Linux kernel drivers for I2C-manageable high precision power source based on ISL22317 and PCA9536 chips

Within the bounds of verification test bench development for multicore Elbrus microprocessor ZAO MCST [1] designed precision single I
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C-controlled power source based on Intersil ISL22317 digital control potentiometer and NXP PCA9536 4-bit SMBus I/O port chip. Power source was built on four potentiomenters and one SMBus I/O port. Linux kernel driver for ISL22317, implemented by the authors, allowed to support software-manageable power supply for test microprocessor and to select a set of optimal supply voltages for test microprocessor cores precisely. As the solution has been admitted to be useful for developers, it was decided to contribute implemented driver of ISL22317 to Linux kernel community. Suggested driver implementation is universal and it can turn to be useful for other hardware devices built on ISL22317. Current article contains a generalized scheme of power source, description of ISL22317 driver's sysfs interfaces. The article reports on the suggested algorithm of voltage supply management from userspace programms. Much attention is payed to details of potentiometer driver implementaion. Readers attention is drawn to the driver initialization and device instantiating methods for ISL22317 and peculiarities of interaction between potentiometers and PCA9536 chip. Suggested software support makes possible to manage up to four potentiometers bound to common I
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C bus. Article also informs on algorithm of management up to 4 power sources bound to the same I
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C bus. Proposed algorithm is based on I
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C-bus multiplexing by Linear LTC4306 chip. The source code of Linux kernel driver of LTC4306 multiplexer, imlemented by authors, is covered by GNU General Public License version 2 and is available in public git repository along with ISL22317 driver. Current article reports on project in progress. In the conclusion authors carry out drawbacks analyze of suggested power source design and propose a simplified variant of I
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C-manageable power source implementaion based on a single chip.