From: Phillip Susi <psusi@ubuntu.com>
To: AlanWEvans@gmail.com, linux-ide@vger.kernel.org
Subject: Re: ahci: host/target numbers change with detection order
Date: Wed, 21 May 2014 11:16:42 -0400 [thread overview]
Message-ID: <537CC35A.6060505@ubuntu.com> (raw)
In-Reply-To: <CAMFVOoU=nbVSzZPU0eJ6Gy=yFNdWQfctANjfQyVjAp0hJFzDrA@mail.gmail.com>
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On 5/19/2014 4:46 PM, Alan Evans wrote:
> I have a host that is used to process the data on removable
> drives. It is essential to be able to indicate to an operator which
> drives are done and can be removed.
>
> When we were using a HighPoint card that uses sata_mv.ko we could
> count on the results of 'udevadm info -q path -n <dev>'
> representing a single physical port on the card.
>
> I have been testing a new card based on a Marvell 88SE9230
> (ahci.ko) and I find that the scsi host number and corresponding
> target are changing depending on the order drives are attached to
> the system, not based on the port number.
These numbers are assigned on a first come first serve basis, so if
another device initializes first, then it jumps in front. If you want
to know the port number, look in the port_no file of the ata_port.
> Further for some reason in /sys/class/scsi_host I am seeing 8
> hosts created per card where I would expect 4.
Apparently the controller supports 8 ports.
> Does anyone have any thoughts on why the behaviour differs between
> ahci.ko and sata_mv.ko? Is it the chip? The module?
It looks like sata_mv does not support parallel scanning of all ports,
but ahci does. In other words, sata_mv scanned one port at a time, in
order, so they always registered in order, but ahci scans them all at
the same time, so the order they finish in varies.
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next prev parent reply other threads:[~2014-05-21 15:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-19 20:46 ahci: host/target numbers change with detection order Alan Evans
2014-05-21 15:16 ` Phillip Susi [this message]
2014-05-22 19:14 ` Alan Evans
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