iwlwifi for 7260 card: DMA memory allocation fails

[Christian Menard]

Hello Josef,

unfortunately I still have no possibility to get LOG output via serial, I only 
can print the LOG to screen and I'm too lazy to type the full log ;). However, 
I did some investigation into the problem. The device is stopped because of 
this error:

> dma_map_single: virtual address b008a78 not registered for DMA, called from: 
1070bfc
> def_error: Error sending BT_CONFIG: enqueu_hcmd failed: -12

Where dma_map_single is called by enqueu_hcmd. So the problem is related to 
DMA,

Btw, I also tried to increase the memory quota to ensure there is enough 
memory.

Ask if you need any more info from the logs, then I will type or do a photo)

Cheers
Christian

On Monday 01 December 2014 16:50:14 Josef Söntgen wrote:
> Hallo Christian,
> 
> On 12/01/14 16:32, Christian Menard wrote:
> > I'm experimenting with the new iwlwifi driver on a device with 7260 card.
> > I
> > enabled support for this card as mentioned in the release notes and added
> > the corresponding firmware file iwlwifi-7260-8.ucode. Unfortunately the
> > driver is not working out of the box for this card.
> > 
> > The problem breaks down to a failure during DMA memory allocation. Here an
> > 
> > excerpt from wifi_drv's log:
> >> Slab too large 131072 reqested 86032 cached 0
> >> dma alloc 81920 failed
> >> Slab too large 131072 reqested 105428 cached 0
> >> dma alloc 101316 failed
> >> ....
> >> Slab too large 131072 reqested 86032 cached 0
> >> dma alloc 81920 failed
> >> Slab too large 262144 reqested 175072 cached 0
> >> dma alloc 170960 failed
> > 
> > I naively increased maximum slab size by setting SLAB_STOP_LOG2 in
> > lxc_emul.cc> 
> > to 20. Then failure changes to:
> >> Failed to get slab for 262144
> >> dma alloc: 170960 failed
> > 
> > So as it appears such a large slab cannot be allocated. Why is that? What
> > would be the right way (tm) to resolve this issue?
> 
> Could you please attach the whole log file? These error messages are
> normally harmless — the driver tries to load the firmware all at once
> and falls back to loading the it in smaller chunks if that is not
> possible. I suspect the issue lies elsewhere.
> 
> Regards
> Josef
> 
> 
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