Mtd subsystem stands for memory technology devices provides an. Additionally, linux handles flash memory using the mtd modules. A generic subsystem for handling memory technology devices under linux. Bad block markers are either set at the factory during manufacture, or by software when it detects wear in.
Nor beside the different silicon cell design, the most important difference between nand and nor flash is the bus interface. Then you can use jffs2 or ubifs on nand as your root filesystem. Activate mtd in the kernel configuration with the linux menuconfig tool. Need to send write enablewren command before a write or erase.
Beside the different silicon cell design, the most important difference. It must be loaded into ram memory and executed from there. Contribute to torvaldslinux development by creating an account on github. Mtd provides such drivers to manage nandresident data. The purpose of this article is to introduce the mtd linux subsystem. Mtd does not contain any bad block handling or wear leveling routines, so the use of mtd alone is not recommended on nand flash media.
Besides file system on hard disk, flash file system in nor flash or nand flash are two options. Memory technology devices mtd edit edit source mtd subsystem memory technology devices provides an abstraction layer for raw flash devices. It makes it possible to use the same api when working with different flash types and technologies, e. This patch adds prefetch support to access nand flash in both mpu and dma mode. Nand flash chips, unlike nor chips, are not faultless. The generic nand driver supports 816 bit wide nand flash only. Nor flash was the first type of flash storage that was invented. Im trying to write on a nand flash memory using mtd block device but i dont understand everything. Understanding memory technology devices in embedded linux. Mtd,nand add prefetch and dma support for omap23 nand. The linux kernel implements a memory technology device mtd subsystem that allows.
How to configure the linux kerneldevice driversmemory. Instead, developers are asked to use a full flash file system on linux, such as yaffs, jffs2 and ubifs. Mtd nand driver programming interface the linux kernel. This requires to implement hardware or software solutions, called wear leveling. See the linuxmtd website for the most current information about. Nor flash is connected to a address data bus direct like other memory devices as sram etc. Nor flash can be used for code storage and code execution. The various methods by which a driver provides access to the device are. Nand flash is a sequential access device appropriate for mass storage applications, while nor flash is a random access device appropriate for code storage application. Unfortunately, neither the low level driver portions of mtd nor the commonly available flash file systems. Serial nor flash that is interfaced to soc via spi bus and follows spi protocol.
This option will provide the generic support for mtd drivers to register themselves with the kernel and for potential users of mtd devices to enumerate the devices which are present and obtain a handle on them. I work on supporting peripheral drivers on ti socs, mainly qspi, uart. An introduction to spinor subsystem linux foundation events. Code stored on nand flash cant be executed from there. Mtd subsystem stands for memory technology devices provides an abstraction layer for raw flash devices.
Once the simulator or a real flash driver is loaded, we can read procmtd to see the status of mtd. Nand flash is a sequential access device appropriate for mass storage. Memory technology devices are flash, ram and similar chips, often used for solid state file systems on embedded devices. Beside the different silicon cell design, the most important difference between nand and nor flash is the bus interface. It makes it possible to use the same api when working with different flash types and technologies nor and nand in particular. Please refer to the official documentation for detailed information. Nand memory technology device mtd subsystem for linux. This documentation is provided for developers who want to implement board drivers or filesystem drivers suitable for nand devices. As i read here mtdblockn is the read only block device n mtdn is the readwrite char device n. Nand flash uses a multiplexed io interface with some additional control pins. The write protect wp pin is only used for nand devices.