Re: [PATCH] pata_cmd640: CMD640 PCI support

From: Alan Cox
Date: Sat Mar 03 2007 - 14:30:44 EST


> >> + 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.

> >> + /* 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.

> 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 ? Can you clarify that
at all ?

Alan
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/