RE: [PATCH V5 2/3] ARM64 LPC: Add missing range exception for special ISA

Gabriele Paoloni
2016-11-09T14:52:05Z

> -----Original Message-----
> From: One Thousand Gnomes [mailto:gnomes@lxorguk.ukuu.org.uk]
> Sent: 09 November 2016 13:55
> To: Arnd Bergmann
> Cc: Mark Rutland; Yuanzhichang; catalin.marinas@arm.com;
> will.deacon@arm.com; robh+dt@kernel.org; bhelgaas@google.com;
> olof@lixom.net; linux-arm-kernel@lists.infradead.org;
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> liviu.dudau@arm.com; zourongrong@gmail.com; John Garry; Gabriele
> Paoloni; zhichang.yuan02@gmail.com; kantyzc@163.com; xuwei (O);
> marc.zyngier@arm.com
> Subject: Re: [PATCH V5 2/3] ARM64 LPC: Add missing range exception for
> special ISA
>
> > I think it is a relatively safe assumption that there is only one
> > ISA bridge. A lot of old drivers hardcode PIO or memory addresses
>
> It's not a safe assumption for x86 at least. There are a few systems
> with
> multiple ISA busses particularly older laptops with a docking station.

Mmmm right...now the point is that this kind of special devices appearing
as a special ISA bus will probably never appear on x86 platforms (I guess).

So maybe it is a safe assumption because of this...?

Thanks

Gab

>
> > when talking to an ISA device, so having multiple instances is
> > already problematic.
>
> PCMCIA devices handle it themselves so are ok. I'm not clear how the
> dual
> PIIX4 configuration used in the older IBM laptop docks actually worked
> so
> I assume the transaction went out of both bridges and providing one of
> them responded the other kept silent as you simply stuffed the card
> into
> the dock and it worked.
>
> Alan