Bug in vr(4) driver

Bill Paul wpaul at FreeBSD.ORG
Mon Aug 27 13:18:09 PDT 2007

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

         * 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.

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)

This is basically the fix I put into my VxWorks driver. I suggest someone
update the FreeBSD driver as well.


-Bill Paul            (510) 749-2329 | Senior Engineer, Master of Unix-Fu
                 wpaul at windriver.com | Wind River Systems
      "If stupidity got us into this, why can't it get us out?" - Mandy

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