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

MTD v1.1.0.png


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)

通常称为/ dev / mtdX。 对于MTD字符设备，请参考MTD概述文档 [2].

  • mtdblock (内核空间)

通常称为/ dev / mtdblockX。 除非您确切知道自己在做什么，否则不要使用mtdblock。 对于MTD块设备，请参考MTD块文档[3].

  • JFFS2 (内核空间)

日记Flash文件系统。 请参考MTD JFFS2文档 [4].

  • UBI (内核空间)

未分类的块图像。 请参考MTD UBI文档 [5].

  • UBIFS (内核空间)

UBI文件系统。 请参考MTD UBIFS文档[6].

  • MTD core (内核空间)

MTD内核为原始闪存提供了一个抽象层。

  • Raw NAND subsystem (内核空间)

MTD子系统中使用Raw NAND协议来连接NAND闪存。

  • SPI-MEM subsystem (内核空间)

SPI-MEM协议在MTD子系统中用于连接各种SPI存储器（NOR，NAND）

  • SPI-NAND subsystem (内核空间)

SPI-NAND协议在MTD子系统中用于连接SPI NAND闪存。

  • SPI-NOR subsystem (内核空间)

MTD子系统中使用SPI-NOR协议来连接SPI NOR闪存。

  • FMC driver (内核空间) / FMC (硬件)

请参阅FMC internal peripheral.

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

请参阅QUADSPI internal peripheral.

API description

有关Linux MTD API的描述，请参阅MTD API文档 [7].

Configuration

Kernel configuration

ST交货中默认激活MTD。 但是，如果需要特定的配置，则本节说明如何在内核中激活/停用MTD。

使用Linux Menuconfig工具在内核配置中激活MTD：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

借助STM32CubeMX可以完成DT配置。

NAND Flash memory

请参考 FMC device tree configuration.

SPI NOR/NAND Flash memory

请参考 QUADSPI device tree configuration.

How to use the framework

可以在MTD框架上使用处理读/写/擦除操作的文件系统。 请参考UBIFS support through MTD.

您还可以使用MTD实用程序与MTD子系统进行交互。 MTD实用程序[8] 是一组工具，可用于通过MTD字符接口对闪存执行操作。 最常用的实用程序是：

  • 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

sysfs界面提供有关每个mtd设备的详细信息。 

 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

详细动态跟踪可在此处 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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