linux-kernel - Re: [PATCH] ide: Fix ata_id_has_dword_io to return DWORD I/O support properly

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Date:	Fri, 19 Dec 2008 00:13:09 +0100
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Sergei Shtylyov <sshtylyov@...mvista.com>,
	Jeff Garzik <jeff@...zik.org>,
	Mario Schwalbe <schwalbe@....tu-dresden.de>,
	linux-kernel@...r.kernel.org,
	Linux IDE mailing list <linux-ide@...r.kernel.org>
Subject: Re: [PATCH] ide: Fix ata_id_has_dword_io to return DWORD I/O support properly

On Thursday 18 December 2008, Alan Cox wrote:
> > OTOH the current patch is safe even for 2.6.28 (based on years of experience
> > with the check that we had in IDE subsystem) and will fix some libata drivers
> > (pata_legacy, pata_qdi and pata_winbond) to use dword IO on >= ATA-2 devices.
> > 
> > [ In reality this a regression fix for IDE -> libata conversion as it is a
> >   huge performance improvement for the above mentioned DMA-less drivers. ]
> 
> The 32bit PIO support is already queued up and went to Jeff a while ago
> so thats all in hand - its btw a big win on some suprising chipset cases
> including Intel ICH chipsets.

It is a not exactly the same issue as the pata_{legacy,qdi,winbond} one
discussed above.  Anyway cool to see another IDE -> libata regression fixed.

> > Jeff, I would like to merge it through IDE tree since the other patch depends
> > on it but if you want to go ahead and push it to Linus earlier feel free to
> > do it (or I can include it into the next IDE fixes pull request if you like).
> 
> Its still broken. You cannot use the version check for versions below 3.

Hmm, this doesn't seem to be a problem w.r.t. to the patch we are discussing
because in such case ata_id_major_version() will just return 0 and the check
will behave in the identical way as it was before the patch.

> I remain unconvinced we should be looking at it anywhere except specific
> pure ISA cycle pass through hardware and thus it belongs as a helper for
> those drivers not as ata_has_mumble stuff as its not ATA - eide_* maybe.

Sure, we can always improve things further later.  However Mario's patch
is _definitely_ an improvement over the _current_ code.  Don't you agree?

[ There are no alternative patches to consider currently so... ]

Thanks,
Bart
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