From owner-freebsd-current@FreeBSD.ORG Mon Aug 27 20:18:09 2007 Return-Path: Delivered-To: freebsd-current@FreeBSD.ORG Received: by hub.freebsd.org (Postfix, from userid 618) id 0367616A418; Mon, 27 Aug 2007 20:18:09 +0000 (UTC) To: freebsd-current@FreeBSD.ORG, freebsd-net@FreeBSD.ORG Date: Mon, 27 Aug 2007 20:18:08 +0000 (GMT) X-Mailer: ELM [version 2.4ME+ PL54 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <20070827201809.0367616A418@hub.freebsd.org> From: wpaul@FreeBSD.ORG (Bill Paul) Cc: Subject: Bug in vr(4) driver X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Aug 2007 20:18:09 -0000 I recently started writing a driver for the Via Rhine family of chips for VxWorks (they turn up on various x86-based single board systems, and I figured it'd be nice to actually support them out of the box), and along the way, I noticed a subtle bug in the FreeBSD vr(4) driver. The vr_attach() routine unconditionally does this for all supported chips: /* * Windows may put the chip in suspend mode when it * shuts down. Be sure to kick it in the head to wake it * up again. */ VR_CLRBIT(sc, VR_STICKHW, (VR_STICKHW_DS0|VR_STICKHW_DS1)); The problem is, the VR_STICKHW register is not valid on all Rhine devices. The VT86C100A chip, which is present on the D-Link DFE-530TX boards, doesn't support power management, and its register space is only 128 bytes wide. The VR_STICKHW register offset falls outside this range. This may go unnoticed in most scenarios, but if you happen to have another PCI device in your system which is assigned the register space immediately after that of the Rhine, the vr(4) driver will incorrectly stomp it. In my case, the BIOS on my test board decided to put the register space for my PRO/100 ethernet board right next to the Rhine, and the Rhine driver ended up clobbering the IMR register of the PRO/100 device. (Long story short: the board kept locking up on boot. Took me the better part of the morning suss out why.) The strictly correct thing to do would be to check the PCI config space to make sure the device supports the power management capability and only write to the VR_STICKHW register if it does. A less strictly correct but equally effective thing to do would be: /* * Windows may put the chips that support power management into * suspend mode when it shuts down. Be sure to kick it in the * head to wake it up again. */ if (pci_get_device(dev) != VIA_DEVICEID_RHINE) VR_CLRBIT(sc, VR_STICKHW, (VR_STICKHW_DS0|VR_STICKHW_DS1)); This is basically the fix I put into my VxWorks driver. I suggest someone update the FreeBSD driver as well. -Bill -- ============================================================================= -Bill Paul (510) 749-2329 | Senior Engineer, Master of Unix-Fu wpaul@windriver.com | Wind River Systems ============================================================================= "If stupidity got us into this, why can't it get us out?" - Mandy =============================================================================