99 lines
4.3 KiB
Plaintext
99 lines
4.3 KiB
Plaintext
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fmc-write-eeprom
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================
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This module is designed to load a binary file from /lib/firmware and to
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write it to the internal EEPROM of the mezzanine card. This driver uses
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the `busid' generic parameter.
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Overwriting the EEPROM is not something you should do daily, and it is
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expected to only happen during manufacturing. For this reason, the
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module makes it unlikely for the random user to change a working EEPROM.
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However, since the EEPROM may include application-specific information
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other than the identification, later versions of this packages added
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write-support through sysfs. See *note Accessing the EEPROM::.
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To avoid damaging the EEPROM content, the module takes the following
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measures:
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* It accepts a `file=' argument (within /lib/firmware) and if no
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such argument is received, it doesn't write anything to EEPROM
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(i.e. there is no default file name).
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* If the file name ends with `.bin' it is written verbatim starting
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at offset 0.
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* If the file name ends with `.tlv' it is interpreted as
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type-length-value (i.e., it allows writev(2)-like operation).
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* If the file name doesn't match any of the patterns above, it is
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ignored and no write is performed.
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* Only cards listed with `busid=' are written to. If no busid is
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specified, no programming is done (and the probe function of the
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driver will fail).
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Each TLV tuple is formatted in this way: the header is 5 bytes,
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followed by data. The first byte is `w' for write, the next two bytes
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represent the address, in little-endian byte order, and the next two
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represent the data length, in little-endian order. The length does not
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include the header (it is the actual number of bytes to be written).
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This is a real example: that writes 5 bytes at position 0x110:
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spusa.root# od -t x1 -Ax /lib/firmware/try.tlv
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000000 77 10 01 05 00 30 31 32 33 34
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00000a
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spusa.root# insmod /tmp/fmc-write-eeprom.ko busid=0x0200 file=try.tlv
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[19983.391498] spec 0000:03:00.0: write 5 bytes at 0x0110
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[19983.414615] spec 0000:03:00.0: write_eeprom: success
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Please note that you'll most likely want to use SDBFS to build your
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EEPROM image, at least if your mezzanines are being used in the White
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Rabbit environment. For this reason the TLV format is not expected to
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be used much and is not expected to be developed further.
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If you want to try reflashing fake EEPROM devices, you can use the
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fmc-fakedev.ko module (see *note fmc-fakedev::). Whenever you change
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the image starting at offset 0, it will deregister and register again
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after two seconds. Please note, however, that if fmc-write-eeprom is
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still loaded, the system will associate it to the new device, which
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will be reprogrammed and thus will be unloaded after two seconds. The
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following example removes the module after it reflashed fakedev the
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first time.
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spusa.root# insmod fmc-fakedev.ko
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[ 72.984733] fake-fmc: Manufacturer: fake-vendor
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[ 72.989434] fake-fmc: Product name: fake-design-for-testing
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spusa.root# insmod fmc-write-eeprom.ko busid=0 file=fdelay-eeprom.bin; \
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rmmod fmc-write-eeprom
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[ 130.874098] fake-fmc: Matching a generic driver (no ID)
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[ 130.887845] fake-fmc: programming 6155 bytes
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[ 130.894567] fake-fmc: write_eeprom: success
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[ 132.895794] fake-fmc: Manufacturer: CERN
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[ 132.899872] fake-fmc: Product name: FmcDelay1ns4cha
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Accessing the EEPROM
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=====================
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The bus creates a sysfs binary file called eeprom for each mezzanine it
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knows about:
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spusa.root# cd /sys/bus/fmc/devices; ls -l */eeprom
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-r--r--r-- 1 root root 8192 Feb 21 12:30 FmcAdc100m14b4cha-0800/eeprom
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-r--r--r-- 1 root root 8192 Feb 21 12:30 FmcDelay1ns4cha-0200/eeprom
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-r--r--r-- 1 root root 8192 Feb 21 12:30 FmcDio5cha-0400/eeprom
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Everybody can read the files and the superuser can also modify it, but
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the operation may on the carrier driver, if the carrier is unable to
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access the I2C bus. For example, the spec driver can access the bus
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only with its golden gateware: after a mezzanine driver reprogrammed
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the FPGA with a custom circuit, the carrier is unable to access the
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EEPROM and returns ENOTSUPP.
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An alternative way to write the EEPROM is the mezzanine driver
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fmc-write-eeprom (See *note fmc-write-eeprom::), but the procedure is
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more complex.
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