Re: Driver: PCIe: 'pci_map_sg' returning invalid bus address?

From: Evan Lavelle
Date: Wed Aug 04 2010 - 07:22:50 EST

FUJITA Tomonori wrote:
Made some progress here. The problem is that this is 32-bit PAE kernel, so 'dma_addr_t' is 64-bit. However, I have a 32-bit PCIe card, so I need a 32-bit dma_addr_t. How do I do this? In other words, how do I handle 32-bit PCI cards on PAE or 64-bit systems? My code sets the DMA mask to 32 bits but this is *not* sufficient:

pci_set_dma_mask(my_dev, DMA_32BIT_MASK)

It doesn't work on x86_32 kernel if your driver doesn't work with the
block layer or the network subsystem.

Sorry, not sure that I understand this. Are you saying that I can't set a DMA mask on x86_32 unless I have a block or network driver?

If your driver can't handle 64bit DMA, you need bounce buffer.

The problem is not that I can't handle 64-bit DMA in the driver, but that the PCI card can't do 64-bit DMA. I tell the kernel this by calling 'pci_set_dma_mask' with a 32-bit mask, but it appears to be ignoring my request and then giving me a 64-bit dma_addr_t for the 32-bit PCI card.

Thanks -

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