Date: Tue, 09 Dec 2008 14:20:31 -0500 From: Mike Tancsa <mike@sentex.net> To: Scott Long <scottl@samsco.org> Cc: Marcel Moolenaar <xcllnt@mac.com>, freebsd-current@freebsd.org Subject: Re: uart vs sio differences ? Message-ID: <200812091920.mB9JKWD1048771@lava.sentex.ca> In-Reply-To: <493EA759.4000504@samsco.org> References: <200812081621.mB8GLMxB041498@lava.sentex.ca> <ED8BC24F-EAC3-4266-AF54-4C6262DDC156@mac.com> <200812081906.mB8J6oha042222@lava.sentex.ca> <CF6E0ACA-CCFA-4A35-A88F-C95484309A78@mac.com> <200812082049.mB8KnHSN042710@lava.sentex.ca> <84A7F176-5A74-48AC-859A-C0D4C7CBCB48@mac.com> <7.1.0.9.0.20081208173515.13f62e88@sentex.net> <200812091457.mB9EvLSD047534@lava.sentex.ca> <493EA759.4000504@samsco.org>
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At 12:14 PM 12/9/2008, Scott Long wrote:
buffer. I'll see if I can come up with some code for this today. Not
>sure if the same can be done for ucom since the USB stack below it
>presents a lot more complications and overhead.
Hi Scott,
It seems to work in the USB case if I reduce the receive and
xmit buffers. Do you know if there are any nasty unintended side
effects of doing this ?
I did the follow simple hack to the driver to get our app to work.
--- sys/dev/usb/uftdi.c.orig 2008-12-09 11:47:02.000000000 -0500
+++ sys/dev/usb/uftdi.c 2008-12-09 11:47:05.000000000 -0500
@@ -198,6 +198,7 @@
usb_interface_descriptor_t *id;
usb_endpoint_descriptor_t *ed;
int i;
+ unsigned int ivar;
usbd_status err;
struct ucom_softc *ucom = &sc->sc_ucom;
DPRINTFN(10,("\nuftdi_attach: sc=%p\n", sc));
@@ -353,11 +354,27 @@
ucom->sc_portno = FTDI_PIT_SIOA;
else
ucom->sc_portno = FTDI_PIT_SIOA + id->bInterfaceNumber;
- /* bulkin, bulkout set above */
- ucom->sc_ibufsize = UFTDIIBUFSIZE;
- ucom->sc_obufsize = UFTDIOBUFSIZE - sc->sc_hdrlen;
- ucom->sc_ibufsizepad = UFTDIIBUFSIZE;
+ /* For certain low speed / timing sensitive applications
having the buffers too large causes
+ data to be stuck in the queue too long. By adding a
tuneable, users can lower the buffer
+ size to what works for their application
+ */
+
+ if (!resource_int_value(
+ "uftdi", device_get_unit(ucom->sc_dev), "buffersize",
&ivar) && (ivar > sc->sc_hdrlen && ivar <= UFTDIIBUFSIZE) ) {
+ ucom->sc_ibufsize = ivar;
+ ucom->sc_obufsize = ivar - sc->sc_hdrlen;
+ ucom->sc_ibufsizepad = ivar;;
+ device_printf(ucom->sc_dev, "Setting buffers
to %d\n",ivar);
+ }
+ else
+ {
+ ucom->sc_ibufsize = UFTDIIBUFSIZE;
+ ucom->sc_obufsize = UFTDIOBUFSIZE - sc->sc_hdrlen;
+ ucom->sc_ibufsizepad = UFTDIIBUFSIZE;
+ device_printf(ucom->sc_dev, "Setting buffers
to default of %d\n",UFTDIIBUFSIZE);
+
+ }
ucom->sc_opkthdrlen = sc->sc_hdrlen;
---Mike
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