Date: Mon, 19 Jun 2006 09:32:05 +0200 From: Hans Petter Selasky <hselasky@c2i.net> To: freebsd-usb@freebsd.org Cc: mainland@apeiron.net Subject: Re: ucom/uftdi dropping bytes, with debug logs FIXED Message-ID: <200606190932.07437.hselasky@c2i.net> In-Reply-To: <20060618.170129.1791048549.imp@bsdimp.com> References: <e6vefe$5bq$1@sea.gmane.org> <4495D48C.2000601@apeiron.net> <20060618.170129.1791048549.imp@bsdimp.com>
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On Monday 19 June 2006 01:01, M. Warner Losh wrote: > In message: <4495D48C.2000601@apeiron.net> > > Geoffrey Mainland <mainland@apeiron.net> writes: > : M. Warner Losh wrote: > : > In message: <e6vefe$5bq$1@sea.gmane.org> > : > > : > Geoffrey Mainland <mainland@apeiron.net> writes: > : > : The fact that this runs fine under VMWare makes me strongly suspect a > : > : timing issue that is fixed by some sort of buffering at the VMWare > : > : level. Where should I start to look to hack something in to test > : > : this? The ucom driver seems to be setting up the read transfers that > : > : don't complete on time. > : > > : > I'd start looking into ucom.c and uftdi.c. > : > > : > Warner > : > : Here's a diff against ucom.c version 1.57 that fixes the problem for me. > : I'm sure this is not the "correct" fix, but it stops bytes from being > : dropped :). I assume aborting the read and immediately restarting it > : flushes some pending data. Why is ucomstop is called so frequently by > : the tty code? > > I don't know. Sure is weird. I've seen tip take 100% of the CPU when > talking with a uftdi dongle too. > > Warner It does not make sense to re-start the read pipe when one is flushing the output pipe. Probably the cause of a lot of quirks ... > > : Geoff > : > : Index: ucom.c > : =================================================================== > : --- ucom.c (revision 3) > : +++ ucom.c (working copy) > : @@ -622,10 +622,12 @@ > : > : DPRINTF(("ucomstop: %d\n", flag)); > : > : +#if 0 > : if ((flag & FREAD) && (sc->sc_state & UCS_RXSTOP) == 0) { > : DPRINTF(("ucomstop: read\n")); > : ucomstopread(sc); > : ucomstartread(sc); > : +#endif > : } > : > : if (flag & FWRITE) { > : --HPS
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