What kind of Linux address must I use to set the SAR reg. of the DMA ctrl ?

What kind of Linux address must I use to set the SAR reg. of the DMA ctrl ?

[Callebaut Benoit]

Hello,
I am writing the code to start a DMA transfer with the built-in DMA controller
of the MPC8245. The purpose is to do Memory to PCI transfers. The PCI part
seems to be OK ( memory of the device is written) the the source address seems
to be wrong since I read 0XFFFFFFFF as data in the device. I tried with bus
and physical address (using virt_to_bus & virt_to_phys functions) but this
doesn't give good results.
So I ask myself which kind of linux address must I use to configure the SAR
register of the Dual channel DMA controller ?

If It works I will post a patch of my work.

Thanks

------------------------------------------------------------------------------
----
Benoit Callebaut
Software Development Engineer
Barco | Control Rooms
Noordlaan 5, 8520 Kuurne, Belgium

Tel 	+32(0)56 36 84 28
Fax 	+32(0)56 36 86 05

mailto:benoit.callebaut@barco.com
http://www.barcocontrolrooms.com


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Re: What kind of Linux address must I use to set the SAR reg. of the DMA ctrl ?

[Matt Porter]

On Wed, May 07, 2003 at 02:52:06AM -0400, Callebaut Benoit wrote:
>
> Hello,
> I am writing the code to start a DMA transfer with the built-in DMA controller
> of the MPC8245. The purpose is to do Memory to PCI transfers. The PCI part
> seems to be OK ( memory of the device is written) the the source address seems
> to be wrong since I read 0XFFFFFFFF as data in the device. I tried with bus
> and physical address (using virt_to_bus & virt_to_phys functions) but this
> doesn't give good results.
> So I ask myself which kind of linux address must I use to configure the SAR
> register of the Dual channel DMA controller ?

Well, there's no special "linux address".  The DMA controller takes
a physical address.  I think you are specifically asking about
configuring the source address register when doing a Mem->PCI
transfer.  In that case, if you are using lowmem system memory as
the source address, then virt_to_phys will generate the correct
physical system memory address.

Regards,
--
Matt Porter
mporter@kernel.crashing.org

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RE: What kind of Linux address must I use to set the SAR reg. of the DMA ctrl ?

[Callebaut Benoit]

Thanks a lot Matt,

now the Memory to memory transfer works but I don't see any data on the PCI
side althought the status register of the DMA controller report no error.
I read that I must use untranslated PCI address if the outbound translation
windows are not enabled (this is my case).
So I suppose I must take the address coming from the PCI detection and the
ioremap following it (those appearing in the log like "kernel :PCI:00:12.0:
Resource 1:bf000000-bf7FFFFF") and not the translated one.
I tried so but only 0XFFFFFFFF appears in the memory of the PCI device.
Is it possible that the snooping or caching issue be the problem ?

Regards,

Benoit Callebaut


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