MTD overview

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SUMMARY
MTD（内存技术设备）子系统为原始闪存提供抽象层。 在使用不同的Flash类型和技术（例如，Flash）时，可以使用相同的API。 SLC NAND，SPI NOR，...

Framework purpose

本文的目的是介绍MTD Linux子系统：

  • 一般信息
  • 主要组成部分/利益相关者
  • 如何使用MTD API

System overview

For ecosystem release ≥ v1.1.0{{#set:Ecosystem release=revision of a previous flow 1.1.0}}

MTD v1.1.0.png

For ecosystem release v1.0.0{{#set:Ecosystem release=revision of a previous flow 1.0.0}}

文件:Mtd.png

Component description

  • 执行“文件I / O”的用户空间应用程序需要像对待磁盘一样查看闪存，而希望完成“原始I / O”的程序就像访问磁盘一样访问该存储器。 是一个角色设备。
  • VFS (内核空间)

虚拟文件系统。 请参考VFS文档 [1].

  • mtdchar (内核空间)

Usually referred to as /dev/mtdX. For MTD character devices, please refer to the MTD overview documentation [2].

  • mtdblock (内核空间)

Usually referred to as /dev/mtdblockX. Do not use mtdblock unless you know exactly what you are doing. For MTD block devices, please refer to the MTD block documentation [3].

  • JFFS2 (内核空间)

Journally Flash File System. Please refer to the MTD JFFS2 documentation [4].

  • UBI (内核空间)

Unsorted Block Images. Please refer to the MTD UBI documentation [5].

  • UBIFS (内核空间)

UBI File System. Please refer to the MTD UBIFS documentation [6].

  • MTD core (内核空间)

The MTD core provides an abstraction layer for raw Flash memories.

  • Raw NAND subsystem (内核空间)

The Raw NAND protocol is used in the MTD subsystem for interfacing NAND Flash memories.

  • SPI-MEM subsystem (内核空间)

The SPI-MEM protocol is used in the MTD subsystem for interfacing all kinds of SPI memories (NORs, NANDs)

  • SPI-NAND subsystem (内核空间)

The SPI-NAND protocol is used in the MTD subsystem for interfacing SPI NAND Flash memories.

  • SPI-NOR subsystem (内核空间)

The SPI-NOR protocol is used in the MTD subsystem for interfacing SPI NOR Flash memories.

  • FMC driver (内核空间) / FMC (硬件)

Please refer to the FMC internal peripheral.

  • QUADSPI driver (Kernel space) / QUADSPI (Hardware)

Please refer to the QUADSPI internal peripheral.

API description

For the Linux MTD API description, please refer to the MTD API documentation [7].

Configuration

Kernel configuration

MTD is activated by default in ST deliveries. Nevertheless, if a specific configuration is needed, this section indicates how MTD can be activated/deactivated in the kernel.

Activate MTD in the kernel configuration with the Linux Menuconfig tool: Menuconfig or how to configure kernel.

SLC NAND Flash memory

[*] Device Drivers --->
    <*> Memory Technology Device (MTD) support --->
        <*> RAW/Parallel NAND Device Support --->
            <*> Support for NAND controller on STM32MP Socs.

SPI NOR/NAND Flash memory 

[*] Device Drivers --->
    <*> Memory Technology Device (MTD) support --->
        Self-contained MTD device drivers --->
            <*> Support most SPI Flash chips (AT26DF, M25P, W25X, ...)      
        <*> SPI NAND device Support
        <*> SPI-NOR device support
    <*> SPI support --->
        -*- SPI memory extension
        <*> STMicroelectronics STM32 QUAD SPI controller

Device tree configuration

The DT configuration can be done thanks to STM32CubeMX.

NAND Flash memory

Please refer to the FMC device tree configuration.

SPI NOR/NAND Flash memory

Please refer to the QUADSPI device tree configuration.

How to use the framework

A file system, which handles read/write/erase operations, can be used over the MTD Framework. Please refer to the UBIFS support through MTD.

You can also interact with the MTD subsystem using the MTD utilities. The MTD utilities[8] are a set of tools that can be used to perform operations on Flash memories through the MTD character interface.

