->dev, PWRDOWN);
         else
-                (void) ads7846_read12_ser(&spi->dev,
-                                READ_12BIT_SER(vaux) | ADS_PD10_ALL_ON);
+                (void) ads7846_read12_ser(&spi->dev, READ_12BIT_SER(vaux));
 
         err = sysfs_create_group(&spi->dev.kobj, &ads784x_attr_group);
         if (err)
diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
index 92bd0839d5b4..c64de9dd7631 100644
--- a/include/linux/spi/ads7846.h
+++ b/include/linux/spi/ads7846.h
@@ -14,7 +14,8 @@ enum ads7846_filter {
 struct ads7846_platform_data {
         u16     model;                  /* 7843, 7845, 7846, 7873. */
         u16     vref_delay_usecs;       /* 0 for external vref; etc */
-        u16     vref_mv;                /* external vref value, milliVolts */
+        u16     vref_mv;                /* external vref value, milliVolts
+                                         * ads7846: if 0, use internal vref */
         bool    keep_vref_on;           /* set to keep vref on for differential
                                          * measurements as well */
         bool    swap_xy;                /* swap x and y axes */