disable 64-bit dma for one PCI slot only?

Scott Long scottl at samsco.org
Mon Jul 18 21:06:47 UTC 2011

On Jul 18, 2011, at 12:02 PM, John Baldwin wrote:
> On Friday, July 15, 2011 6:07:31 pm Mark McConnell wrote:
>> Dear folks,
>> I have two LSI raid cards, one of which (SCSI 320-I) supports 
>> 64-bit DMA when 4GB+ of DDR is present and another which 
>> does not (SATA 150-D) .  Consquently I've disabled 64-bit 
>> addressing for amr devices.
>> I would like to disable 64-bit addressing for the SATA card, but 
>> permit it for the SCSI card.  Is this possible?
> You'd have to hack the driver perhaps to only disable 64-bit DMA for certain 
> PCI IDs.  It probably already does this?

The driver already had a table for determining 64bit DMA based on the PCI ID.  I guess there's a mistake in the table for this particular card.  I think that changing the following line to remove the AMR_ID_DO_SG64 flag will fix the problem:

    {0x1000, 0x1960, AMR_ID_QUARTZ | AMR_ID_DO_SG64 | AMR_ID_PROBE_SIG},

Actually, what's probably going on is that the driver is only looking at the vendor and device id's, and is ignoring the subvendor and subdevice id's that would give it a better clue on the exact hardware in use.  Fixing the driver to look at all 64bits of id info (and take into account wildcards where needed) would be a good project, if anyone is interested.

Btw, I *HATE* the "chip" and "card" identifiers used in pciconf.  Can we change it to emit the standard (sub)vendor/(sub)device terminology?


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