On Jun 11, 2010, at 11:53 AM, Marcel Moolenaar wrote: > > On Jun 11, 2010, at 10:47 AM, Scott Long wrote: > >> On Jun 11, 2010, at 11:44 AM, Marcel Moolenaar wrote: >>> >>> On Jun 11, 2010, at 10:37 AM, Scott Long wrote: >>>> >>>> I'm not clear why you even need bounce buffers for RX. The chip supports >>>> 64bit addresses with no boundary or alignment restrictions. >>> >>> As per: >>> /* >>> * All controllers that are not 5755 or higher have 4GB >>> * boundary DMA bug. >>> * Whenever an address crosses a multiple of the 4GB boundary >>> * (including 4GB, 8Gb, 12Gb, etc.) and makes the transition >>> * from 0xX_FFFF_FFFF to 0x(X+1)_0000_0000 an internal DMA >>> * state machine will lockup and cause the device to hang. >>> */ >>> if (BGE_IS_5755_PLUS(sc) == 0) >>> sc->bge_flags |= BGE_FLAG_4G_BNDRY_BUG; >>> >>> and: >>> lowaddr = BUS_SPACE_MAXADDR; >>> if ((sc->bge_flags & BGE_FLAG_40BIT_BUG) != 0) >>> lowaddr = BGE_DMA_MAXADDR; >>> if ((sc->bge_flags & BGE_FLAG_4G_BNDRY_BUG) != 0) >>> lowaddr = BUS_SPACE_MAXADDR_32BIT; >>> /* >>> * Allocate the parent bus DMA tag appropriate for PCI. >>> */ >>> error = bus_dma_tag_create(bus_get_dma_tag(sc->bge_dev), >>> 1, 0, lowaddr, BUS_SPACE_MAXADDR, NULL, >>> NULL, BUS_SPACE_MAXSIZE_32BIT, 0, BUS_SPACE_MAXSIZE_32BIT, >>> 0, NULL, NULL, &sc->bge_cdata.bge_parent_tag); >>> >>> >> >> Noted in previous email. If this restriction is put in the boundary >> attribute, then you'll only bounce the very rare case of an mbuf straddling >> a 4G boundary. > > I agree with you, but I was just giving the facts. I don't even > know if we attempted to use the boundary argument before but > problems forced us to resort to this. >
Thanks to the design limitation of PCIe, the 4GB boundary is a common restriction and should work fine in FreeBSD. Scott _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
