linux-kernel - Re: [PATCH] Re: Forcing modes in libata (was: SATA buffered read VERY slow)

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Date:	Sun, 6 Jan 2008 19:08:56 +0100
From:	FD Cami <francois.cami@...e.fr>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Cc:	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Al Boldi <a1426z@...ab.com>, Jeff Garzik <jeff@...zik.org>,
	Zoltan Boszormenyi <zboszor@...aweb.hu>
Subject: Re: [PATCH] Re: Forcing modes in libata (was: SATA buffered read
 VERY slow)

On Sun, 6 Jan 2008 17:27:38 +0100
Bartlomiej Zolnierkiewicz <bzolnier@...il.com> wrote:

> On Sunday 06 January 2008, FD Cami wrote:
> > On Sun, 6 Jan 2008 13:36:09 +0000
> > Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> > 
> > > On Sun, 6 Jan 2008 08:03:31 +0300
> > > > > For now you can boot with libata.dma=1 to select DMA on disks
> > > > > but not CD
> > > > 
> > > > Great, but why isn't this in the documentation?
> > > 
> > > Send patches
> > 
> > patch attached.
> > 
> > Description : Add libata.dma= to Documentation/kernel-parameters.txt
> > 
> > Found documentation in :
> > http://www.mail-archive.com/linux-ide%40vger.kernel.org/msg09849.html
> > http://www.redhat.com/archives/fedora-extras-commits/2007-October/msg04568.html
> > 
> > Signed-off-by: François Cami <francois.cami@...e.fr>
> 
> diff -rU2 linux-2.6.24-rc6/Documentation/kernel-parameters.txt 
> linux-2.6.24-rc6-mine/Documentation/kernel-parameters.txt
> ---
> linux-2.6.24-rc6/Documentation/kernel-parameters.txt        2008-01-06
> 15:58:54.000000000 +0100 +++
> linux-2.6.24-rc6-mine/Documentation/kernel-parameters.txt   2008-01-06
> 16:11:20.000000000 +0100 @@ -883,4 +883,11 @@ C2 power state. 
> +       libata.dma=     [LIBATA] DMA control
> +                       libata.dma=0      Disable all PATA DMA like
> old IDE
> 
> this doesn't seem entirely correct:
> 
> * IDE has "hdx=nodma" so you can disable DMA on per-device basis

I think that libata.dma=1 is designed to behave like 
CONFIG_IDEDMA_ONLYDISK used to. "hdx=nodma" is more fine-grained than
this.

> * is this really limited to PATA?

Alan's original patch took care of PATA. SATA support was added
later by Jeff Garzik. Corrected documentation patch attached.

> +                       libata.dma=1      Disk DMA only
> +                       libata.dma=2      ATAPI DMA only
> +                       libata.dma=3      CF DMA only 

This is also wrong, it should be "libata.dma=4      CF DMA only"
Thanks to Zoltan Boszormenyi <zboszor@...aweb.hu> for catching this
mistake.

Revised patch attached.

Best,

François

View attachment "libata-doc-patch2.txt" of type "text/plain" (847 bytes)