Date: Wed, 30 Sep 2009 20:49:22 +0930 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: freebsd-stable@freebsd.org Subject: PCI write oddity Message-ID: <200909302049.43344.doconnor@gsoft.com.au>
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--nextPart2229981.rP8oQUmKAR Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Hi, I have a custom device driver for a PCI RS485 card - it has a 16550 and=20 a PLX PCI bridge on it and I recently found something quite odd. We used to run the link at 9600 but with some more recent modules we've=20 decided to up it to 115200, so I changed the baud rate easily enough..=20 However while the bit rate is correct each byte going out has a 1=20 millisecond delay(!). What is really odd is that when I added some=20 debugging to log how long each write to the FIFO register took I=20 discovered it was 1 millisecond. Reads from the same register take ~5 usec which seems more like it. Does anyone have any idea why it would be so damn slow? =2D-=20 Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C --nextPart2229981.rP8oQUmKAR Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.12 (FreeBSD) iD8DBQBKwz7P5ZPcIHs/zowRAsC7AJsFOOxJ6EROLCyckvq9KpgK/KATnACgpiEM La7/qKxiHNZJWZz0CG6Vby0= =Qvtl -----END PGP SIGNATURE----- --nextPart2229981.rP8oQUmKAR--
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