[Backport v2.7-branch] drivers: i2c: i2c_dw: Fixed integer overflow in i2c_dw_data_ask(). #67345
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The controller can implement a reception FIFO as deep as 256 bytes. However, the computation made by the driver code to determine how many bytes can be asked is stored in a signed 8-bit variable called rx_empty. If the reception FIFO depth is greater or equal to 128 bytes and the FIFO is currently empty, the rx_empty value will be 128 (or more), which stands for a negative value as the variable is signed. Thus, the later code checking if the FIFO is full will run while it should not and exit from the i2c_dw_data_ask() function too early. This hangs the controller in an infinite loop of interrupt storm because the interrupt flags are never cleared. Storing the rx_empty empty on a signed 32-bit variable instead of a 8-bit one solves the issue and is compliant with the controller hardware specifications of a maximum FIFO depth of 256 bytes. It has been agreed with upstream maintainers to change the type of the variables tx_empty, rx_empty, cnt, rx_buffer_depth and tx_buffer_depth to plain int because it is most effectively handled by the CPUs. Using 8-bit or 16-bit variables had no meaning here. Signed-off-by: Adrien Ricciardi <[email protected]> (cherry picked from commit 4824e40)
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@dkalowsk - this one needs a bug report. Would you be up for writing one? |
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Issue: #67688 |
dcpleung
approved these changes
Jan 16, 2024
cfriedt
approved these changes
Jan 16, 2024
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Backport 4824e40 from #66685.
Fixes #67692