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The SADC component in JZ47xx SoCs provides support for touchscreen operations (pen position and pen down pressure) in single-ended and differential modes. The touchscreen component of SADC takes a significant time to stabilize after first receiving the clock and a delay of 50ms has been empirically proven to be a safe value before data sampling can begin. Of the known hardware to use this controller, GCW Zero and Anbernic RG-350 utilize the touchscreen mode by having their joystick(s) attached to the X/Y positive/negative input pins. JZ4770 and later SoCs introduce a low-level command feature. With it, up to 32 commands can be programmed, each one corresponding to a sampling job. It allows to change the low-voltage reference, the high-voltage reference, have them connected to VCC, GND, or one of the X-/X+ or Y-/Y+ pins. This patch introduces support for 6 stream-capable channels: - channel #0 samples X+/GND - channel #1 samples Y+/GND - channel #2 samples X-/GND - channel #3 samples Y-/GND - channel #4 samples X+/X- - channel #5 samples Y+/Y- Being able to sample X-/GND and Y-/GND is useful on some devices, where one joystick is connected to the X+/Y+ pins, and a second joystick is connected to the X-/Y- pins. All the boards which probe this driver have the interrupt provided from Device Tree, with no need to handle a case where the IRQ was not provided. Co-developed-by: Paul Cercueil <paul@crapouillou.net> Signed-off-by: Paul Cercueil <paul@crapouillou.net> Signed-off-by: Artur Rojek <contact@artur-rojek.eu> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.