iio: adc: tsc2046: silent spi_device_id warning

Add spi_device_id to silent following kernel runtime warning:
"SPI driver tsc2046 has no spi_device_id for ti,tsc2046e-adc".

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220904100203.3614502-3-o.rempel@pengutronix.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: tsc2046: add vref support

If VREF pin is attached, we should use external VREF source instead of
the internal. Otherwise we will get wrong measurements on some of the channel
types.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220904100203.3614502-2-o.rempel@pengutronix.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: ti-tsc2046: do not explicity set INDIO_BUFFER_TRIGGERED mode

The core sets INDIO_BUFFER_TRIGGERED as part of
devm_iio_triggered_buffer_setup().

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20220629203910.4836-1-marcus.folkesson@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: tsc2046: add sanity check to avoid to big allocations

To avoid problematic devicetree configurations. Set allocation limit
with error message and suggestion on what can be done to solve this
issue.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20220117082852.3370869-2-o.rempel@pengutronix.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: tsc2046: add .read_raw support

Add read_raw() support to make use of iio_hwmon and other iio clients.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20220117082852.3370869-1-o.rempel@pengutronix.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: tsc2046: rework the trigger state machine

Initially this was designed to:
| Fix sleeping in atomic context warning and a deadlock after iio_trigger_poll()
| call
|
| If iio_trigger_poll() is called after IRQ was disabled, we will call
| reenable_trigger() directly from hard IRQ or hrtimer context instead of
| IRQ thread. In this case we will run in to multiple issue as sleeping in atomic
| context and a deadlock.
|
| To avoid this issue, rework the trigger to use state machine. All state
| changes are done over the hrtimer, so it allows us to drop fsleep() and
| avoid the deadlock.

Since this issue was fixed by: 9020ef659885 ("iio: trigger: Fix a scheduling
whilst atomic issue seen on tsc2046"). This patch is a cleanup to make
state machine easier to follow.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20220111130402.3404769-1-o.rempel@pengutronix.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: tsc2046: fix memory corruption by preventing array overflow

On one side we have indio_dev->num_channels includes all physical channels +
timestamp channel. On other side we have an array allocated only for
physical channels. So, fix memory corruption by ARRAY_SIZE() instead of
num_channels variable.

Note the first case is a cleanup rather than a fix as the software
timestamp channel bit in active_scanmask is never set by the IIO core.

Fixes: 9374e8f5a38d ("iio: adc: add ADC driver for the TI TSC2046 controller")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20220107081401.2816357-1-o.rempel@pengutronix.de
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: tsc2046: fix scan interval warning

Sync if statement with the actual warning.

Fixes: 9504db5765e8 ("iio: adc: tsc2046: fix a warning message in tsc2046_adc_update_scan_mode()")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20211007093007.1466-2-o.rempel@pengutronix.de
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: remove unused private data assigned with spi_set_drvdata()

These were usually used before the conversion to devm_ functions, so that
the remove hook would be able to retrieve the pointer and do cleanups on
remove.
When the conversion happened, they should have been removed, but were
omitted.

Some drivers were copied from drivers that fit the criteria described
above. In any case, in order to prevent more drivers from being used as
example (and have spi_set_drvdata() needlessly set), this change removes it
from the IIO ADC group.

Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210513111035.77950-1-aardelean@deviqon.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: tsc2046: fix a warning message in tsc2046_adc_update_scan_mode()

These variables are unsigned so the condition can't be less than zero
and the warning message will never be printed.

Fixes: 9374e8f5a38d ("iio: adc: add ADC driver for the TI TSC2046 controller")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YJ+ZuO43TnguY5vq@mwanda
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: adc: add ADC driver for the TI TSC2046 controller

Basically the TI TSC2046 touchscreen controller is 8 channel ADC optimized for
the touchscreen use case. By implementing it as an IIO ADC device, we can
make use of resistive-adc-touch and iio-hwmon drivers.

Polled readings are currently not implemented to keep this patch small, so
iio-hwmon will not work out of the box for now.

So far, this driver was tested with a custom version of resistive-adc-touch driver,
since it needs to be extended to make use of Z1 and Z2 channels. The X/Y
are working without additional changes.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210428073208.19570-4-o.rempel@pengutronix.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>