linux-kernel - Re: Disabling DMA with ICH10?

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Message-ID: <m3bpku3peg.fsf@intrepid.localdomain>
Date:	Tue, 29 Sep 2009 14:29:27 +0200
From:	Krzysztof Halasa <khc@...waw.pl>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	"Lennart Baruschka" <FunFlyer@....net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: Disabling DMA with ICH10?

Arjan van de Ven <arjan@...radead.org> writes:

> a single PIO instruction will NOT be interrupted by an interrupt.
> And can easily take several microseconds (remember: 8Mhz bus
> emulation)

Not that long, there is no emulation there (except for port #80 (hex?)
and similar). Normal 33 MHz access. But it's still slow, of course -
every access takes at least 4(?) bus cycles (IIRC: address, initiator
ready, device selected, target ready). No bursts (at least on typical
x86 hw).

Of course ICH10 AHCI isn't connected with PCI 33/32 bus.

Anyway: PIO = bad idea.
-- 
Krzysztof Halasa
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