b43: DMA errors with BCM4331 on BCM4706

[Hauke Mehrtens]

On 08/03/2013 07:48 PM, Larry Finger wrote:
> On 08/03/2013 11:55 AM, Michael Büsch wrote:
>> On Sat, 03 Aug 2013 17:28:14 +0200
>> Hauke Mehrtens <hauke at hauke-m.de> wrote:
>>
>>> I used wireshark to see what actually happens and the device send out
>>> beacons and answers to probe requests without problems. I see the
>>> Authentication, Association Request and Association Response frames and
>>
>> That suggests DMA works for some packets and then fails?
>>
>>> Does anybody have any thought on this topic?
>>
>> You should print out more of the DMA values.
> 
> Could it possibly work with short packets, but fail on longer ones?
> 
> Larry
Hi,

Thanks for the hints, in fact it was the size and I got my BCM4331 in
the Access Point connected to a BCM4706 working. The problem was that
the the PCIe controller used a PCIe max request size of 128, we try to
change it in driver_pci_host.c, see "MRRS 512", but that does not get
applied to the hardware, when reading it back it is not set, the Max
payload size is changed. The BCM4331 uses a max request size of 512 by
default and that causes problems. I solved the problem by setting the
max request size to 128 for the BCM4331, pcie_set_readrq(bus->host_pci,
128) and then it worked.

The patch is currently just in OpenWrt [0], I will send the patches to
the mailing list in the next days.

@Rafał If you haven't found a BCM4331, now you can use the one in your
Access Point. ;-)

Hauke

[0]: https://dev.openwrt.org/changeset/37709