iwlwifi for 7260 card: DMA memory allocation fails

[Josef Söntgen]

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