[PATCH v3] ARM: pxa: magician: Add support for ADS7846 touchscreen

Petr Cvek [off-list ref] writes:

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.

Signed-off-by: Petr Cvek <redacted>

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

Cheers.

--
Robert