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Re: Questions about pci configuration and the mpt(4) driver
On Sat, Nov 17, 2012 at 02:18:18AM -0800, Brian Buhrow wrote:
> Hello. I've been working on an issue with the mpt(4) driver, the
> driver for the LSI Fusion SCSI controller cards and raid cards. In the
> process of working through the issue, I've discovered that the mpt(4)
> driver is very fragile if the need to reset the hardware arises. In
> particular, if a hardware reset is done, all of the pci configuration
> registers get zorched, causing interrupt handling to fail and requests to
> get stuck in the driver and hardware's queue.
When does the need for a reset arise? Is the cause a driver bug or a
It sounds to me like you should detach the device (perhaps resetting
in the final stages of the detachment---i.e., before unmapping the
registers) and re-attach it.
Since detachment ordinarily loses all of the software state, you may
need to stash the outstanding requests somewhere that the re-attached
device can find them.
> I've been looking for
> examples of how to reset the PCI registers after such a reset, but neither
> the OpenBSD or FreeBSD drivers offer a clue. All BSD drivers I've looked
> at lament the problem, but none provide a solution. I've considered
> extracting the PCI initialization process from the mpt_pci_attach() routine
> into a separate function that can be called at any time while things are
> running, but there must be a reason this hasn't been done already and why I
> don't see any examples that look obvious to me of any drivers that do this.
> Is it safe to call pci_intr_disestablish() and pci_intr_establish() during
> the course of normal multi-user operation for a particular driver as a
> means of re-attaching interrupts to a device that's forgotten how to
> generate them? Are there any examples of drivers that do a complete reset
> of the hardware, including pci and pci interrupt settings while continuing
> to operate in multi-user mode?
dyoung%pobox.com@localhost Urbana, IL (217) 721-9981
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