Input: ads7846 - add support for AD7843 parts

The AD7873 is almost identical to the ADS7846; the only difference is
related to the Power Management bits PD0 and PD1.  This results in a
slightly different PENIRQ enable behavior.  For the AD7873, VREF should
be turned off during differential measurements.

So, add the AD7873/43 to the list of driver supported devices, and prevent
VREF usage during differential/ratiometric conversion modes.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

2 files changed, 15 insertions, 4 deletions

diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
index 7208654a94ae..8a8fa4d2d6a8 100644
--- a/drivers/input/touchscreen/Kconfig
+++ b/drivers/input/touchscreen/Kconfig
@@ -24,17 +24,18 @@ config TOUCHSCREEN_88PM860X
           module will be called 88pm860x-ts.
 
 config TOUCHSCREEN_ADS7846
-        tristate "ADS7846/TSC2046 and ADS7843 based touchscreens"
+        tristate "ADS7846/TSC2046/AD7873 and AD(S)7843 based touchscreens"
         depends on SPI_MASTER
         depends on HWMON = n || HWMON
         help
           Say Y here if you have a touchscreen interface using the
-          ADS7846/TSC2046 or ADS7843 controller, and your board-specific
-          setup code includes that in its table of SPI devices.
+          ADS7846/TSC2046/AD7873 or ADS7843/AD7843 controller,
+          and your board-specific setup code includes that in its
+          table of SPI devices.
 
           If HWMON is selected, and the driver is told the reference voltage
           on your board, you will also get hwmon interfaces for the voltage
-          (and on ads7846/tsc2046, temperature) sensors of this chip.
+          (and on ads7846/tsc2046/ad7873, temperature) sensors of this chip.
 
           If unsure, say N (but it's safe to say "Y").
 
diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 8b05d8e97543..d187be05955f 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -36,6 +36,7 @@
  * TSC2046 is just newer ads7846 silicon.
  * Support for ads7843 tested on Atmel at91sam926x-EK.
  * Support for ads7845 has only been stubbed in.
+ * Support for Analog Devices AD7873 and AD7843 tested.
  *
  * IRQ handling needs a workaround because of a shortcoming in handling
  * edge triggered IRQs on some platforms like the OMAP1/2. These
@@ -984,6 +985,15 @@ static int __devinit ads7846_probe(struct spi_device *spi)
 
         vref = pdata->keep_vref_on;
 
+        if (ts->model == 7873) {
+                /* The AD7873 is almost identical to the ADS7846
+                 * keep VREF off during differential/ratiometric
+                 * conversion modes
+                 */
+                ts->model = 7846;
+                vref = 0;
+        }
+
         /* set up the transfers to read touchscreen state; this assumes we
          * use formula #2 for pressure, not #3.
          */