linux-kernel - Re: [patch 2.6.22-rc6] ATA: add a PCI ID for Intel Santa Rosa PATA controller

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Date:	Mon, 2 Jul 2007 16:36:24 +0200
From:	Chr <chunkeey@....de>
To:	Thorsten Leemhuis <fedora@...mhuis.info>
Cc:	Chuck Ebbert <cebbert@...hat.com>, Jeff Garzik <jeff@...zik.org>,
	IDE/ATA development list <linux-ide@...r.kernel.org>,
	Jason Gaston <jason.d.gaston@...el.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 2.6.22-rc6] ATA: add a PCI ID for Intel Santa Rosa PATA controller

On Monday, 2. July 2007, Thorsten Leemhuis wrote:
> > but Alan Cox wrote:
> > http://www.mail-archive.com/linux-ide%40vger.kernel.org/msg07417.html
> >> Its ich_pata_133 - all the newer chips are.
> 
> Intel afaik never supported Ultra ATA 133 officially in any of the
> mainstream desktop or mobile chipsets.

You're probably right! But, what about Intel's ICH5 and ICH7/7-R (i945, i975)?

see ata_piix.c: line 193ff
	{ 0x8086, 0x24DB, PCI_ANY_ID, PCI_ANY_ID, 0, 0, ich_pata_133 },
[...]
	{ 0x8086, 0x27DF, PCI_ANY_ID, PCI_ANY_ID, 0, 0, ich_pata_133 },

On the other hand, we can leave it, because of a "off-by-one error" in ata_piix.c, 
do_pata_set_dmamode, line ~770:

(the comment is important!)
/*
 * --> UDMA is handled by a combination of clock switching and
 * selection of dividers <---
 * [...]
 */
u_speed = min(2 - (udma & 1), udma);
if (udma == 5)
	u_clock = 0x1000;	/* 100Mhz */ <-- wrong! it's 133Mhz.
else if (udma > 2)
	u_clock = 1;		/* 66Mhz */
else
	u_clock = 0;		/* 33Mhz */

=>
for udma = 6(133MB/s) , we get u_speed=2 and u_clock=1
for udma = 4(66MB/s), we get the "same" values! (u_speed=2 and u_clock=1)

...
so, atleast for ata_piix, UDMA6 and UDMA4 *is* the same, right?

> 
> >> They work even better if you
> >> set them into AHCI mode in the BIOS and then they should "just work" with
> >> recent kernels as the AHCI driver now matches by class.
> > And "Gaston, Jason D" <jason.d.gaston@...el.com> didn't complain about it.
> > it's a "bit" confusing with all "native" AHCI SATA chipset that have to emulate 
> > PATA for compatibility reasons... 
> 
> Well, just FYI: on my Laptop AHCI is enabled and used for the SATA hard
> disk. But the DVD drive still is a pata one afaics (I'm not in front of
> the machine, so I can't check), connected via the pata controller -- so
> for me there is no emulation involved (at least afaics).
> 
I know. I wanted to say something else... but it doesn't really matter
(not every operating system supports AHCI-only controllers by default...)

Thanks, 
	Chr.

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