[PATCH] yenta: irq-routing for TI bridges...again

Russell King rmk+pcmcia at arm.linux.org.uk
Sat Mar 13 09:46:15 GMT 2004

On Sat, Mar 13, 2004 at 01:13:59AM +0100, Daniel Ritz wrote:
> On Friday 12 March 2004 21:32, Pavel Roskin wrote:
> > I'm a bit concerned that the driver is "trying to fix" something the
> > second time when PCI interrupts should be working already.  See below.
> doesn't look so good. fixed. the fallback-to-pci code needs to be outside
> of the serial stuff (anyway, to handle the setting for parallel non working
> ISA interrupts right). 

Indeed - some of these registers (MFUNC for instance) are shared between
function 0 and function 1 in dual-socket bridges.  If we've setup and
registered stuff for function 0, we shouldn't really be tweaking it
while probing function 1.

> > And now we come to the need to define the scope of the problems we want to
> > address.
> > 
> > 1) Do we want to deal with mfunc being random at startup or we only want
> > to deal with 0 and/or certain specific values?  Can we just ignore the
> > original value if we determine that it's incorrect?
> don't trust it, trust the probe.

I'd suggest "trust it unless proven by probe that it is wrong" is the
correct approach - you'll never be able to probe the correct MFUNC 
value of 0xfba97543 in my laptop for instance.

> > 3) Do we want to try to enable ISA interrupts if PCI interrupts are
> > working and ISA interrupts are not?
> don't know...why not?

I suspect probing them may be hazardous - sure it can be tried, but I
think it should be treated as a separate problem to the present one.
I think it'll need a lot more testing on more hardware.

Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
                 2.6 Serial core

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