Re: [patch 2.5] tg3.c: pci_{save,restore}_extended_state

["Wiedemeier, Jeff" <Jeff.Wiedemeier@hp.com>]

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