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Universal Serial Interface (USI) supports three types of serial interface such as Universal Asynchronous Receiver and Transmitter (UART), Serial Peripheral Interface (SPI), and Inter-Integrated Circuit (I2C). Each protocols can be working independently and configured as one of those using external configuration inputs. Exynos Auto v9 SoC support 12 USIs. When a USI uses two pins such as i2c and 3 wire uarts(RX/TX only), we can use remain two pins as i2c mode. So, we can define one USI node that includes serial/spi and hsi2c. usi_i2c nodes can be used only for i2c mode. We can have below combinations for one USI. 1) The usi node is used either 4 pin uart or 4 pin spi -> No usi_i2c can be used 2) The usi node is used 2 pin uart(RX/TX) and i2c(SDA/SCL) -> usi_i2c should be enabled to use the latter i2c 3) The usi node is used i2c(SDA/SCL) and i2c(SDA/SCL) -> usi_i2c should be enabled to use the latter i2c By default, all USIs are initially set to uart mode by below setting. samsung,mode = <USI_V2_UART>; You can change it either USI_V2_SPI or USI_V2_I2C. Signed-off-by: Chanho Park <chanho61.park@samsung.com> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Link: https://lore.kernel.org/r/20220701015226.32781-6-chanho61.park@samsung.com
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
``make pdfdocs``. The formatted documentation can also be read online at:
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.