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Date:      Thu, 22 Mar 2001 10:45:31 -0500 (EST)
From:      Robert Watson <rwatson@FreeBSD.org>
To:        Soren Schmidt <sos@freebsd.dk>
Cc:        Takahashi Yoshihiro <nyan@FreeBSD.org>, sos@FreeBSD.org, jkh@FreeBSD.org, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/etc MAKEDEV
Message-ID:  <Pine.NEB.3.96L.1010322104159.10372D-100000@fledge.watson.org>
In-Reply-To: <200103221540.QAA67077@freebsd.dk>

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On Thu, 22 Mar 2001, Soren Schmidt wrote:

> It seems Robert Watson wrote:
> > 1) It may be that we need a seperate "MAKEDEV all" for each architecture
> > 
> > 2) Someone :-) needs to fix ATA to provide the support you need for PC98,
> >    as I keep being assured that WD is marching towards destruction.
> 
> Well, not much I can do here due to lack of that platform, but I'll be
> gald to help, however I havn't heard anything about this from the PC98
> gang... 

Ok, well, we need to get some communication going, and perhaps we can
finally get rid of WD in 5.0-RELEASE :-).

> > It's useful to note that the primary source of problems with AD that I
> > have observed is overly agressive use of DMA instead of PIO for devices
> > that don't support it.  I wonder if that's something we could be doing
> > better?
> 
> This has been solved in -current, as the ata driver now check the
> ata.ata_dma tunable for wether or not DMA should be used, ie it is
> settable from the loader before the system boot, its then later settable
> with atacontrol pr device.  It would have benn so much easier if devices
> told the real deal on wether they support DMA or not... 

I guess in my mind ata.ata_dma isn't a solution per se, it's a work
around.  From the sounds of it, there may not be a solution.  Is it
possible that some of the DMA-related failures are controller-related, and
we could have a list of suspect controllers that cause ata.ata_dma to get
appropriately tuned?  I've experienced ATA problems on a number of
machines, most notably my main file server, which prevented me from
updating for a long time.  Life got a lot better after appropriate
tweaking of dma->pio, but still seem to get intermittent:

ad0: WRITE command timeout tag=0 serv=0 - resetting
ata0: resetting devices .. done
ad0: timeout waiting for DRQ - resetting
ata0: resetting devices .. done
ad0: timeout waiting for DRQ - resetting
ata0: resetting devices .. done
ad0: timeout waiting for DRQ - resetting
ata0: resetting devices .. done

messages (very infrequently -- once every few days).  My atamodes are:

hw.atamodes: pio,dma,dma,pio,

Robert N M Watson             FreeBSD Core Team, TrustedBSD Project
robert@fledge.watson.org      NAI Labs, Safeport Network Services



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