Date: Mon, 11 Apr 2005 11:21:14 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: bms@spc.org Cc: scottl@samsco.org Subject: Re: A question about hot-pluggable PCI. Message-ID: <20050411.112114.36185200.imp@bsdimp.com> In-Reply-To: <20050411134817.GA4176@empiric.icir.org> References: <20050411082600.GA735@empiric.icir.org> <425A7AB3.7040908@samsco.org> <20050411134817.GA4176@empiric.icir.org>
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In message: <20050411134817.GA4176@empiric.icir.org>
Bruce M Simpson <bms@spc.org> writes:
: On Mon, Apr 11, 2005 at 07:25:07AM -0600, Scott Long wrote:
: > Asking for 'hotplug support' is pretty generic and non-descriptive. Are
: > you asking for device level hotplug support, where we carefully drain
: > transactions out of a device, device driver, and whatever I/O or network
: > or whatever layers are above it? Or are you talking about PCI hotplug
: > support? If so, which de-facto standard? Compaq? IBM? ACPI?
: > PCI-SIG? Something else?
:
: Sorry, I thought my original post was quite clear; in order to support
: my hot-pluggable PCI chassis, FreeBSD needs to grow the ability to manage
: PCI resources without any firmware support (other than possibly the ability
: to route interrupts). Since I sent that mail I looked at the requirements
: list for 5-STABLE and realized this is in fact on it.
The trouble is that 'Hot Plug' pci is a semi-standardized thing.
That's why people are confused. :-) You want to plug in a new PCI
bus, while most people consider hot-plug PCI a way to replace cards in
a running system.
: I looked in src/sys/dev/cardbus/cardbus_cis.c, and Linux's ACPI-based PCI
: hotplug driver, and realised that at the lowest level, they are all in fact
: pretty much doing the same thing -- that is, setting all bits in a BAR, and
: then figuring out the desired aperture size for each BAR, allocating the
: appropriate resources using rman, figuring out base addresses, etc.
Yup.
: We currently rely on the BIOS to do this. The bit I've been discussing with
: Warner is how to deal with the problem of setting subordinate bus numbers,
: though because I can get away without doing that for the 'pcib is an immediate
: child of cardbus' case, I haven't done it.
No we don't. We use what the BIOS provides, but will lazily allocate
the BARs as necessary. We don't open the resource windows on the
bridges, however.
: I had also thought of passing down a 'cold' flag, for pcibX to indicate to
: pciY that this is a 'cold attach' (the BIOS hasn't been anywhere near the
: devices behind this bridge -- it is as fresh as after a RST# assert).
I don't think that's a wise idea.
Warner
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