svn commit: r209026 - in head/sys/ia64: ia64 include
Scott Long
scottl at samsco.org
Fri Jun 11 17:55:11 UTC 2010
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
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