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108d9dd513
According to John Crispin (aka blogic) on IRC on Nov 26 2018:
so basically i made cs1 work for MTK/labs when i built
the linkit smart for them. the req-sheet said that cs1 should be proper
duplex spi. however ....
1) the core will always send 1 byte before any transfer, this is the
m25p80 command.
2) mode 3 is broken and bit reversed (?)
3) some bit are incorrectly wired in hw for mode2/3
we wrote a test script and test for [0-0xffff] on all modes and certain
bits are swizzled under certain conditions and it was not possible to
fix this even using a hack.
we then decided to use spi-gpio and i never removed the errornous code
basically the spi is fecked for anything but half duplex spi mode0
running a sflash on it
The controller will always send some data from OPCODE register under half
duplex mode before starting a full-duplex transfer, so the full-duplex
mode is broken.
This piece of code also make CS1 unavailable since it forces the
broken full-duplex mode to be used on CS1.
Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.