On 08/06/2015 02:27 PM, Peter Hurley wrote: > Hi Sebastian, Hi Peter, > 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? Sure. I'm currently re-spinning the patches so have everything in proper pieces. While at it I will take a look at x_char. > Regards, > Peter Hurley > Sebastian -- 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
