On Tue, 2007-10-02 at 16:24 +1000, Benjamin Herrenschmidt wrote: > On Tue, 2007-10-02 at 15:58 +1000, Michael Ellerman wrote: > > > Looks allright, just a question tho... what do we do if it fails ? > > Do we > > > try to fallback to a lower number of MSIs ? Or what ? Dead device ? > > > > That's all up to the device driver. In theory the driver could try again > > with a lower count - but that might require extra logic in the driver to > > handle shared irq handlers etc. In practice I think the current drivers > > will just fail. > > Question is badly phrased.. I meant something more like... what do we do > if RTAS returns a lower count ? > > That is, we end up with that device with that lower count of MSIs > enabled, we fail at the driver level, do we still somewhat keep track ? > Drivers might assume that means it can use LSIs no ? which may not be > the case... Shouldn't we try to switch back to LSI mode (or does the > RTAS interface doesnt allow it ?)
OK I get you. So: rtas_setup_msi_irqs() detects that it got fewer MSIs than it asked for and returns an error. The generic code (drivers/pci/msi.c) notices the error and calls msi_free_irqs(). That calls back into rtas_teardown_msi_irqs() which disposes of the virq mappings and calls rtas_disable_msi(). rtas_disable_msi() asks firmware to configure 0 MSIs on the device, that hopefully succeeds. AFAIK configuring 0 MSIs is as close as we can get to disabling MSI via RTAS. Perhaps that should also (re)enable INTX? cheers -- Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person
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