Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+Kernel driver adt7475
+=====================
+
+Supported chips:
+  * Analog Devices ADT7473
+    Prefix: 'adt7473'
+    Addresses scanned: I2C 0x2C, 0x2D, 0x2E
+    Datasheet: Publicly available at the On Semiconductors website
+  * Analog Devices ADT7475
+    Prefix: 'adt7475'
+    Addresses scanned: I2C 0x2E
+    Datasheet: Publicly available at the On Semiconductors website
+  * Analog Devices ADT7476
+    Prefix: 'adt7476'
+    Addresses scanned: I2C 0x2C, 0x2D, 0x2E
+    Datasheet: Publicly available at the On Semiconductors website
+  * Analog Devices ADT7490
+    Prefix: 'adt7490'
+    Addresses scanned: I2C 0x2C, 0x2D, 0x2E
+    Datasheet: Publicly available at the On Semiconductors website
+
+Authors:
+	Jordan Crouse
+	Hans de Goede
+	Darrick J. Wong (documentation)
+	Jean Delvare
+
+
+Description
+-----------
+
+This driver implements support for the Analog Devices ADT7473, ADT7475,
+ADT7476 and ADT7490 chip family. The ADT7473 and ADT7475 differ only in
+minor details. The ADT7476 has additional features, including extra voltage
+measurement inputs and VID support. The ADT7490 also has additional
+features, including extra voltage measurement inputs and PECI support. All
+the supported chips will be collectively designed by the name "ADT747x" in
+the rest of this document.
+
+The ADT747x uses the 2-wire interface compatible with the SMBus 2.0
+specification. Using an analog to digital converter it measures three (3)
+temperatures and two (2) or more voltages. It has four (4) 16-bit counters
+for measuring fan speed. There are three (3) PWM outputs that can be used
+to control fan speed.
+
+A sophisticated control system for the PWM outputs is designed into the
+ADT747x that allows fan speed to be adjusted automatically based on any of the
+three temperature sensors. Each PWM output is individually adjustable and
+programmable. Once configured, the ADT747x will adjust the PWM outputs in
+response to the measured temperatures without further host intervention.
+This feature can also be disabled for manual control of the PWM's.
+
+Each of the measured inputs (voltage, temperature, fan speed) has
+corresponding high/low limit values. The ADT747x will signal an ALARM if
+any measured value exceeds either limit.
+
+The ADT747x samples all inputs continuously. The driver will not read
+the registers more often than once every other second. Further,
+configuration data is only read once per minute.
+
+Chip Differences Summary
+------------------------
+
+ADT7473:
+  * 2 voltage inputs
+  * system acoustics optimizations (not implemented)
+
+ADT7475:
+  * 2 voltage inputs
+
+ADT7476:
+  * 5 voltage inputs
+  * VID support
+
+ADT7490:
+  * 6 voltage inputs
+  * 1 Imon input (not implemented)
+  * PECI support (not implemented)
+  * 2 GPIO pins (not implemented)
+  * system acoustics optimizations (not implemented)
+
+Special Features
+----------------
+
+The ADT747x has a 10-bit ADC and can therefore measure temperatures
+with a resolution of 0.25 degree Celsius. Temperature readings can be
+configured either for two's complement format or "Offset 64" format,
+wherein 64 is subtracted from the raw value to get the temperature value.
+
+The datasheet is very detailed and describes a procedure for determining
+an optimal configuration for the automatic PWM control.
+
+Fan Speed Control
+-----------------
+
+The driver exposes two trip points per PWM channel.
+
+point1: Set the PWM speed at the lower temperature bound
+point2: Set the PWM speed at the higher temperature bound
+
+The ADT747x will scale the PWM linearly between the lower and higher PWM
+speed when the temperature is between the two temperature boundaries.
+Temperature boundaries are associated to temperature channels rather than
+PWM outputs, and a given PWM output can be controlled by several temperature
+channels. As a result, the ADT747x may compute more than one PWM value
+for a channel at a given time, in which case the maximum value (fastest
+fan speed) is applied. PWM values range from 0 (off) to 255 (full speed).
+
+Fan speed may be set to maximum when the temperature sensor associated with
+the PWM control exceeds temp#_max.
+
+At Tmin - hysteresis the PWM output can either be off (0% duty cycle) or at the
+minimum (i.e. auto_point1_pwm). This behaviour can be configured using the
+pwm[1-*]_stall_disable sysfs attribute. A value of 0 means the fans will shut
+off. A value of 1 means the fans will run at auto_point1_pwm.
+
+The responsiveness of the ADT747x to temperature changes can be configured.
+This allows smoothing of the fan speed transition. To set the transition time
+set the value in ms in the temp[1-*]_smoothing sysfs attribute.
+
+Notes
+-----
+
+The nVidia binary driver presents an ADT7473 chip via an on-card i2c bus.
+Unfortunately, they fail to set the i2c adapter class, so this driver may
+fail to find the chip until the nvidia driver is patched.