linux-kernel - RE: [PATCH] Add quirk to set AHCI mode on ICH boards

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Date:	Mon, 12 Nov 2007 23:27:55 -0800
From:	"Allen Martin" <AMartin@...dia.com>
To:	"Jeff Garzik" <jeff@...zik.org>
Cc:	"Alan Cox" <alan@...rguk.ukuu.org.uk>, "Mark Lord" <liml@....ca>,
	"Riki Oktarianto" <rkoktarianto@...il.com>,
	<linux-kernel@...r.kernel.org>,
	"Greg Kroah-Hartman" <gregkh@...e.de>, <linux-ide@...r.kernel.org>
Subject: RE: [PATCH] Add quirk to set AHCI mode on ICH boards

> Allen Martin wrote:
> > At least for NVIDIA controllers, loading the AHCI driver 
> when the BIOS
> > is set to IDE mode is not recommended by NVIDIA.  Any AHCI 
> workarounds
> > in the BIOS are likely to be disabled when set to IDE mode. 
>  In practice
> 
> What workarounds, if any, are needed?
> 
> We need those in the driver not BIOS anyway, in order to 
> fully support 
> suspend/resume and host controller reset during runtime operation.

What I'm worred about is SMI traps implemented in the SBIOS for AHCI
workarounds that may be disabled when in IDE mode.

> In Linux at least, we have a bunch of open sata_nv issues, so forcing 
> users' interface into AHCI mode as a default future policy seems like 
> the most stable choice on NVIDIA AHCI platforms.

I believe most of the issues with sata_nv have been due to lack of
documentation of ADMA and swNCQ.  The NVIDA AHCI controllers that
operate in IDE mode are straight up PATA emulation ANSI/INCITS 370
interface, no hotplug, no NCQ.  So I would expect there to not be a lot
of issues.

I'm with you that AHCI mode is superior and should be used whenever
possible, but it probably comes as no suprise that almost all the
hardware/BIOS testing is done with Windows, and operating the hardware
in a mode that Windows doesn't (enabling AHCI in classcode 0101) seems
like asking for trouble.

-Allen
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