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02db473e97
Add EEPIOC_SETSPEED ioctl acting like the MTDIOC_SETSPEED ioctl. The default frequency is settable in the Kconfig. Add xx25xx SPI delay control configurations. Signed-off-by: Antoine Juckler <6445757+ajuckler@users.noreply.github.com>
178 lines
7.6 KiB
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178 lines
7.6 KiB
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======
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EEPROM
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======
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.. warning::
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This page describes EEPROM interfacing using a character driver. For the
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more standard MTD interface, refer to the
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:doc:`MTD documentation <../special/mtd>`.
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See `MTD vs character driver <mtd_vs_char_>`_ for when to use each interface.
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EEPROMs are a form of Memory Technology Device (MTD).
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EEPROMs are non-volatile memory like FLASH, but differ in underlying memory
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technology and differ in usage in many respects: They may not be organized into
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blocks (at least from the standpoint of the user) and it is not necessary to
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erase the EEPROM memory before re-writing it.
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In addition, EEPROMs tend to be much smaller than FLASH parts, usually only a
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few kilobytes vs megabytes for FLASH. EEPROM tends to be used to retain a small
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amount of device configuration information; FLASH tends to be used for program
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or massive data storage. For these reasons, it may not be convenient to use the
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more complex MTD interface but instead use the simple character interface
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provided by the EEPROM drivers.
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.. _mtd_vs_char:
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MTD driver vs character driver
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==============================
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MTD driver
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Used when the EEPROM should appear as a block device (`/dev/mtdX`) and is
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intended to be mounted with a filesystem. The MTD layer handles erase, read
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and write granularity.
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Character driver
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Used when direct, random-access reads and writes to the raw EEPROM are
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desired, without the overhead of a filesystem. This is suitable for storing a
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handful of configuration parameters, calibration data, or any small blob that
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does not justify a full filesystem.
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EEPROM Device Support
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=====================
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drivers/eeprom/spi_xx25xx.c
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---------------------------
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This is a driver for SPI EEPROMs that use the same commands as the
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25AA160::
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Manufacturer Device Bytes PgSize SecSize AddrLen
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Microchip
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25xx010A 128 16 16 1
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25xx020A 256 16 16 1
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25AA02UID 256 16 16 1
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25AA02E48 256 16 16 1
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25AA02E64 256 16 16 1
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25xx040 512 16 16 1+bit
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25xx040A 512 16 16 1+bit
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25xx080 1024 16 16 1
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25xx080A 1024 16 16 2
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25xx080B 1024 32 32 2
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25xx080C 1024 16 16 x
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25xx080D 1024 32 32 x
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25xx160 2048 16 16 2
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25xx160A/C 2048 16 16 2
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25xx160B/D 2048 32 32 2
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25xx160C 2048 16 16 2
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25xx160D 2048 32 32 2
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25xx320 4096 32 32 2
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25xx320A 4096 32 32 2
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25xx640 8192 32 32 2
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25xx640A 8192 32 32 2
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25xx128 16384 64 64 2
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25xx256 32768 64 64 2
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25xx512 65536 128 16384 2
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25xx1024 131072 256 32768 3
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Atmel
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AT25010B 128 8 8 1
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AT25020B 256 8 8 1
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AT25040B 512 8 8 1+bit
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AT25080B 1024 32 32 2
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AT25160B 2048 32 32 2
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AT25320B 4096 32 32 2
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AT25640B 8192 32 32 2
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AT25128B 16384 64 64 2
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AT25256B 32768 64 64 2
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AT25512 65536 128 128 2
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AT25M01 131072 256 256 3
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ST Microelectronics
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M95010 128 16 16 1
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M95020 256 16 16 1
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M95040 512 16 16 1+bit
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M95080 1024 32 32 2
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M95160 2048 32 32 2
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M95320 4096 32 32 2
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M95640 8192 32 32 2
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M95128 16384 64 64 2
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M95256 32768 64 64 2
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M95512 65536 128 128 2
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M95M01 131072 256 256 3
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M95M02 262144 256 256 3
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drivers/eeprom/i2c_xx24xx.c
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---------------------------
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This is a driver for I2C EEPROMs that use the same commands as the xx24xx::
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Manufacturer Device Bytes PgSize AddrLen DevAddr
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Microchip
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24xx00 16 1 1 1010000 Special case
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24xx01 128 8 1 1010000
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24xx02 256 8 1 1010000
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24xx04 512 16 1 101000P
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24xx08 1024 16 1 10100PP
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24xx16 2048 16 1 1010PPP
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24xx32 4096 32 2 1010AAA
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24xx64 8192 32 2 1010AAA
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24xx128 16384 64 2 1010AAA
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24xx256 32768 64 2 1010AAA
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24xx512 65536 128 2 1010AAA
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24xx1025 131072 128 2 1010PAA Special case: address
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bit is shifted.
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24xx1026 131072 128 2 1010AAP
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Atmel
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AT24C01 128 8 1 1010AAA
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AT24C02 256 8 1 1010AAA
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AT24C04 512 16 1 1010AAP P bits = word address
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AT24C08 1024 16 1 1010APP
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AT24C16 2048 16 1 1010PPP
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AT24C32 4096 32 2 1010AAA
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AT24C64 8192 32 2 1010AAA
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AT24C128 16384 64 2 10100AA
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AT24C256 32768 64 2 10100AA
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AT24C512 65536 128 2 10100AA
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AT24C1024 131072 256 2 10100AP
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ST Microelectronics
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M24C01 128 16 1 1010AAA
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M24C02 256 16 1 1010AAA
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M24C04 512 16 1 1010AAP
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M24C08 1024 16 1 1010APP
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M24C16 2048 16 1 1010PPP
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M24C32 4096 32 2 1010AAA ID pages supported
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as a separate device
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M24C64 8192 32 2 1010AAA
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M24128 16384 64 2 1010AAA
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M24256 32768 64 2 1010AAA
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M24512 65536 128 2 1010AAA
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M24M01 131072 256 2 1010AAP
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M24M02 262144 256 2 1010APP
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IOCTL Commands
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==============
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The full list of ``ioctl()`` commands can be found in
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``include/nuttx/eeprom/eeprom.h``.
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- ``EEPIOC_GEOMETRY``
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*Argument:* ``struct eeprom_geometry_s *``
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Get the EEPROM geometry
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- ``EEPIOC_SETSPEED``
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*Argument:* ``uint32_t``
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Set the SPI/I2C bus frequency
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File Systems
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============
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Most EEPROM parts are too small to be candidates for use with a file
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system. The character driver interface is optimal for these small parts
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because you can open and access the EEPROM part as if it were a single,
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fixed size file.
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To use them with a file system, it is preferable to use the
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:doc:`MTD driver <../special/mtd>`.
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