On Jun 11, 2010, at 12:04 PM, Pyun YongHyeon wrote: > On Fri, Jun 11, 2010 at 11:55:07AM -0600, Scott Long wrote: >> 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. > > I guess many PCIe drivers in tree do not explicitly set 4GB > boundary restriction. Isn't it better to set it automatically with > bus_get_dma_tag(9)?
That was exactly the intention of introducing bus_get_dma_tag() and having it inherit attributes from the parent bus. 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"
