soundwire: stream: Poll for DP prepare to avoid interrupt deadlock #5649
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Replace the wait_for_completion_timeout() in sdw_prep_deprep_slave_ports() with a read_poll_timeout(). The original intent of the wait_for_completion_timeout() was to wait for the port prepare interrupt. But at this time the code is holding the bus_lock, which prevents the interrupt handler from running. Because of this, the port_prep completion will not be signaled and the wait_for_completion_timeout() will always timeout. Rewriting the code to avoid taking the bus_lock carries risks, and needs careful consideration of the consequences. It is safer and simpler to replace the completion with a simple register poll. As the code is holding the bus_lock, it is already blocking other activity so consuming control channel bandwidth for polling isn't really a concern. Signed-off-by: Richard Fitzgerald <[email protected]>
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Replace the wait_for_completion_timeout() in sdw_prep_deprep_slave_ports() with a read_poll_timeout().
The original intent of the wait_for_completion_timeout() was to wait for the port prepare interrupt. But at this time the code is holding the bus_lock, which prevents the interrupt handler from running. Because of this, the port_prep completion will not be signaled and the wait_for_completion_timeout() will always timeout.
Rewriting the code to avoid taking the bus_lock carries risks, and needs careful consideration of the consequences. It is safer and simpler to replace the completion with a simple register poll.
As the code is holding the bus_lock, it is already blocking other activity so consuming control channel bandwidth for polling isn't really a concern.