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During a short period when the bus voltage is switched from 3.3v to 1.8v, (to enumerate UHS mode), the mmc module is disabled and the mmc IO lines are kept in a state according to the programmed pad mux pull type. According to 4.2.4.2 Timing to Switch Signal Voltage in "SD Specifications Part 1 Physical Layer Specification Version 5.00 February 22, 2016", the host should hold CLK low for at least 5ms. In order to keep the card line low during voltage switch, the pad mux of mmc1_clk line should be configured to pull down. Add a new pinctrl group for clock line without pullup to be used in boards where mmc1_clk line is not connected to an external pullup. Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com> Signed-off-by: Tony Lindgren <tony@atomide.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.
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.