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FDT data. The sector size must be a multiple of the device's page size. If not configured, use the historical default of the device page size. Setting the disk sector size to 512 or 4096 allows a variety of standard filesystems to be used on the device. Of course you wouldn't want to be writing frequently to a SPI flash chip like it was a disk drive, but for data that gets written once (or rarely) and read often, using a standard filesystem is a nice convenient thing.
185 lines
5.2 KiB
Groff
185 lines
5.2 KiB
Groff
.\"
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.\" Copyright (c) 2019 Ian Lepore <ian@freebsd.org>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 2, 2019
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.Dt AT45D 4
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.Os
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.Sh NAME
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.Nm at45d
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.Nd driver for DataFlash(tm) non-volatile storage devices
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device at45d"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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at45d_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for the family of non-volatile storage
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devices known collectively as DataFlash(tm).
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DataFlash chips typically have part numbers beginning with AT45DB.
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The
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.Nm
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driver supports only the SPI bus versions of each AT45DB device,
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indicated by the last digit of the part number being 1 or 2.
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.Pp
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The
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.Nm
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driver uses opcode 0x9f to read the manufacturer and device ID
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data to determine whether the device is supported.
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The device ID is looked up using a table of data within the driver
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which describes the attributes of each supported device,
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such as block size, sector size, and device capacity.
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When a supported device is found, the
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.Nm
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driver creates a disk device and makes it accessible at
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.Pa /dev/flash/at45d? .
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The new disk device is then tasted by the available
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.Xr geom 4
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modules as with any disk device.
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.Sh HARDWARE
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The
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.Nm
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driver provides support for the following devices:
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.Pp
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.Bl -bullet -compact
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.It
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AT45DB011B
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.It
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AT45DB021B
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.It
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AT45DB041x
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.It
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AT45DB081B
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.It
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AT45DB161x
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.It
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AT45DB321x
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.It
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AT45DB321x
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.It
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AT45DB641E
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.It
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AT45DB642x
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.El
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.Sh FDT CONFIGURATION
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On an
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.Xr fdt 4
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based system, the
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.Nm
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device is defined as a slave device subnode
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of the SPI bus controller node.
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All properties documented in the
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.Va spibus.txt
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bindings document can be used with the
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.Nm
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device.
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The most commonly-used ones are documented below.
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.Pp
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The following properties are required in the
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.Nm
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device subnode:
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.Bl -tag -width indent
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.It Va compatible
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Must be the string "atmel,at45".
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.It Va reg
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Chip select address of device.
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.It Va spi-max-frequency
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The maximum bus frequency to use when communicating with this slave device.
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Actual bus speed may be lower, depending on the capabilities of the SPI
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bus controller hardware.
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.El
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.Pp
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The following properties are optional for the
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.Nm
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device subnode:
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.Bl -tag -width indent
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.It Va freebsd,sectorsize
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The sector size of the disk created for this storage device.
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It must be a multiple of the device's page size.
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The default is the device page size.
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.It Va spi-cpha
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Empty property indicating the slave device requires shifted clock
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phase (CPHA) mode.
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.It Va spi-cpol
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Empty property indicating the slave device requires inverse clock
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polarity (CPOL) mode.
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.It Va spi-cs-high
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Empty property indicating the slave device requires chip select active high.
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.El
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.Sh HINTS CONFIGURATION
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On a
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.Xr device.hints 5
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based system, such as
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.Li MIPS ,
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these values are configurable for
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.Nm :
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.Bl -tag -width indent
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.It Va hint.at45d.%d.at
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The spibus the
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.Nm
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instance is attached to.
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.It Va hint.at45d.%d.clock
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The maximum bus frequency to use when communicating with this device.
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Actual bus speed may be lower, depending on the capabilities of the SPI
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bus controller hardware.
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.It Va hint.at45d.%d.cs
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The chip-select number to assert when performing I/O for this device.
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Set the high bit (1 << 31) to invert the logic level of the chip select line.
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.It Va hint.at45d.%d.mode
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The SPI mode (0-3) to use when communicating with this device.
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.It Va hint.at45d.%d.sectorsize
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The sector size of the disk created for this storage device.
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It must be a multiple of the device's page size.
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The default is the device page size.
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.El
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.Sh FILES
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.Bl -tag -width /dev/flash/at45d?
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.It Pa /dev/flash/at45d?
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Provides read/write access to the storage device.
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.It Pa /dev/flash/spi?
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An alias for the
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.Pa /dev/at45d?
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device, for backwards compatibility with older versions of the driver.
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.El
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.Sh SEE ALSO
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.Xr fdt 4 ,
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.Xr geom 4
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.Sh HISTORY
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The
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.Nm
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driver first appeared in
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.Fx 6.0 .
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