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SubjectRe: [PATCH] ALSA: hda-intel - Disable MSI support by default
On Wed, 15 Nov 2006 14:23:20 -0500
Jeff Garzik <jeff@garzik.org> wrote:

> Stephen Hemminger wrote:
> > On Tue, 14 Nov 2006 23:24:04 -0500
> > Jeff Garzik <jeff@garzik.org> wrote:
> >
> >> David Miller wrote:
> >>> Is this absolutely true? I've never been sure about this point, and I
> >>> was rather convinced after reading various documents that once you
> >>> program up the MSI registers to start generating MSI this implicitly
> >>> disabled INTX and this was even in the PCI specification.
> >>>
> >>> It would be great to get a definitive answer on this.
> >>>
> >>> If it is mandatory, perhaps the driver shouldn't be doing it and
> >>> rather the PCI layer MSI enabling should.
> >
> > pci_enable_msi() calls msi_capability_init() and that disables intx
> > already.
> [...]
> > The driver shouldn't deal with this, pci_disable_msi() does.
>
> Explicit code reference please?
>
> AFAICS the PCI layer only touched INTx bit for PCI-Express devices.

Yeah, why is that? Shouldn't it always be adjusting intx.
Are there are any MSI capable devices on non-PCI express?
Sorry, don't have PCI spec (costs real $$) to check.

--- 2.6.19-rc5.orig/drivers/pci/msi.c 2006-11-15 11:46:23.000000000 -0800
+++ 2.6.19-rc5/drivers/pci/msi.c 2006-11-15 11:46:55.000000000 -0800
@@ -255,10 +255,7 @@
pci_write_config_word(dev, msi_control_reg(pos), control);
dev->msix_enabled = 1;
}
- if (pci_find_capability(dev, PCI_CAP_ID_EXP)) {
- /* PCI Express Endpoint device detected */
- pci_intx(dev, 0); /* disable intx */
- }
+ pci_intx(dev, 0); /* disable intx */
}

void disable_msi_mode(struct pci_dev *dev, int pos, int type)
@@ -276,10 +273,8 @@
pci_write_config_word(dev, msi_control_reg(pos), control);
dev->msix_enabled = 0;
}
- if (pci_find_capability(dev, PCI_CAP_ID_EXP)) {
- /* PCI Express Endpoint device detected */
- pci_intx(dev, 1); /* enable intx */
- }
+
+ pci_intx(dev, 1); /* re-enable intx */
}

static int msi_lookup_irq(struct pci_dev *dev, int type)



--
Stephen Hemminger <shemminger@osdl.org>
-
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