On Thu, 09 Oct 2008 23:32:51 -0700
Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> in ehci_pci_setup()
>
> switch (pdev->vendor) {
> 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.)
> */
> 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;
> }
>
> so that is strange silicon bug for old ck804 and before. dma_mask could be 32bit. but consistent_dma_mask is 31bit
> mcp55 is ok.
Hmm, looks broken hardware...
> >> qlogic qla2xxx and emulex lpfc dma mask and consistent_dma_mask is different...
> >> could have some story for them
> >
> > Check out qla2xxx again. I think that it uses dma_set_mask() to set
> > dma_mask. qla2xxx uses the same value for both dma_mask and
> > consistent_dma_mask.
> >
> > lpfc had better set 64bit to consistent_dma_mask but as I said in the
> > previous mail, not setting consistent_dma_mask doesn't cause any
> > problem. It means that some IOMMUs (uses consistent_dma_mask properly)
> > allocates an address < 4GB in alloc_coherent() and some IOMMUs alloc
> > address > 4GB. lpfc can handle both anyway.
> >
> >
> >> at least gart iommu is honoring the consistent dma mask.
> >> by calling dma_alloc_coherent_mask(dev, flag)
> >
> > Well, that's because I wrote gart's alloc_coherent and introduced
> > dma_alloc_coherent_mask. ;)
>
> oh. it is in tip
Yeah, it's in tip. But the current gart code uses coherent_dma_mask
properly (GART in tip works in the same way as the current
GART). IIRC, other X86 hardware IOMMUs (VT-d, Calgary, AMD) uses
dma_mask in dma_alloc_coherent (AMD in tip uses coherent_dma_mask).
> >> if device could use 64 bit coherent dma mask, that is driver problem...
> >
> > Can you be more specific? As I wrote above, if 64bit-dma-capable
> > devices don't set consistent_dma_mask, we don't have any problem.
>
> then can we remove consistent_dma_mask? just use dma_mask instead for all.
I don't think we can. One architecture needs it. The above usb
chip seems to need it.
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