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Baikal-T1 SoC provides an embedded process, voltage and temperature sensor to monitor an internal SoC environment (chip temperature, supply voltage and process monitor) and on time detect critical situations, which may cause the system instability and even damages. The IP-block is based on the Analog Bits PVT sensor, but is equipped with a dedicated control wrapper, which provides a MMIO registers-based access to the sensor core functionality (APB3-bus based) and exposes an additional functions like thresholds/data ready interrupts, its status and masks, measurements timeout. All of these is used to create a hwmon driver being added to the kernel by this commit. The driver implements support for the hardware monitoring capabilities of Baikal-T1 process, voltage and temperature sensors. PVT IP-core consists of one temperature and four voltage sensors, each of which is implemented as a dedicated hwmon channel config. 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 limitations 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 this design may cause additional burden on the system performance. By default if the alarms kernel config is disabled the data conversion is performed by the driver on demand when read operation is requested via corresponding _input-file. Co-developed-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru> Signed-off-by: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Rob Herring <robh+dt@kernel.org> Cc: linux-mips@vger.kernel.org Cc: devicetree@vger.kernel.org Signed-off-by: Guenter Roeck <linux@roeck-us.net>
118 lines
4.9 KiB
ReStructuredText
118 lines
4.9 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0-only
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Kernel driver bt1-pvt
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=====================
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Supported chips:
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* Baikal-T1 PVT sensor (in SoC)
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Prefix: 'bt1-pvt'
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Addresses scanned: -
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Datasheet: Provided by BAIKAL ELECTRONICS upon request and under NDA
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Authors:
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Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru>
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Serge Semin <Sergey.Semin@baikalelectronics.ru>
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Description
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-----------
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This driver implements support for the hardware monitoring capabilities of the
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embedded into Baikal-T1 process, voltage and temperature sensors. PVT IP-core
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consists of one temperature and four voltage sensors, which can be used to
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monitor the chip internal environment like heating, supply voltage and
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transistors performance. The driver can optionally provide the hwmon alarms
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for each sensor the PVT controller supports. The alarms functionality is made
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compile-time configurable due to the hardware interface implementation
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peculiarity, which is connected with an ability to convert data from only one
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sensor at a time. Additional limitation is that the controller performs the
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thresholds checking synchronously with the data conversion procedure. Due to
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these in order to have the hwmon alarms automatically detected the driver code
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must switch from one sensor to another, read converted data and manually check
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the threshold status bits. Depending on the measurements timeout settings
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(update_interval sysfs node value) this design may cause additional burden on
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the system performance. So in case if alarms are unnecessary in your system
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design it's recommended to have them disabled to prevent the PVT IRQs being
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periodically raised to get the data cache/alarms status up to date. By default
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in alarm-less configuration the data conversion is performed by the driver
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on demand when read operation is requested via corresponding _input-file.
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Temperature Monitoring
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----------------------
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Temperature is measured with 10-bit resolution and reported in millidegree
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Celsius. The driver performs all the scaling by itself therefore reports true
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temperatures that don't need any user-space adjustments. While the data
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translation formulae isn't linear, which gives us non-linear discreteness,
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it's close to one, but giving a bit better accuracy for higher temperatures.
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The temperature input is mapped as follows (the last column indicates the input
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ranges)::
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temp1: CPU embedded diode -48.38C - +147.438C
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In case if the alarms kernel config is enabled in the driver the temperature input
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has associated min and max limits which trigger an alarm when crossed.
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Voltage Monitoring
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------------------
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The voltage inputs are also sampled with 10-bit resolution and reported in
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millivolts. But in this case the data translation formulae is linear, which
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provides a constant measurements discreteness. The data scaling is also
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performed by the driver, so returning true millivolts. The voltage inputs are
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mapped as follows (the last column indicates the input ranges)::
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in0: VDD (processor core) 0.62V - 1.168V
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in1: Low-Vt (low voltage threshold) 0.62V - 1.168V
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in2: High-Vt (high voltage threshold) 0.62V - 1.168V
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in3: Standard-Vt (standard voltage threshold) 0.62V - 1.168V
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In case if the alarms config is enabled in the driver the voltage inputs
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have associated min and max limits which trigger an alarm when crossed.
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Sysfs Attributes
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----------------
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Following is a list of all sysfs attributes that the driver provides, their
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permissions and a short description:
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=============================== ======= =======================================
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Name Perm Description
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=============================== ======= =======================================
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update_interval RW Measurements update interval per
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sensor.
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temp1_type RO Sensor type (always 1 as CPU embedded
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diode).
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temp1_label RO CPU Core Temperature sensor.
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temp1_input RO Measured temperature in millidegree
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Celsius.
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temp1_min RW Low limit for temp input.
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temp1_max RW High limit for temp input.
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temp1_min_alarm RO Temperature input alarm. Returns 1 if
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temperature input went below min limit,
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0 otherwise.
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temp1_max_alarm RO Temperature input alarm. Returns 1 if
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temperature input went above max limit,
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0 otherwise.
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temp1_offset RW Temperature offset in millidegree
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Celsius which is added to the
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temperature reading by the chip. It can
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be used to manually adjust the
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temperature measurements within 7.130
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degrees Celsius.
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in[0-3]_label RO CPU Voltage sensor (either core or
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low/high/standard thresholds).
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in[0-3]_input RO Measured voltage in millivolts.
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in[0-3]_min RW Low limit for voltage input.
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in[0-3]_max RW High limit for voltage input.
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in[0-3]_min_alarm RO Voltage input alarm. Returns 1 if
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voltage input went below min limit,
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0 otherwise.
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in[0-3]_max_alarm RO Voltage input alarm. Returns 1 if
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voltage input went above max limit,
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0 otherwise.
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=============================== ======= =======================================
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