[PATCHv5] staging/iio/adc: change the MXS touchscreen driver implementation

[marex@denx.de (Marek Vasut)]

Dear Juergen Beisert,

> The following series replaces the current busy loop touchscreen
> implementation for i.MX28/i.MX23 SoCs by a fully interrupt driven
> implementation.
> 
> Since i.MX23 and i.MX28 silicon differs, the existing implementation can
> be used for the i.MX28 SoC only.
> 
> So, the first two patches of this series move the i.MX28 specific
> definitions out of the way. The third patch simplifies the register access
> to make it easier to add the i.MX23 support. Then the i.MX23 specific
> definitions are added, also the code to distinguish both SoCs at run-time.
> Up to here the existing touchscreen driver will now run on an i.MX23 Soc as
> well.
> 
> When the i.MX23 SoC is running from battery it seems not to be a good idea
> to run a busy loop to detect touches and their location. The fourth patch
> adds a fully interrupt driven implementation which makes use of the
> built-in delay and multiple sample features of the touchscreen controller.
> This will reduce the interrupt load to a minimum.
> 
> The next to last patch in this series just removes the existing busy loop
> implementation.
> 
> The last patch adds a devicetree bindings proposal (to be discussed).
> 
> Some restrictions/questions:
> 
> - the touchscreen part is yet tested on i.MX23 SoC only
> - has someone a good idea how to implement a reliable pressure measurement
> if the resistances of the touchscreen's plates are unknown?
> 
> Changes since v4:
> 
> - honor Jonathan's comments about function names
> - honor Dmitry's comments about workqueue canceling and interrupts
> - adding devicetree bindings proposal
> 
> Changes since v3:
> 
> - split adding register access functions and i.MX23 support into two
> patches
> 
> Changes since v2:
> 
> - useless debug output removed
> 
> Changes since v1:
> 
> - adding register access functions to make the existing code more readable
> - adding some functions to distinguish the SoCs at run-time to avoid
> if-else contructs whenever differences in the register layout between
> i.MX23 and i.MX28 must be handled

Just tested this on M28EVK, the touchscreen is dead. I do not get any touch 
events when I use ts_calibrate and when I hd /dev/input/eventX , I get nothing 
either.

Right now, I'm somehow on a tight schedule, but I'd like to see this resolved 
ASAP. Do you have any hint for me ?

btw. the touchscreen connection on M28EVK is pretty much the same as on MX28EVK.

Best regards,
Marek Vasut