On 05.01.2022 16:00:34, Sergey Organov wrote: > Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> writes: > > > On Tue, Jan 04, 2022 at 11:32:03AM +0100, Tomasz Moń wrote: > >> Triggering RX interrupt for every byte defeats the purpose of aging > >> timer and leads to interrupt starvation at high baud rates. > >> > >> Increase receiver trigger level to 8 to increase the minimum period > >> between RX interrupts to 8 characters time. The tradeoff is increased > >> latency. In the worst case scenario, where RX data has intercharacter > >> delay slightly less than aging timer (8 characters time), it can take > >> up to 63 characters time for the interrupt to be raised since the > >> reception of the first character. > > > > Why can't you do this dynamically based on the baud rate so as to always > > work properly for all speeds without increased delays for slower ones? > > I don't like the idea of dynamic threshold as I don't think increased > complexity is worth it. > > In fact the threshold works "properly" on any baud rate, as maximum > latency is proportional to the current baud rate, and if somebody does > care about *absolute* latency, increasing baud rate is the primary > solution. Nope - this only works if you have both sides under control.... Which is not the case in our $CUSTROMER's use case. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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