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Date: Fri, 6 Mar 2009 12:59:48 -0800
Message-ID: <da824cf30903061259j4a37ab7cneea308c736da469d@mail.gmail.com>
Subject: Re: [PATCH] hpsa: SCSI driver for HP Smart Array controllers
From: Grant Grundler <grundler@google.com>
To: scameron@beardog.cca.cpqcorp.net
Cc: Jens Axboe <jens.axboe@oracle.com>,
       FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
       linux-kernel@vger.kernel.org, mike.miller@hp.com,
       akpm@linux-foundation.org, linux-scsi@vger.kernel.org,
       coldwell@redhat.com, hare@novell.com, iss_storagedev@hp.com
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On Fri, Mar 6, 2009 at 6:38 AM,  <scameron@beardog.cca.cpqcorp.net> wrote:
...
> The command buffers have to be in the first 4GB of memory, as the command
> register is only 32 bits, so they are allocated by pci_alloc_consistent.

Huh?!!
ISTR the mpt2sas driver is indicating it can handle 64-bit DMA masks for
both streaming and control data. I need to double check to be sure of that.


> However, the chained SG lists don't have that limitation, so I think they
> can be kmalloc'ed, and so not chew up and unreasonable amount of the
> pci_alloc_consistent memory and get a larger number of SGs.   ...right?
> Maybe that's the better way to do it.

I thought the driver was tracking this and using the appropriate construct
based on which DMA mask is in effect.

hth,
grant

> -- steve
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