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Now that the core NAND subsystem has support for on-die ECC, this commit brings the necessary code to support on-die ECC on Micron NANDs. In micron_nand_init(), we detect if the Micron NAND chip supports on-die ECC mode, by checking a number of conditions: - It must be an ONFI NAND - It must be a SLC NAND - Enabling *and* disabling on-die ECC must work - The on-die ECC must be correcting 4 bits per 512 bytes of data. Some Micron NAND chips have an on-die ECC able to correct 8 bits per 512 bytes of data, but they work slightly differently and therefore we don't support them in this patch. Then, if the on-die ECC cannot be disabled (some Micron NAND have on-die ECC forcefully enabled), we bail out, as we don't support such NANDs. Indeed, the implementation of raw_read()/raw_write() make the assumption that on-die ECC can be disabled. Support for Micron NANDs with on-die ECC forcefully enabled can easily be added, but in the absence of such HW for testing, we preferred to simply bail out. If the on-die ECC is supported, and requested in the Device Tree, then it is indeed enabled, by using custom implementations of the ->read_page(), ->read_page_raw(), ->write_page() and ->write_page_raw() operation to properly handle the on-die ECC. In the non-raw functions, we need to enable the internal ECC engine before issuing the NAND_CMD_READ0 or NAND_CMD_SEQIN commands, which is why we set the NAND_ECC_CUSTOM_PAGE_ACCESS option at initialization time (it asks the NAND core to let the NAND driver issue those commands). Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.