Linus Torvalds wrote:
HOWEVER - that's only true on systems with no other PCI bridges. Even if
you have an Intel NB/SB, what about other bridges in that same system, and
the devices behind them?
Now, I think that a MSI thing should look like a PCI write to a magic
address (I'm really not very up on it, so correct me if I'm wrong), and
thus maybe bridges are bound to get it right, and the only thing we really
need to worry about is the host bridge. Maybe. In that case, it might be
sensible to have a host-bridge white-table, and if we know all Intel
bridges that claim to support MSI do so correctly, then maybe we can just
say "ok, always enable it for Intel host bridges".
That's pretty much the idea behind MSI... it looks like any other PCI
bus transaction, rather than needing a separate pin.
But right now I'm not convinced we really know what all goes wrong. Maybe
it's just broken NVidia and AMD bridges. But maybe it's also individual
devices that continue to (for example) raise _both_ the legacy IRQ line
_and_ send an MSI request.
That reminds me of a potential driver bug -- MSI-aware drivers need to
call pci_intx(pdev,0) to turn off the legacy PCI interrupt, before
enabling MSI interrupts.
So far, MSI history on x86 has always followed these rules:
* it works on Intel
* it doesn't work [well | at all] on AMD/NV
The only thing that has changed recently is that people are trying to
get it working on AMD/NV as well. (Brice Goglin's stuff starting at
6397c75cbc4d7dbc3d07278b57c82a47dafb21b5 in 'git log')
Seems to me this hda-intel driver patch is fallout from
pci_msi_enabled() not failing on enough systems (all AMD/NV?).
Anyway, if you want your master switch, put it there, not in each driver...
Jeff
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
