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. 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"
