Re: Fatal DMA error problem with netbook and BCM4312

[Larry Finger <Larry.Finger@lwfinger.net>]

On 11/22/2009 01:03 PM, Chris Vine wrote:
> On Sat, 21 Nov 2009 00:15:12 +0000
> Chris Vine <chris@cvine.freeserve.co.uk> wrote:
>> WARM BOOT FROM KERNEL WITH WL MODULE INSTALLED
>>
>> The patched kernel makes no change on a warm boot in the sense that
>> if I warm boot after initialising the wireless device with the wl
>> module then the b43 module appears to work correctly, both with and
>> without the patch applied.
>>
>> On the same stress test as mentioned above, I have not been able to
>> induce the DMA errors nor kernel warnings.  It resolutely refuses to
>> do anything except work correctly.
> 
> This is just to say that I have carried out further stress tests today
> after warm booting to an unpatched linux-2.6.32-rc8 kernel with the b43
> driver (on the assumption that unpatched is the least favourable case
> for the driver).  This is a warm reboot from a 2.6.31.6 kernel which had
> the wl driver installed.
> 
> I have created an extended period of high speed traffic on my wireless
> lan and I cannot induce any errors at all with the b43 driver on a warm
> reboot.
> 
> This makes me wonder whether the patch is just (partially) masking the
> problem rather than actually dealing with it.

We know that the wl driver does something to the interface that persists across
a warm boot - we just do not know what. It does not appear to be done in any of
the MMIO traffic - at least I have not seen it in the mmio-trace output. If
anyone has a KVM setup using PCI passthrough, it is possible to trace PCI
configuration traffic?

Have you tried running your system with the patch entitled "[PATCH] b43: Rewrite
DMA Tx status handling sanity checks"? It cleared up some of the problems that I
was seeing with the open-source firmware.

Larry