This allows maximum flexibility for configuring the direct GPIO based
interrupts.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

If the WM831x pen down and data IRQs run in parallel it is possible for the
data and pen down IRQs to deadlock themselves as one is part way through
disabling its operation while the other is part way through enabling. Fix
this by always disabling the pen down interrupt while data is active and
vice versa.  When a changeover is required we disable the IRQ that is to
be stopped then schedule work that will enable the new IRQ.

We need to handle the data flow in the data IRQ as the readback from the
device needs to be ordered correctly with the IRQ for robust operation.

This also fixes an issue when using the built in IRQs due to enable_irq()
not being valid from interrupt context on an interrupt controller with bus
operations like the built in IRQ controller - this issue may also have
affected other interrupt controllers.  We can't rely on having the data
and pen down IRQs available via GPIOs on the CPU on every system.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

Explicitly set all the enable bits when opening the device just in case
something left the device in an unexpected state.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

tslib expects pressure measurements so enable them by default for better
compatibility.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

While being applied the driver was modified to add use of the ternary
operator. Write the conditionals out longhand as I find it terribly
unhelpful for legibility.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

Some of the WM831x series of PMICs from Wolfson Microelectronics include
a resistive touchscreen controller. Implement support for these controllers
within the input API.

Platform data is supported to allow configuration of system parameters such
as selection between four and five wire touchscreens and for specification
of optional direct to CPU IRQs for sample availability and for pen down.
Use of this feature for at least the data IRQ is strongly recommended.

Thanks to Julien Boibessot for extensive testing and detailed feedback.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Tested-by: NJulien Boibessot <julien.boibessot@armadeus.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>