Re: [PATCH] pata_cmd640: CMD640 PCI support

[Sergei Shtylyov]

Alan Cox wrote:
> > > > +    if (t.active > 16)
> > > > +        t.active = 16;
> >
> >    Erm, clamping active time is not a right thing to do. Right thing to do 
> > was to bail out. I didn't do it in the legacy driver rewrite though...

> As far as I can work out its a "can't happen"

> > > > +        pci_read_config_byte(pdev, ARTIM23, &reg);

> >    It's not even expensive, it may be just unsafe.

> You have to serialize the channels and idle both so its very expensive -
> or is that what you meant by unsafe.

   I meant that the address setup timing should always match that of a slower 
device -- *no* switching.

> > > > +    /* CMD640 detected, commiserations */
> > > > +    pci_write_config_byte(pdev, 0x5C, 0x00);

> > > magic number

> >   Indeed, completely undocumented. And I don't even see it in the legacy 
> > driver...

> Should be 0x5B which is still undocumented. Will fix that.

   Ah, that's what became DRWTIM3 in the later chips?

> >    It's used to be a well known fact (soon after Intel put that chip on their 
> > motherboards :-) that PCI0640 may return bad data on command block reads if 
> > another channel has data port I/O going on. That's why the interrupts needed 
> > to be disabled during PIO in the legacy driver (and the channels serialized).

> I was under the impression this was only the situation with the
> FIFO/readahead logic enabled, as with the RZ1000 ?

   Sorry, I mixed up with RZ1000 for the Intel's case -- memory fade. :-<

> Can you clarify that at all ?

   Yeah, it was happening with IDE prefetch of course...

> Alan

WBR, Sergei
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