Re: USB 2.0 ehci failure with large amount of RAM (4GB) on x86_64

[Nathan Becker]

Like I said in my previous message, I am not a kernel developer.  I am
a programmer though, so I thought I'd give your suggestions a try.

I added 1 line to drivers/usb/host/ehci-pci.c which sets the DMA mask,
and now it seems to work with ehci loaded and with 4 GB of RAM.
Unfortunately, I don't really understand what I did.  Perhaps you have
a better idea what this is doing and if it is correct.

case PCI_VENDOR_ID_NVIDIA:
		/* NVidia reports that certain chips don't handle
		 * QH, ITD, or SITD addresses above 2GB.  (But TD,
		 * data buffer, and periodic schedule are normal.)
		 */
		
		dma_set_mask(hcd->self.controller, DMA_31BIT_MASK); /* I added this line */
		
		switch (pdev->device) {
		case 0x003c:	/* MCP04 */
		case 0x005b:	/* CK804 */
		case 0x00d8:	/* CK8 */
		case 0x00e8:	/* CK8S */
			if (pci_set_consistent_dma_mask(pdev,
						DMA_31BIT_MASK) < 0)
				ehci_warn(ehci, "can't enable NVidia "
					"workaround for >2GB RAM\n");
			break;
		}
		break;
	}
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