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Mainline Linux tree for various devices, only for fun :)
09cdb237c3
As explained in chapter "NV-DDR / NV-DDR2 / NV-DDR3 and Repeat Bytes" of the ONFI specification, with some commands (mainly the commands which do not transfer actual data) the data bytes are repeated twice and it is the responsibility of the receiver to discard them properly. The concerned commands are: SET_FEATURES, READ_ID, GET_FEATURES, READ_STATUS, READ_STATUS_ENHANCED, ODT_CONFIGURE. Hence, in the NAND core we are only impacted by the implementation of READ_ID, GET_FEATURES and READ_STATUS. The logic is the same for all: 2/ Check if it is relevant to read all data bytes twice. 1/ Allocate a buffer with twice the requested size (may be done statically). 2/ Update the instruction structure to read these extra bytes in the allocated buffer. 3/ Copy the even bytes into the original buffer. The performance hit is negligible on such small data transfers anyway and we don't really care about performances at this stage anyway. 4/ Free the allocated buffer, if any. Note: nand_data_read_op() is also impacted because it is theoretically possible to run the command/address cycles first, and, as another operation, do the data transfers. In this case we can easily identify the impacted commands because the force_8bit flag will be set (due to the same reason: their data does not go through the same pipeline). Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Link: https://lore.kernel.org/linux-mtd/20210505213750.257417-15-miquel.raynal@bootlin.com |
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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.