Messages in this thread | | | Subject | Re: [patch] PCI: disable MSI on more ATI NorthBridges | From | Krzysztof Halasa <> | Date | Tue, 23 Oct 2007 01:40:18 +0200 |
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Jeff Garzik <jeff@garzik.org> writes:
> Note that INTX_DISABLE is a recent addition to PCI.
It's PCI 2.3.
> 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.
> 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 [...]
> But unfortunately that is rather irrelevant, since we see these > out-of-spec devices in the field today.
Right. -- Krzysztof Halasa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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