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diff --git a/Documentation/hwmon/bt1-pvt.rst b/Documentation/hwmon/bt1-pvt.rst new file mode 100644 index 0000000000..cbb0c06131 --- /dev/null +++ b/Documentation/hwmon/bt1-pvt.rst @@ -0,0 +1,117 @@ +.. 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. +=============================== ======= ======================================= |