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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.