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+.. SPDX-License-Identifier: GPL-2.0-only
+
+Kernel driver bt1-pvt
+=====================
+
+Supported chips:
+
+ * Baikal-T1 PVT sensor (in SoC)
+
+ Prefix: 'bt1-pvt'
+
+ Addresses scanned: -
+
+ Datasheet: Provided by BAIKAL ELECTRONICS upon request and under NDA
+
+Authors:
+ Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
+ Serge Semin <Sergey.Semin@baikalelectronics.ru>
+
+Description
+-----------
+
+This driver implements support for the hardware monitoring capabilities of the
+embedded into Baikal-T1 process, voltage and temperature sensors. PVT IP-core
+consists of one temperature and four voltage sensors, which can be used to
+monitor the chip internal environment like heating, supply voltage and
+transistors performance. The driver can optionally provide the hwmon alarms
+for each sensor the PVT controller supports. The alarms functionality is made
+compile-time configurable due to the hardware interface implementation
+peculiarity, which is connected with an ability to convert data from only one
+sensor at a time. Additional limitation is that the controller performs the
+thresholds checking synchronously with the data conversion procedure. Due to
+these in order to have the hwmon alarms automatically detected the driver code
+must switch from one sensor to another, read converted data and manually check
+the threshold status bits. Depending on the measurements timeout settings
+(update_interval sysfs node value) this design may cause additional burden on
+the system performance. So in case if alarms are unnecessary in your system
+design it's recommended to have them disabled to prevent the PVT IRQs being
+periodically raised to get the data cache/alarms status up to date. By default
+in alarm-less configuration the data conversion is performed by the driver
+on demand when read operation is requested via corresponding _input-file.
+
+Temperature Monitoring
+----------------------
+
+Temperature is measured with 10-bit resolution and reported in millidegree
+Celsius. The driver performs all the scaling by itself therefore reports true
+temperatures that don't need any user-space adjustments. While the data
+translation formulae isn't linear, which gives us non-linear discreteness,
+it's close to one, but giving a bit better accuracy for higher temperatures.
+The temperature input is mapped as follows (the last column indicates the input
+ranges)::
+
+ temp1: CPU embedded diode -48.38C - +147.438C
+
+In case if the alarms kernel config is enabled in the driver the temperature input
+has associated min and max limits which trigger an alarm when crossed.
+
+Voltage Monitoring
+------------------
+
+The voltage inputs are also sampled with 10-bit resolution and reported in
+millivolts. But in this case the data translation formulae is linear, which
+provides a constant measurements discreteness. The data scaling is also
+performed by the driver, so returning true millivolts. The voltage inputs are
+mapped as follows (the last column indicates the input ranges)::
+
+ in0: VDD (processor core) 0.62V - 1.168V
+ in1: Low-Vt (low voltage threshold) 0.62V - 1.168V
+ in2: High-Vt (high voltage threshold) 0.62V - 1.168V
+ in3: Standard-Vt (standard voltage threshold) 0.62V - 1.168V
+
+In case if the alarms config is enabled in the driver the voltage inputs
+have associated min and max limits which trigger an alarm when crossed.
+
+Sysfs Attributes
+----------------
+
+Following is a list of all sysfs attributes that the driver provides, their
+permissions and a short description:
+
+=============================== ======= =======================================
+Name Perm Description
+=============================== ======= =======================================
+update_interval RW Measurements update interval per
+ sensor.
+temp1_type RO Sensor type (always 1 as CPU embedded
+ diode).
+temp1_label RO CPU Core Temperature sensor.
+temp1_input RO Measured temperature in millidegree
+ Celsius.
+temp1_min RW Low limit for temp input.
+temp1_max RW High limit for temp input.
+temp1_min_alarm RO Temperature input alarm. Returns 1 if
+ temperature input went below min limit,
+ 0 otherwise.
+temp1_max_alarm RO Temperature input alarm. Returns 1 if
+ temperature input went above max limit,
+ 0 otherwise.
+temp1_offset RW Temperature offset in millidegree
+ Celsius which is added to the
+ temperature reading by the chip. It can
+ be used to manually adjust the
+ temperature measurements within 7.130
+ degrees Celsius.
+in[0-3]_label RO CPU Voltage sensor (either core or
+ low/high/standard thresholds).
+in[0-3]_input RO Measured voltage in millivolts.
+in[0-3]_min RW Low limit for voltage input.
+in[0-3]_max RW High limit for voltage input.
+in[0-3]_min_alarm RO Voltage input alarm. Returns 1 if
+ voltage input went below min limit,
+ 0 otherwise.
+in[0-3]_max_alarm RO Voltage input alarm. Returns 1 if
+ voltage input went above max limit,
+ 0 otherwise.
+=============================== ======= =======================================