ARM: pxa: magician: Add support for ADS7846 touchscreen

This patch adds a support for ADS7846 touchscreen driver.

The basic functionality was tested, x_plate_ohms and y_plate_ohms were physically measured. The value pressure_max was empirically set to match the measured range, which is affected by x_plate_ohms and ADS samples.

The value of keep_vref_on should be set. A tested model (T-Mobile MDA Compact PM10A) doesn't seem to use Vref pin as the input from an external source. On this model the unset keep_vref_on cause high jitter of measured values.

SPI framing pin (gpio_cs) must be used in GPIO mode due to an incompatible autoframing of PXA27x controller and ADS7846 device.

---
 arch/arm/mach-pxa/include/mach/magician.h |  1 +
 arch/arm/mach-pxa/magician.c              | 84 ++++++++++++++++++++++++++++++-
 2 files changed, 84 insertions(+), 1 deletion(-)

index 5f6b850ebe33..c48b54d0f331 100644
@@ -24,6 +24,7 @@
 #define GPIO10_MAGICIAN_GSM_IRQ			10
 #define GPIO11_MAGICIAN_GSM_OUT1		11
 #define GPIO13_MAGICIAN_CPLD_IRQ		13
+#define GPIO14_MAGICIAN_TSC2046_CS		14
 #define GPIO18_MAGICIAN_UNKNOWN			18
 #define GPIO22_MAGICIAN_VIBRA_EN		22
 #define GPIO26_MAGICIAN_GSM_POWER		26

2.11.0

Applied to pxa/for-next, unless Philipp objects in the next couple of days, thanks.

Cheers.

--
Robert