Hi, I'm adapting the sc16is7xx.c driver (written for serial_core) for use with SPI, plus some bug fixes along the way. I'm experiencing timed-out hangs. The following description is brief but should be easy to understand. Let me know if I've missed out on details. Since start_tx() must not sleep, sc16is7xx:start_tx() calls schedule_work() on a worker process which calls its internal start_tx(). Usually, the call chain looks like this for writing data: sc16is7xx (0): startup() sc16is7xx (0): set_termios() sc:uw <-- serial_core:uart_write() sc:_us <-- serial_core:__uart_start() sched sc16is7xx (): -> TX sc:ufc <-- serial_core:uart_flush_chars() sc:_us <-- serial_core:__uart_start() sched sc16is7xx (): <- TX sc16is7xx (): -> TX sc16is7xx (): <- TX sc16is7xx (0): tx_empty() sc16is7xx (0): stop_rx sc16is7xx (0): tx_empty() sc16is7xx (0): shutdown() But occasionally, it looks like this: sc16is7xx (0): startup() sc16is7xx (0): set_termios() sc:uw sc:_us sched sc:ufc sc:_us sc16is7xx (0): NOT sched TX <-- since already pending sc16is7xx (): -> TX sc16is7xx (): TX -> 64 sc16is7xx (): <- TX nothing happens for about a minute... sc16is7xx (0): tx_empty() sc16is7xx (0): stop_rx sc16is7xx (0): tx_empty() sc16is7xx (0): shutdown() The reason, as far as I can tell, is that both tty_operations::flush_chars() and tty_operations::uart_write() are mapped to __uart_write() which calls driver:start_tx(), and both expect the operations to be synchronous. But alas, I cannot do that, so add SMP to the mix and uart_flush_chars() never starts, and something in the tty layer times out. What would be the simplest/best solution to this problem, short of rewrtiing the driver to use th etty layer? I have a hack in place (set a flag in start_tx() if work already q'd and check it in handle_tx() to run the code again), but I'd like a better solution. Thanks in advance, Mikael Jansson -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
