iio: humidity: dht11: Switch from of headers to mod_devicetable.h

There is nothing directly using of specific interfaces in this driver,
so lets not include the headers.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220202203420.56654-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: remove left-over parent assignments

These were found by doing some shell magic:
------------
for file in $(git grep -w devm_iio_device_alloc | cut -d: -f1 | sort | uniq) ; do
if grep 'parent =' $file | grep -v trig | grep -vq devm_; then
echo "$file -> $(grep "parent =" $file)"
fi
done
-----------

The output is bearable [after the semantic patch is applied].
There is a mix of trigger assignments with some iio device parent
assignments that are removed via this patch.

JC: A few more added via inspection of all parent =
statements in drivers/iio. Some of these may just have crossed with this
series, others were less obvious to scripting due to some cross
file / module boundary calls.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: humidity: dht11 remove TODO since it doesn't make sense

DHT11 isn't addressable and will trigger temperature measurement on any
data sent on the bus.

Signed-off-by: Kent Gustavsson <kent@minoris.se>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

timekeeping: Use proper clock specifier names in functions

This makes boot uniformly boottime and tai uniformly clocktai, to
address the remaining oversights.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lkml.kernel.org/r/20190621203249.3909-2-Jason@zx2c4.com

iio: humidity: Replace older GPIO APIs with GPIO Consumer APIs for the dht11 sensor

The dht11 driver uses a single gpio to make measurements. It was
using the older global gpio numberspace. The patch replaces the
old gpio api with the new gpio descriptor based api.

Removed header files "linux/gpio.h" and "linux/of_gpio.h"

Signed-off-by: Shobhit Kukreti <shobhitkukreti@gmail.com>
Acked-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157

Based on 3 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version [author] [kishon] [vijay] [abraham]
[i] [kishon]@[ti] [com] this program is distributed in the hope that
it will be useful but without any warranty without even the implied
warranty of merchantability or fitness for a particular purpose see
the gnu general public license for more details

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version [author] [graeme] [gregory]
[gg]@[slimlogic] [co] [uk] [author] [kishon] [vijay] [abraham] [i]
[kishon]@[ti] [com] [based] [on] [twl6030]_[usb] [c] [author] [hema]
[hk] [hemahk]@[ti] [com] this program is distributed in the hope
that it will be useful but without any warranty without even the
implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 1105 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.202006027@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

iio: dht11: Improve detection of sensor type

The old code was based on a DHT11 datasheet which specifies a measurement
range of 20%-90% RH. Turns out the sensor actually reports values outside
this range, so we should support it as far as possible.

Reported-by: Edward Attfield <edward@attfield.ca>
Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio:humidity: drop assign iio_info.driver_module and iio_trigger_ops.owner

The equivalent of both of these are now done via macro magic when
the relevant register calls are made. The actual structure
elements will shortly go away.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>

iio: dht11: Use usleep_range instead of msleep for start signal

The DHT22 (AM2302) datasheet specifies that the LOW start pulse should not
exceed 20ms. However, observations with an oscilloscope of an RPi Model 2B
(rev 1.1) communicating with a DHT22 sensor showed that the driver was
consistently sending start pulses longer than 20ms:

Kernel 4.7.10-v7+ (n=132):
Minimum pulse length: 20.20ms
Maximum: 29.84ms
Mean: 24.96ms
StDev: 2.82ms
Sensor response rate: 100%
Read success rate: 76%

On kernel 4.8, the start pulse was so long that the sensor would not even
respond 97% of the time:

Kernel 4.8.16-v7+ (n=100):
Minimum pulse length: 30.4ms
Maximum: 74.4ms
Mean: 39.3ms
StDev: 10.2ms
Sensor response rate: 3%
Read success rate: 3%

The driver would return ETIMEDOUT and write log messages like this:

[ 51.430987] dht11 dht11@0: Only 1 signal edges detected
[ 66.311019] dht11 dht11@0: Only 0 signal edges detected

Replacing msleep(18) with usleep_range(18000, 20000) made the pulse length
sane again and restored responsiveness:

Kernel 4.8.16-v7+ with usleep_range (n=123):
Minimum pulse length: 18.16ms
Maximum: 20.20ms
Mean: 19.85ms
StDev: 0.51ms
Sensor response rate: 100%
Read success rate: 84%

Cc: stable@vger.kernel.org
Signed-off-by: John Brooks <john@fastquake.com>
Reviewed-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: Improve logging

* Unify log messages
* Add more DEBUG messages

Apparently this driver is working unreliably on some platforms that I can't
test. Therefore I want an easy way for bug reporters to provide useful
information without making the driver too chatty by default.

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: Use boottime

Wall time obtained from ktime_get_real_ns is susceptible to sudden jumps due to
user setting the time or due to NTP. Boot time is constantly increasing time
better suited for comparing two timestamps.

Signed-off-by: Abhilash Jindal <klock.android@gmail.com>
Reviewed-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: Simplify decoding algorithm

The new algorithm uses a 'one size fits em all' threshold, which should
be easier to understand and debug. I believe there are no regressions
compared to the old adaptive threshold algorithm. I don't remember why
I chose the old algorithm when I initially wrote the driver.

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: Improve reliability - be more tolerant about missing start bits

Instead of guessing where the data starts, we now just try to decode from
every possible start position. This causes no additional overhead if we
properly received the full preamble and only costs a few extra CPU cycles
in the case where the preamble is corrupted. This is much more efficient
than to return an error to userspace and start over again.

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: Use new function ktime_get_resolution_ns()

This cleans up the most ugly workaround in this driver. There are no
functional changes yet in the decoding algorithm, but we improve the
following things:
* Get rid of spurious warning messages on systems with fast HRTIMER.
* If the clock is not fast enough for decoding to work, we give
up immediately.
* In that case we return EAGAIN instead of EIO, so it's easier to
discriminate causes of failure.

Returning EAGAIN is somewhat controversial: It's technically correct
as a faster clock might become available. OTOH once all clocks are
enabled this is a permanent error. There is no ECLOCKTOOSLOW error
code.

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: avoid multiple assignments to make checkpatch.pl --strict happy

We just do the assignments in two steps.

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: add comment to make checkpatch.pl --strict happy

Explain why the driver needs a mutex.

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: whitespace changes to make checkpatch.pl --strict happy

* add spaces around binary operators in cases where it reduces readability
* align multiline statements around opening parenthesis

Reported-by: Hartmut Knaack <knaack.h@gmx.de>
in Message-ID: <55919E72.3010807@gmx.de>

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: IRQ fixes

Since setting irq-enabled GPIOs into output state is not supported
by all GPIO controllers, we need to disable the irq while requesting
sensor data. As side effect we lose a tiny bit of functionality:
Some wiring problems can't be concluded from log messages anymore.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: Add locking

Make sure that the read function is not interrupted...

Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Harald Geyer <harald@ccbib.org>
Reviewed-by: Sanjeev Sharma <sanjeev_sharma@mentor.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: dht11: Fix out-of-bounds read

As we access i-1 we must not start with i=0.

Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Hartmut Knaack <knaack.h@gmx.de>
Acked-by: Harald Geyer <harald@ccbib.org>
Reviewed-by: Sanjeev Sharma <sanjeev_sharma@mentor.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: remove .owner field for driver using module_platform_driver

This patch removes the .owner field for drivers which use the
platform_driver_register api because this is overriden in
_platform_driver_register.

Signed-off-by: Sanjeev Sharma <Sanjeev_Sharma@mentor.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

iio: Add new driver dht11

This driver handles DHT11 and DHT22 sensors.

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>