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SubjectRe: [patch 2.5] tg3.c: pci_{save,restore}_extended_state
On Fri, Jan 24, 2003 at 03:34:02PM -0500, Jeff Garzik wrote:
> On Fri, Jan 24, 2003 at 03:24:53PM -0500, Wiedemeier, Jeff wrote:
> > On Fri, Jan 24, 2003 at 03:05:38PM -0500, Jeff Garzik wrote:
> > If the intent is to just not use MSI on tg3 devices, I can use the pci
> > quirks to make sure that MSI gets turned off for tg3 devices.
>
> hmmm, maybe I am missing something?

Quoting section 6.8.1.3 of the PCI 2.2 spec (talking about message
control in PCI config space):

This register provides system software control over MSI. After reset,
MSI is disabled (bit 0 is cleared) and the function requests servicing
via its INTx# pin (if supported). System sofware can enable MSI by
setting bit 0 of this register. System software is permitted to
modify the Message Control register's read/write bits and fields.
A device driver is not permitted to modify the Message Control
register's read/write bits and fields.

> AFAICS, this is a per-driver decision, and needs to be done at the
> driver level, in the tg3 driver source.

The last sentence in the quote above indicates that it is not intended
(by the PCI spec) to be a per-driver decision, but rather a system
decision. The messages used are also a per-bus system resource and how
an MSI goes from the PCI bus to the rest of the system (i.e. the CPU(s))
is implementation dependent.

/jeff
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