mirror of https://gitee.com/openkylin/linux.git
67 lines
2.6 KiB
ReStructuredText
67 lines
2.6 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0
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================================
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Linux I2C slave testunit backend
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================================
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by Wolfram Sang <wsa@sang-engineering.com> in 2020
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This backend can be used to trigger test cases for I2C bus masters which
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require a remote device with certain capabilities (and which are usually not so
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easy to obtain). Examples include multi-master testing, and SMBus Host Notify
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testing. For some tests, the I2C slave controller must be able to switch
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between master and slave mode because it needs to send data, too.
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Note that this is a device for testing and debugging. It should not be enabled
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in a production build. And while there is some versioning and we try hard to
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keep backward compatibility, there is no stable ABI guaranteed!
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Instantiating the device is regular. Example for bus 0, address 0x30:
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# echo "slave-testunit 0x1030" > /sys/bus/i2c/devices/i2c-0/new_device
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After that, you will have a write-only device listening. Reads will return an
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8-bit version number. The device consists of 4 8-bit registers and all must be
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written to start a testcase, i.e. you must always write 4 bytes to the device.
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The registers are:
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0x00 CMD - which test to trigger
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0x01 DATAL - configuration byte 1 for the test
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0x02 DATAH - configuration byte 2 for the test
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0x03 DELAY - delay in n * 10ms until test is started
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Using 'i2cset' from the i2c-tools package, the generic command looks like:
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# i2cset -y <bus_num> <testunit_address> <CMD> <DATAL> <DATAH> <DELAY> i
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DELAY is a generic parameter which will delay the execution of the test in CMD.
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The commands are described in the following section. An invalid command will
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result in the transfer not being acknowledged.
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Commands
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--------
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0x00 NOOP (reserved for future use)
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0x01 READ_BYTES (also needs master mode)
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DATAL - address to read data from
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DATAH - number of bytes to read
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This is useful to test if your bus master driver is handling multi-master
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correctly. You can trigger the testunit to read bytes from another device on
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the bus. If the bus master under test also wants to access the bus at the same
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time, the bus will be busy. Example to read 128 bytes from device 0x50 after
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50ms of delay:
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# i2cset -y 0 0x30 0x01 0x50 0x80 0x05 i
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0x02 SMBUS_HOST_NOTIFY (also needs master mode)
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DATAL - low byte of the status word to send
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DATAH - high byte of the status word to send
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This test will send an SMBUS_HOST_NOTIFY message to the host. Note that the
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status word is currently ignored in the Linux Kernel. Example to send a
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notification after 10ms:
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# i2cset -y 0 0x30 0x02 0x42 0x64 0x01 i
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