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Message-ID: <58cb370e0601130616l25e0e25ai6b7d2025d9774eff@mail.gmail.com>
Date: Fri, 13 Jan 2006 15:16:51 +0100
From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
To: Rashkae <rashkae@tigershaunt.com>
Subject: Re: ide-cd turning off DMA when verifying DVD-R
Cc: =?ISO-8859-1?Q?Ville_Syrj=E4l=E4?= <syrjala@sci.fi>,
       Ondrej Zary <linux@rainbow-software.org>,
       Robert Hancock <hancockr@shaw.ca>,
       Volker Kuhlmann <list0570@paradise.net.nz>, Jens Axboe <axboe@suse.de>,
       linux-ide <linux-ide@vger.kernel.org>,
       linux-kernel <linux-kernel@vger.kernel.org>
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On 1/13/06, Rashkae <rashkae@tigershaunt.com> wrote:
> On Fri, Jan 13, 2006 at 10:19:17AM +0100, Bartlomiej Zolnierkiewicz wrote:
>
>
> > On 1/13/06, Volker Kuhlmann <list0570@paradise.net.nz> wrote:
> > > On Fri 13 Jan 2006 17:40:33 NZDT +1300, Robert Hancock wrote:
> > >
> > > > I'm thinking the IDE code is too aggressive in assuming that the failure
> > > >  is because of a DMA problem and disabling it.. Most likely all that's
> > > > happening is the drive is taking a long time to complete the current
> > > > command.
> >
> > What actually happened is that normal command timed out
> > and because of that driver reset the device which caused
> > it to loose DMA:
> >
> > ->ide_atapi_error()
> >     ->ide_do_reset()
> >       ->pre_reset()
> >         ->check_dma_crc()
> >           ->__ide_dma_off()
> >
> > Somebody needs to investigate why __ide_dma_off() is called
> > et all and if we need to restore DMA after reset (don't count ATM
> > on me, I'm buried by bugreports).  Ondrej, could you fill the bug at
> > http://bugzilla.kernel.org so we don't lose it?
>
> Shouldn't whether DMA is restored after reset be governed by keepsettings flag?

settings should always be preserved and keepsettings flag should die

> From the hdparm man page:
>
>       -k     Get/set  the  keep_settings_over_reset flag for the
>               drive.  When this flag is set, the driver will pre­
>               serve  the -dmu options over a soft reset, (as done
>               during the error  recovery  sequence).
>
> I was a little disapointed that this didn't work as advertised.

AFAIR (2.5/2.6 and probably 2.4 also) it never worked w.r.t. to DMA
as documented in hdparm manual.

Bartlomiej