Hi Peter, On 20.11.2015 18:16, Peter Hurley wrote: > On 11/20/2015 11:58 AM, Sören Brinkmann wrote: >> On Fri, 2015-11-20 at 11:30AM -0500, Peter Hurley wrote: >>> 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. > > The test below should pass too, but I know it won't because this xilinx > driver isn't handling x_char at all. > > Aside: does this h/w have rts driver/cts receiver? > > --- >% --- > --- /dev/null 2015-11-20 07:19:13.265468435 -0500 > +++ xchar.c 2015-11-20 11:55:26.210233102 -0500 > @@ -0,0 +1,354 @@ > +/* > + * x_char unit test for tty drivers All these tests looks very interesting. Do you have any any work-in-progress repo with other tests? It will be good to run all of them to validate our drivers. Thanks, Michal -- 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