The most common utilities used are:

  • mtdinfo
  • flash_erase
  • flashcp
  • nandwrite
  • nanddump
 root:~# mtdinfo -a
 Count of MTD devices:           9
 Present MTD devices:            mtd0, mtd1, mtd2, mtd3, mtd4, mtd5, mtd6, mtd7, mtd8
 Sysfs interface supported:      yes

 mtd0
 Name:                           fsbl
 Type:                           nand
 Eraseblock size:                262144 bytes, 256.0 KiB
 Amount of eraseblocks:          8 (2097152 bytes, 2.0 MiB)
 Minimum input/output unit size: 4096 bytes
 Sub-page size:                  4096 bytes
 OOB size:                       224 bytes
 Character device major/minor:   90:0
 Bad blocks are allowed:         true
 Device is writable:             true

 mtd1
 Name:                           ssbl
 Type:                           nand
 Eraseblock size:                262144 bytes, 256.0 KiB
 Amount of eraseblocks:          8 (2097152 bytes, 2.0 MiB)
 Minimum input/output unit size: 4096 bytes
 Sub-page size:                  4096 bytes
 OOB size:                       224 bytes
 Character device major/minor:   90:2
 Bad blocks are allowed:         true
 Device is writable:             true

 mtd2
 Name:                           UBI
 Type:                           nand
 Eraseblock size:                262144 bytes, 256.0 KiB
 Amount of eraseblocks:          4078 (1069023232 bytes, 1019.5 MiB)
 Minimum input/output unit size: 4096 bytes
 Sub-page size:                  4096 bytes
 OOB size:                       224 bytes
 Character device major/minor:   90:4
 Bad blocks are allowed:         true
 Device is writable:             true

 mtd3
 Name:                           fsbl1
 Type:                           nor
 Eraseblock size:                65536 bytes, 64.0 KiB
 Amount of eraseblocks:          4 (262144 bytes, 256.0 KiB)
 Minimum input/output unit size: 1 byte
 Sub-page size:                  1 byte
 Character device major/minor:   90:6
 Bad blocks are allowed:         false
 Device is writable:             true

 mtd4
 Name:                           fsbl2
 Type:                           nor
 Eraseblock size:                65536 bytes, 64.0 KiB
 Amount of eraseblocks:          4 (262144 bytes, 256.0 KiB)
 Minimum input/output unit size: 1 byte
 Sub-page size:                  1 byte
 Character device major/minor:   90:8
 Bad blocks are allowed:         false
 Device is writable:             true

 mtd5
 Name:                           ssbl
 Type:                           nor
 Eraseblock size:                65536 bytes, 64.0 KiB
 Amount of eraseblocks:          32 (2097152 bytes, 2.0 MiB)
 Minimum input/output unit size: 1 byte
 Sub-page size:                  1 byte
 Character device major/minor:   90:10
 Bad blocks are allowed:         false
 Device is writable:             true

 mtd6
 Name:                           logo
 Type:                           nor
 Eraseblock size:                65536 bytes, 64.0 KiB
 Amount of eraseblocks:          4 (262144 bytes, 256.0 KiB)
 Minimum input/output unit size: 1 byte
 Sub-page size:                  1 byte
 Character device major/minor:   90:12
 Bad blocks are allowed:         false
 Device is writable:             true

 mtd7
 Name:                           nor_user
 Type:                           nor
 Eraseblock size:                65536 bytes, 64.0 KiB
 Amount of eraseblocks:          980 (64225280 bytes, 61.2 MiB)
 Minimum input/output unit size: 1 byte
 Sub-page size:                  1 byte
 Character device major/minor:   90:14
 Bad blocks are allowed:         false
 Device is writable:             true

 mtd8
 Name:                           58003000.qspi
 Type:                           nor
 Eraseblock size:                65536 bytes, 64.0 KiB
 Amount of eraseblocks:          1024 (67108864 bytes, 64.0 MiB)
 Minimum input/output unit size: 1 byte
 Sub-page size:                  1 byte
 Character device major/minor:   90:16
 Bad blocks are allowed:         false
 Device is writable:             true

How to trace and debug the framework

How to monitor

The sysfs interface provides detail information on each mtd device. 

 root:~# cat /sys/class/mtd/mtd0/name
 fsbl
 root:~# cat /sys/class/mtd/mtd0/type
 nand
 root:~# cat /sys/class/mtd/mtd0/erasesize
 262144
 root:~# cat /sys/class/mtd/mtd0/ecc_strength
 8
 root:~# cat /sys/class/mtd/mtd0/bad_blocks
 0
 root:~# cat /sys/class/mtd/mtd0/ecc_failures
 0

How to trace

A detail dynamic trace is available here How to use the kernel dynamic debug. 

 root:~# echo "file drivers/mtd/* +p" > /sys/kernel/debug/dynamic_debug/control

Source code location

The MTD framework is drivers/mtd | |}} here .

To go further

Please refer to the MTD FAQs documentation [9].

References

Please refer to the following links for full description:

  1. ↑ Documentation/filesystems/vfs.txt | |}} VFS
  2. ↑ MTD overview
  3. ↑ MTD block
  4. ↑ MTD JFFS2
  5. ↑ MTD UBI
  6. ↑ MTD UBIFS
  7. ↑ MTD API
  8. ↑ MTD utils
  9. ↑ MTD FAQs


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