On Thu, 9 Oct 2008 21:56:33 -0700 "Yinghai Lu" <yinghai@xxxxxxxxxx> wrote: > On Thu, Oct 9, 2008 at 7:40 PM, FUJITA Tomonori > <fujita.tomonori@xxxxxxxxxxxxx> wrote: > > On Thu, 09 Oct 2008 16:05:57 -0700 > > Yinghai Lu <yinghai@xxxxxxxxxx> wrote: > > > >> Grant Grundler wrote: > >> > On Thu, Oct 09, 2008 at 02:51:32PM -0700, Yinghai Lu wrote: > >> >> On Thu, Oct 9, 2008 at 2:35 PM, Matthew Wilcox <matthew@xxxxxx> wrote: > >> >>> Why's that interesting to the sysadmin of the machine? To the driver > >> >>> writer, certainly. But what's the use of it to the people using the > >> >>> machine? > >> > ... > >> >> make linux kernel act like black box as other os? > >> > > >> > I don't understand your reply. > >> > If someone thinks linux is a black box, printing this message won't help them. > >> > > >> could find out easily why some driver doesn't set dma mask correctly. > >> like why > >> qlogic qla2xxx only set consistent to 64bit, > >> emulex lpfc not set consistent to 64bit > > > > IIRC, except for one SGI architecture, coherent_dma_mask is > > meaningless, dma_mask is always equal to coherent_dma_mask. Lots of > > IOMMU implementations ignore coherent_dma_mask and use dma_mask for > > alloc_coherent(). Some drivers doesn't set up coherent_dma_mask. > > ehci_hcd 0000:00:02.1: using 31bit consistent DMA mask > ==> ck804 ehci, is using 31bit for consistent dma mask, at still use > 32 bit for dma mask. ehci_hcd needs to set 31bit to dma_mask, I guess. > 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. ;) > 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. Yes, drivers that have dma_mask < 32bit need to set up consistent_dma_mask. But few devices have dma_mask < 32bit and we can fix them without the information at boot time, I think. > print it out could put them in focus. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
