Alex Zhao b59b1c0040 mmc: add a file to debugfs for changing host max clock at runtime
Usage is as follows:

rk3566_rgo:/ # cat /sys/kernel/debug/mmc1/max_clock
150000000

rk3566_rgo:/ # echo 200000000 > /sys/kernel/debug/mmc1/max_clock
rk3566_rgo:/ # cat /sys/kernel/debug/mmc1/max_clock
200000000
rk3566_rgo:/ # echo 200000000 >  /sys/kernel/debug/mmc1/clock

rk3566_rgo:/ # dmesg -c
[  285.884348] mmc_host mmc1: Bus speed (slot 0) = 198000000Hz (slot req 200000000Hz, actual 198000000HZ div = 0)

Signed-off-by: Alex Zhao <zzc@rock-chips.com>
Change-Id: I7ac9649b231c50b0c6c066407e28954e8c94510c
2021-01-06 15:18:42 +08:00

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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.
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