Hi all,

I've encountered a problem with my AMD 890FX based system
and linux-2.6.35.10 (x86_64 platform).

After activating the option "IOMMU" in the mainboard's BIOS
setup, the onboard P-ATA controller "JMicron Technology Corp.
JMB361 AHCI/IDE (rev 02)" puts itself back in the PIO mode.
When loading the module, the kernel reports:

  pata_jmicron 0000:06:00.1: BMDMA: failed to set dma mask, \
                             falling back to PIO

This results, as expected, in a much too low data throughput
between the system and the optical drives connected to the
P-ATA controller.

As soon as I deactivate IOMMU in BIOS setup, the P-ATA channel
runs in the DMA mode again. The S-ATA controllers don't seem
to be affected.

My question is: Is this a known behavior? Are there any
things I have to consider when activating IOMMU (which seems
to be AMD-Vi) on an 890FX based system? Is it a problem of
the chipset and/or the controller or is it related to a
problem in the libata area?

Some information about the affected system:

 - Mainboard:    ASUS M4A89TD Pro/USB3
 - BIOS version: 1101 (most recent version)
 - Chipset:      AMD 890FX
 - Processor:    AMD Phenom 1090T
 - Memory:       4 x 4 GB (Kingston KVR1333D3E9S/4G)
 - Distribution: openSUSE 11.3
 - Kernel:       2.6.35.10 (from "kernel.org"), x86_64

Earlier versions of 2.6.35.x are affected, too. I haven't
tested other kernel versions besides 2.6.35.x, yet.

If you need further information (log files, information from
"/proc", lspci, and so on), please let me know.

Thank you very much in advance for any hint!

Best regards,
Steffen
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(CC'd linux-ide, Joerg)


This condition occurs when the PCI API cannot set the PCI device's DMA 
mask to the 32-bit value
	#define ATA_DMA_MASK            0xffffffffULL

That is an unusual failure for such a modern system, which certainly can 
handle 32-bit masks like that, one would think.

	Jeff



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Luckily I have exactly the same motherboard under my desk. It shows the
same issue. The problem is that the PCI device of the PATA controler
(4:00.1 in my case) is not described in the IVRS ACPI table. So the
IOMMU driver does not feel responsible for it and the dma_supported()
call on this device will fail. This also makes pci_set_dma_mask() fail
on this device. So it comes down to a BIOS bug. I look into it to find a
workaround.

	Joerg

-- 
AMD Operating System Research Center

Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632

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[ message continues ]

Hi Joerg,



Thank you.

Beside a possible work-around, do you think, it makes sense to
report the problem to ASUS as the straight way should be to have
a correct IVRS table for the board?

Kind regards,
Steffen
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[ message continues ]

Hi Steffen,


Sure, that makes sense. Probably they fix their BIOS, but I wouldn't
count on it. But it is worth a try.

Regards,

	Joerg

-- 
AMD Operating System Research Center

Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632

--

[ message continues ]