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3d394f8541
The VPU is responsible for managing the core clock, usually under direction from the bcm2835-cpufreq driver but not via the clk-bcm2835 driver. Since the core frequency can change without warning, it is safer to report the maximum clock rate to users of the core clock - I2C, SPI and the mini UART - to err on the safe side when calculating clock divisors. If the DT node for the clock driver includes a reference to the firmware node, use the firmware API to query the maximum core clock instead of reading the divider registers. Prior to this patch, a "100KHz" I2C bus was sometimes clocked at about 160KHz. In particular, switching to the 4.9 kernel was likely to break SenseHAT usage on a Pi3. Signed-off-by: Phil Elwell <phil@raspberrypi.org>
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.