[PATCH] ath10k: fix system hang at qca99x0 probe on x86 platform

[Michal Kazior]

On 19 July 2016 at 18:53, Ben Greear <greearb at candelatech.com> wrote:
> On 07/19/2016 09:13 AM, Adrian Chadd wrote:
[...]
>> Try allocating WMI memory with GFP_DMA32. The way it currently is
>> working in linux is that caling dma map ends up allocating iommu slots
>> to map that 64 bit memory back into 32 bit space, /or/ it will end up
>> allocating bounce buffers.
>>
>> The WMI memory alloc routine is being used for the swap space too,
>> which ends up with 700kbyte or more allocated twice - once for the
>> initial alloc, and another for the dma map call.
>>
>> You should try GFP_DMA32 and see if that fixes it. You need contig, <
>> 32 bit physical memory allocated, and bounce buffers are really
>> supposed to be ephemeral.
>
>
> I briefly tested with the GFP_DMA32 and it worked on my 9984 test rig.

Doesn't GFP_DMA32 alter the address space your pointers refer to in a
similar way dma-coherent allocations do (compared to regular
kmalloc+dma-map-single)? This would support my theory about
firmware/hardware getting confused if host mem chunks have some MSBs
set.


Michał