linux/drivers/mtd/Kconfig

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UBI: Unsorted Block Images UBI (Latin: "where?") manages multiple logical volumes on a single flash device, specifically supporting NAND flash devices. UBI provides a flexible partitioning concept which still allows for wear-levelling across the whole flash device. In a sense, UBI may be compared to the Logical Volume Manager (LVM). Whereas LVM maps logical sector numbers to physical HDD sector numbers, UBI maps logical eraseblocks to physical eraseblocks. More information may be found at http://www.linux-mtd.infradead.org/doc/ubi.html Partitioning/Re-partitioning An UBI volume occupies a certain number of erase blocks. This is limited by a configured maximum volume size, which could also be viewed as the partition size. Each individual UBI volume's size can be changed independently of the other UBI volumes, provided that the sum of all volume sizes doesn't exceed a certain limit. UBI supports dynamic volumes and static volumes. Static volumes are read-only and their contents are protected by CRC check sums. Bad eraseblocks handling UBI transparently handles bad eraseblocks. When a physical eraseblock becomes bad, it is substituted by a good physical eraseblock, and the user does not even notice this. Scrubbing On a NAND flash bit flips can occur on any write operation, sometimes also on read. If bit flips persist on the device, at first they can still be corrected by ECC, but once they accumulate, correction will become impossible. Thus it is best to actively scrub the affected eraseblock, by first copying it to a free eraseblock and then erasing the original. The UBI layer performs this type of scrubbing under the covers, transparently to the UBI volume users. Erase Counts UBI maintains an erase count header per eraseblock. This frees higher-level layers (like file systems) from doing this and allows for centralized erase count management instead. The erase counts are used by the wear-levelling algorithm in the UBI layer. The algorithm itself is exchangeable. Booting from NAND For booting directly from NAND flash the hardware must at least be capable of fetching and executing a small portion of the NAND flash. Some NAND flash controllers have this kind of support. They usually limit the window to a few kilobytes in erase block 0. This "initial program loader" (IPL) must then contain sufficient logic to load and execute the next boot phase. Due to bad eraseblocks, which may be randomly scattered over the flash device, it is problematic to store the "secondary program loader" (SPL) statically. Also, due to bit-flips it may become corrupted over time. UBI allows to solve this problem gracefully by storing the SPL in a small static UBI volume. UBI volumes vs. static partitions UBI volumes are still very similar to static MTD partitions: * both consist of eraseblocks (logical eraseblocks in case of UBI volumes, and physical eraseblocks in case of static partitions; * both support three basic operations - read, write, erase. But UBI volumes have the following advantages over traditional static MTD partitions: * there are no eraseblock wear-leveling constraints in case of UBI volumes, so the user should not care about this; * there are no bit-flips and bad eraseblocks in case of UBI volumes. So, UBI volumes may be considered as flash devices with relaxed restrictions. Where can it be found? Documentation, kernel code and applications can be found in the MTD gits. What are the applications for? The applications help to create binary flash images for two purposes: pfi files (partial flash images) for in-system update of UBI volumes, and plain binary images, with or without OOB data in case of NAND, for a manufacturing step. Furthermore some tools are/and will be created that allow flash content analysis after a system has crashed.. Who did UBI? The original ideas, where UBI is based on, were developed by Andreas Arnez, Frank Haverkamp and Thomas Gleixner. Josh W. Boyer and some others were involved too. The implementation of the kernel layer was done by Artem B. Bityutskiy. The user-space applications and tools were written by Oliver Lohmann with contributions from Frank Haverkamp, Andreas Arnez, and Artem. Joern Engel contributed a patch which modifies JFFS2 so that it can be run on a UBI volume. Thomas Gleixner did modifications to the NAND layer. Alexander Schmidt made some testing work as well as core functionality improvements. Signed-off-by: Artem B. Bityutskiy <dedekind@linutronix.de> Signed-off-by: Frank Haverkamp <haver@vnet.ibm.com>
2006-06-27 12:22:22 +04:00
mtd: Add support for HyperBus memory devices Cypress' HyperBus is Low Signal Count, High Performance Double Data Rate Bus interface between a host system master and one or more slave interfaces. HyperBus is used to connect microprocessor, microcontroller, or ASIC devices with random access NOR flash memory (called HyperFlash) or self refresh DRAM (called HyperRAM). Its a 8-bit data bus (DQ[7:0]) with Read-Write Data Strobe (RWDS) signal and either Single-ended clock(3.0V parts) or Differential clock (1.8V parts). It uses ChipSelect lines to select b/w multiple slaves. At bus level, it follows a separate protocol described in HyperBus specification[1]. HyperFlash follows CFI AMD/Fujitsu Extended Command Set (0x0002) similar to that of existing parallel NORs. Since HyperBus is x8 DDR bus, its equivalent to x16 parallel NOR flash with respect to bits per clock cycle. But HyperBus operates at >166MHz frequencies. HyperRAM provides direct random read/write access to flash memory array. But, HyperBus memory controllers seem to abstract implementation details and expose a simple MMIO interface to access connected flash. Add support for registering HyperFlash devices with MTD framework. MTD maps framework along with CFI chip support framework are used to support communicating with flash. Framework is modelled along the lines of spi-nor framework. HyperBus memory controller (HBMC) drivers calls hyperbus_register_device() to register a single HyperFlash device. HyperFlash core parses MMIO access information from DT, sets up the map_info struct, probes CFI flash and registers it with MTD framework. Some HBMC masters need calibration/training sequence[3] to be carried out, in order for DLL inside the controller to lock, by reading a known string/pattern. This is done by repeatedly reading CFI Query Identification String. Calibration needs to be done before trying to detect flash as part of CFI flash probe. HyperRAM is not supported at the moment. HyperBus specification can be found at[1] HyperFlash datasheet can be found at[2] [1] https://www.cypress.com/file/213356/download [2] https://www.cypress.com/file/213346/download [3] http://www.ti.com/lit/ug/spruid7b/spruid7b.pdf Table 12-5741. HyperFlash Access Sequence Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
2019-06-25 13:27:44 +05:30