On Fri, Feb 09, 2007 at 07:36:40AM +0000, Russell King wrote:
> On Fri, Feb 09, 2007 at 02:48:42PM +1100, David Gibson wrote:
> > At present set_irq_handler() and all the existing variants take the
> > desc->lock for the irq in question before adjusting the irq's flow
> > handler. This can cause problems for irq chips for which a given
> > interrupt can be either level or edge depending on what's attached.
>
> Are you sure you need to change the flow handler depending on how
> you program the device?
>
> Since the outset of this design, I've had what are essentially edge
> based interrupt sources using the "level" handlers because they haven't
> had a "broken" edge implementation. By that, I mean that the masking
> is done in such a way that you miss edges when the source is masked.
>
> If you do not miss edges while the source is masked, there's no point
> in having the complexity of the "edge" based handler in the path - it
> buys you nothing. Just use the "level" handler instead.
I see... how terribly obvious.
As far as I know, the 4xx UIC does things correctly, though I don't
have handy any devices with edge interrupts to test it with.
It would still be nice to have this change, so we can use the
lazy-masking from handle_edge_irq(), but I guess I can do without it
for now.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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