Date: Sat, 15 Nov 1997 13:53:51 +1100 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, mouth@ibm.net Cc: hackers@FreeBSD.ORG Subject: Re: Status of 650 UART support Message-ID: <199711150253.NAA25462@godzilla.zeta.org.au>
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>>interrupts need to be reenabled on the polled ports as soon as = >everything >> in them is polled > >Only if your clock interrupt is too slow. But I wanted to change that It is too slow (10 msec). >Would it be feasible to tick the clock every 1ms to schedule UART >polling and on every fifth tick run the usual kernel scheduling? There would be no point interrupting 10 times as often just to poll twice as often. Polling every 1ms tick would be often enough for there to be almost no need for serial input interrupts or auto RTS flow control at 115200 bps (since 14 character times is 1.216ms which is slightly more than the polling interval). OTOH, the polling routines can't be guaranteed to run (at low priority) every 1ms - even the current 10ms can't be guaranteed - so auto RTS flow control would still be necessary. I think this would be a pessimization in practice. First you waste cycles processing more clock interrupts, then you waste more by polling more often. Bruce
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