Hi Peter, On Fri, 2015-11-20 at 11:30AM -0500, Peter Hurley wrote: > Hi Sören, > > On 11/20/2015 10:28 AM, Sören Brinkmann wrote: > > On Fri, 2015-11-20 at 07:13AM -0500, Peter Hurley wrote: > >> On 11/19/2015 03:02 PM, Soren Brinkmann wrote: > >>> start_tx must start transmitting characters. Regardless of the state of > >>> the circular buffer, always enable the transmitter hardware. > >> > >> Why? > >> > >> Does cdns_uart_stop_tx() actually stop the transmitter so that > >> data remains in the transmitter? > > > > Well, I saw my system freezing and the cause seemed to be that the UART > > receiver and/or transmitters were disabled while the system was trying > > to print. Hence, I started questioning all locations touching the > > transmitter/receiver enable. I read the docs in > > https://www.kernel.org/doc/Documentation/serial/driver, which simply > > says "Start transmitting characters." for start_tx(). Hence, I thought, > > this function is probably supposed to just do that and start the > > transmitter. I'll test whether this patch can be dropped. > > I don't think that patch would fix any freeze problems, but restarting > the transmitter even if the circ buffer is empty may be necessary to > push out remaining data when the port is restarted after being stopped. > > IOW, something like > > if (uart_tx_stopped(port)) > return; > > .... > > > if (uart_circ_empty(&port->state->xmit) > return; Thanks! I'll change the patch accordingly. > > > Below is a (work-in-progress) serial driver validation test for flow > control handling (it may need some tuning for slow line speeds). > Usual caveats apply. Takes ~40secs @ 115200. I'll try to get that running on my system. Thanks, Sören -- 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
