Date: Sun, 18 Jun 2006 17:01:29 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: mainland@apeiron.net Cc: freebsd-usb@freebsd.org Subject: Re: ucom/uftdi dropping bytes, with debug logs FIXED Message-ID: <20060618.170129.1791048549.imp@bsdimp.com> In-Reply-To: <4495D48C.2000601@apeiron.net> References: <e6vefe$5bq$1@sea.gmane.org> <20060617.131208.1589021232.imp@bsdimp.com> <4495D48C.2000601@apeiron.net>
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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
: 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) {
:
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