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With IC_INTR_RX_FULL slave interrupt handler reads data in a loop until RX FIFO is empty. When testing with the slave-eeprom, each transaction has 2 bytes for address/index and 1 byte for value, the address byte can be written as data byte due to dropping STOP condition. In the test below, the master continuously writes to the slave, first 2 bytes are index, 3rd byte is value and follow by a STOP condition. i2c_write: i2c-3 #0 a=04b f=0000 l=3 [00-D1-D1] i2c_write: i2c-3 #0 a=04b f=0000 l=3 [00-D2-D2] i2c_write: i2c-3 #0 a=04b f=0000 l=3 [00-D3-D3] Upon receiving STOP condition slave eeprom would reset `idx_write_cnt` so next 2 bytes can be treated as buffer index for upcoming transaction. Supposedly the slave eeprom buffer would be written as EEPROM[0x00D1] = 0xD1 EEPROM[0x00D2] = 0xD2 EEPROM[0x00D3] = 0xD3 When CPU load is high the slave irq handler may not read fast enough, the interrupt status can be seen as 0x204 with both DW_IC_INTR_STOP_DET (0x200) and DW_IC_INTR_RX_FULL (0x4) bits. The slave device may see the transactions below. 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1794 : INTR_STAT=0x204 0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x1790 : INTR_STAT=0x200 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x1594 : INTR_STAT=0x4 After `D1` is received, read loop continues to read `00` which is the first bype of next index. Since STOP condition is ignored by the loop, eeprom buffer index increased to `D2` and `00` is written as value. So the slave eeprom buffer becomes EEPROM[0x00D1] = 0xD1 EEPROM[0x00D2] = 0x00 EEPROM[0x00D3] = 0xD3 The fix is to use `FIRST_DATA_BYTE` (bit 11) in `IC_DATA_CMD` to split the transactions. The first index byte in this case would have bit 11 set. Check this indication to inject I2C_SLAVE_WRITE_REQUESTED event which will reset `idx_write_cnt` in slave eeprom. Signed-off-by: David Zheng <david.zheng@intel.com> Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com> Signed-off-by: Wolfram Sang <wsa@kernel.org> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.