4f38ae221e
Merge series from Sam Protsenko <semen.protsenko@linaro.org>:
This series enables SPI for Exynos850 SoC, there are also some
dependencies that will be needed at runtime which were sent as part of
the same series but will be separately applied:
1. Enable PDMA, it's needed for SPI (dts, clk)
2. Propagate SPI src clock rate change up to DIV clocks, to make it
possible to change SPI frequency (clk driver)
4. Add SPI nodes to Exynos850 SoC dtsi
All SPI instances were tested using `spidev_test' tool in all 3 possible
modes:
- Polling mode: xfer_size <= 32
- IRQ mode: 64 >= xfer_size >= 32
- DMA mode: xfer_size > 64
with 200 kHz ... 49.9 MHz SPI frequencies. The next 3 approaches were
used:
1. Software loopback ('-l' option for `spidev_test' tool)
2. Hardware loopback (by connecting MISO line to MOSI)
3. By communicating with ATMega found on Sensors Mezzanine board [1],
programmed to act as an SPI device
and all the transactions were additionally checked on my Logic Analyzer
to make sure the SCK frequencies were actually correct.
[1] https://www.96boards.org/product/sensors-mezzanine/
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.