Hi Sebastian, On 08/04/2015 07:58 AM, Sebastian Andrzej Siewior wrote: > On 08/03/2015 09:32 PM, Peter Hurley wrote: > >>> You mean a function in 8250-dma API which does what I did just here >>> with the wait_event() and the wake_up in the callback? That way I could >>> move the termios_wait into the dma struct instead of keeping in the >>> omap specific part. I am also not sure if OMAP is the only one that may >>> hang here or the other people just didn't notice it yet. >> >> Exactly; and we need to fix DMA wrt x_char anyway. >> >> Going back to the dmaengine api, I think something like this might work >> (as a first approximation): >> >> dma_sync_wait(dma->txchan, dma->tx_cookie); >> dmaengine_pause(dma->txchan); >> >> /* remainder of set_termios */ >> >> dmaengine_resume(dma->txchan); >> >> We could require 8250 core dma to support pause/resume. > > I would prefer the waitqueue approach. > You can't do this while holding the port lock. The lock is taken with > irqs off so may not see the transfer completing. > Why do you pause the channel? It may not work without an active > descriptor and a start without "resume" should work. Also you must > ensure that DMA's complete callback does not start another transfer if > there is something queued up (that is why I had the tx_running dance). > I am not sure if a transfer that is active and then paused will not > trigger the hang bug if we change the termios in between. I'll look at/test this this weekend, ok? Regards, Peter Hurley -- 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
