Messages in this thread | | | Date | Tue, 23 Oct 2007 06:13:49 -0400 | From | Jeff Garzik <> | Subject | Re: [patch] PCI: disable MSI on more ATI NorthBridges |
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Krzysztof Halasa wrote: > Jeff Garzik <jeff@garzik.org> writes: > >> Note that INTX_DISABLE is a recent addition to PCI. > > It's PCI 2.3.
Yes.
>> Older PCI devices >> support neither MSI nor INTX-disable, so make sure such devices don't >> creep into your sample. > > MSI has been introduced by PCI 2.2 (and thus PCI-X 1.0) so there may > be devices with MSI but without INTx-disable bit. I guess I have some > early PCI-X hardware with MSI but I don't know if they have INTx-disable > bit and I can't currently test that. > And it probably doesn't matter.
Time will tell :)
>> In general it is documented that INTX_DISABLE should apply only to >> INTx# so devices that disable MSI based on that bit are out of spec. > > The wording is: > 10: This bit disables the device from asserting INTx#. A value of 0 > enables the assertion of its INTx# signal. A value of 1 disables the > assertion of its INTx# signal. This bit's state after RST# is 0. Refer > to Section 6.8.1.3 for control of MSI. > > So strictly speaking it mandates disabling/enabling INTx but says > nothing about other things (e.g. MSI). Some common sense dictates > it shouldn't disable MSI, I guess. > > The "MSI Enable" description doesn't leave any doubt: > 0: MSI Enable: If 1, the function is permitted to use MSI to request > service and is prohibited from using its INTx# pin [...]
Right. I was merely describing the end result, the union of that language as it applies to the kernel.
Jeff
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