linux-kernel - Re: Limiting DMA speeds for individual IDE drives

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Date:	Wed, 9 Sep 2009 00:46:06 -0600
From:	Thomas Fjellstrom <tfjellstrom@...w.ca>
To:	linux-kernel@...r.kernel.org
Subject: Re: Limiting DMA speeds for individual IDE drives

On Tue September 8 2009, Alan Stern wrote:
> On Tue, 8 Sep 2009, Alan Cox wrote:
> > > I've got a situation where a drive claims to be capable of supporting
> > > UDMA/100, but it's in a noisy environment and gets lots of errors at
> > > that speed.  I'd like to limit it to UDMA/66 or even UDMA/33.
> >
> > That should never occur with a proper cable and I would be concerned the
> > fault might be something more problematic such as speed misconfiguration
> > or an incompatibility. Which driver is in use ?
> 
> The cable indeed is likely to be at fault.  The same drive worked okay
> at the higher speed with a different cable (which unfortunately is
> unavailable for use in the final deployment).  This is using the old
> IDE driver.  Here's an extract from the log, with
> ide-core.ignore_cable=0 specified on the command line:
>

I have just one suggestion. Get a new cable.

> Linux version 2.6.27-gentoo-r10 (root@...se) (gcc version 4.1.2 (Gentoo
>  4.1.2 p1.0.2)) #1 SMP PREEMPT Tue Apr 21 15:06:03 UTC 2009 ...
> Uniform Multi-Platform E-IDE driver
> piix 0000:00:1f.1: IDE controller (0x8086:0x24cb rev 0x02)
> pci 0000:00:1f.1: PCI INT A -> GSI 18 (level, low) -> IRQ 18
> piix 0000:00:1f.1: IDE port disabled
> piix 0000:00:1f.1: not 100% native mode: will probe irqs later
> ide: ignoring cable detection for ide0
>     ide0: BM-DMA at 0xf000-0xf007
> Probing IDE interface ide0...
> hda: STEC MACH-8 SSD, ATA DISK drive
> hda: host max PIO4 wanted PIO255(auto-tune) selected PIO4
> hda: UDMA/100 mode selected
> ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
> ide_generic: please use "probe_mask=0x3f" module parameter for probing all
>  legacy ISA IDE ports ide_generic: I/O resource 0x1F0-0x1F7 not free.
> ide_generic: I/O resource 0x170-0x177 not free.
> hda: max request size: 512KiB
> hda: 60789456 sectors (31124 MB), CHS=16383/255/63
> hda: cache flushes not supported
>  hda: hda1 hda2 hda3
> ...
> hda: dma_intr: status=0x51 { DriveReady SeekComplete Error }
> hda: dma_intr: error=0xc4 { DriveStatusError BadCRC UncorrectableError },
>  LBAsect=14823116, sector=14823116 ide: failed opcode was: unknown
> hda: dma_intr: status=0x51 { DriveReady SeekComplete Error }
> hda: dma_intr: error=0xc4 { DriveStatusError BadCRC UncorrectableError },
>  LBAsect=15133492, sector=15133492 ide: failed opcode was: unknown
> hda: dma_intr: status=0x51 { DriveReady SeekComplete Error }
> hda: dma_intr: error=0xc4 { DriveStatusError BadCRC UncorrectableError },
>  LBAsect=9478100, sector=9478100 ide: failed opcode was: unknown
> Etc.; you get the idea...
> 
> > > The hdparm command should be able to do this but I can't run it until
> > > the system has booted, by which time a bunch of CRC and possibly other
> > > errors have already occurred.  Ideally it should be possible to limit
> >
> > Only the data transfers are CRC protected and at high speed, but noise at
> > low speed would be a real concern as the commands are sent low speed but
> > without protection on PATA devices - so a bit flip can send a DMA to the
> > wrong sector.
> >
> > > the speed starting as early as device detection, but I can't find any
> > > way to do it.  Is there support for such a thing or will I have to hack
> > > it in?
> >
> > You can disallow DMA but not clip DMA to UDMA33 with the old driver. You
> > could disallow DMA at boot and reallow it with a speed set by hdparm in
> > your boot scripts...
> 
> On Tue, 8 Sep 2009, Frederik Deweerdt wrote:
> > Does passing ide=nodma at bootime, and then having init set the DMA at
> > the right speed, would work?
> 
> I'll recommend trying that out.  Thanks to both of you for the advice.
> 
> Alan Stern
> 
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-- 
Thomas Fjellstrom
tfjellstrom@...w.ca
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