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MPC512x DMA to PCI dev

DISCUSSION Matteo Fortini 1 participant 2 messages Mar 11, 2009 – Mar 12, 2009

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#0 lore raw

Hi all,
I'm trying to send some data through DMA from a memory buffer to a PCI video card VRAM.

While I got that I need to alloc the src buffer through dma_alloc_coherent, I don't understand which address I should give as the dst address.

I tried both the mapped hw address and an address received from pci_map_single, but even if the DMA transfer completes "correctly", I have the wrong data in the VRAM in the end.

I read about all the PCI DMA manuals, but it seems they are for letting some external DMA device on the PCI bus read/write from/to the main memory.

How do you do that?

Thanks,
Matteo

#1 lore raw

Ok,
I answer to myself, to whomever it may interest: the DMA controller to use is the PCI_DMA controller, and not the generic DMA controller.

Right now, I'm trying to figure out if there's a generic PCI API I can extend to talk to the PCI DMA controller.

Matteo Fortini ha scritto:

Quoted 19 lines

Hi all,
I'm trying to send some data through DMA from a memory buffer to a PCI video card VRAM.

While I got that I need to alloc the src buffer through dma_alloc_coherent, I don't understand which address I should give as the dst address.

I tried both the mapped hw address and an address received from pci_map_single, but even if the DMA transfer completes "correctly", I have the wrong data in the VRAM in the end.

I read about all the PCI DMA manuals, but it seems they are for letting some external DMA device on the PCI bus read/write from/to the main memory.

How do you do that?

Thanks,
Matteo
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