Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 90 insertions, 0 deletions

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+Kernel driver lm73
+==================
+
+Supported chips:
+  * Texas Instruments LM73
+    Prefix: 'lm73'
+    Addresses scanned: I2C 0x48, 0x49, 0x4a, 0x4c, 0x4d, and 0x4e
+    Datasheet: Publicly available at the Texas Instruments website
+               http://www.ti.com/product/lm73
+
+Author: Guillaume Ligneul <guillaume.ligneul@gmail.com>
+Documentation: Chris Verges <kg4ysn@gmail.com>
+
+
+Description
+-----------
+
+The LM73 is a digital temperature sensor.  All temperature values are
+given in degrees Celsius.
+
+Measurement Resolution Support
+------------------------------
+
+The LM73 supports four resolutions, defined in terms of degrees C per
+LSB: 0.25, 0.125, 0.0625, and 0.3125.  Changing the resolution mode
+affects the conversion time of the LM73's analog-to-digital converter.
+From userspace, the desired resolution can be specified as a function of
+conversion time via the 'update_interval' sysfs attribute for the
+device.  This attribute will normalize ranges of input values to the
+maximum times defined for the resolution in the datasheet.
+
+    Resolution    Conv. Time    Input Range
+    (C/LSB)       (msec)        (msec)
+    --------------------------------------
+    0.25          14             0..14
+    0.125         28            15..28
+    0.0625        56            29..56
+    0.03125       112           57..infinity
+    --------------------------------------
+
+The following examples show how the 'update_interval' attribute can be
+used to change the conversion time:
+
+    $ echo 0 > update_interval
+    $ cat update_interval
+    14
+    $ cat temp1_input
+    24250
+
+    $ echo 22 > update_interval
+    $ cat update_interval
+    28
+    $ cat temp1_input
+    24125
+
+    $ echo 56 > update_interval
+    $ cat update_interval
+    56
+    $ cat temp1_input
+    24062
+
+    $ echo 85 > update_interval
+    $ cat update_interval
+    112
+    $ cat temp1_input
+    24031
+
+As shown here, the lm73 driver automatically adjusts any user input for
+'update_interval' via a step function.  Reading back the
+'update_interval' value after a write operation will confirm the
+conversion time actively in use.
+
+Mathematically, the resolution can be derived from the conversion time
+via the following function:
+
+   g(x) = 0.250 * [log(x/14) / log(2)]
+
+where 'x' is the output from 'update_interval' and 'g(x)' is the
+resolution in degrees C per LSB.
+
+Alarm Support
+-------------
+
+The LM73 features a simple over-temperature alarm mechanism.  This
+feature is exposed via the sysfs attributes.
+
+The attributes 'temp1_max_alarm' and 'temp1_min_alarm' are flags
+provided by the LM73 that indicate whether the measured temperature has
+passed the 'temp1_max' and 'temp1_min' thresholds, respectively.  These
+values _must_ be read to clear the registers on the LM73.