Regression in qca99x0 on x86 platform (kernel: 4.7.0-rc1-wt-ath

[Ben Greear]

On 06/02/2016 10:46 AM, Rajkumar Manoharan wrote:
> On 2016-06-02 22:57, Ben Greear wrote:
>> On 06/02/2016 10:20 AM, Manoharan, Rajkumar wrote:
>>> Found a regression in ath.git TOT that system hangs while probing qca99x0 device on x86_64 platform.
>>> It seems the system hangs while DMA mapping of bigger memory chunks. Below are the list of memory
>>> chucks requested by target for qca99x0 during service ready event. This issue is seen only on x86 platform.
>>> No issues are observed on ARM platform (AP148). After reverting below commit able to bring up device on x86.
>>>
>>> Jun  2 17:24:37 rmanohar-arch kernel: idx 0 pool_size 689816 num_units 529 unit_len 1304
>>> Jun  2 17:24:37 rmanohar-arch kernel: idx 1 pool_size 17152 num_units 67 unit_len 256
>>> Jun  2 17:24:37 rmanohar-arch kernel: idx 2 pool_size 68608 num_units 67 unit_len 1024
>>> Jun  2 17:24:37 rmanohar-arch kernel: idx 3 pool_size 274432 num_units 67 unit_len 4096
>>> Jun  2 17:24:37 rmanohar-arch kernel: idx 4 pool_size 107520 num_units 35 unit_len 3072
>>> Jun  2 17:24:37 rmanohar-arch kernel: idx 5 pool_size 6144 num_units 1 unit_len 6144
>>> Jun  2 17:24:37 rmanohar-arch kernel: idx 6 pool_size 865444 num_units 529 unit_len 1636
>>
>> We have seen similar.  But, if we enable VT-d in our BIOS, then it
>> works, at least in
>> our scenarios.  I have not tried putting more than one 99x0 NIC in a
>> system to date, so possibly
>> more than one would cause more issues, and I guess systems without VT-d might
>> fail too...
>>
> Yeah.. But the code should work even on non-VT-d systems. ins't it?

It would be great if it did.

>>> commit b057886524be060021e3cfad0ba8458c850330cd
>>> Author: Felix Fietkau <nbd at openwrt.org>
>>> Date:   Mon Nov 30 19:32:01 2015 +0100
>>>
>>>      ath10k: do not use coherent memory for allocated device memory chunks
>>>
>>>      Coherent memory is more expensive to allocate (and constrained on some
>>>      architectures where it has to be pre-allocated). It is also completely
>>>      unnecessary, since the host has no reason to even access these allocated
>>>      memory spaces
>>>
>>>      Signed-off-by: Felix Fietkau <nbd at openwrt.org>
>>>      Signed-off-by: Kalle Valo <kvalo at qca.qualcomm.com>
>>>
>>>
> Ben,
>
> Can you help to confirm this issue by disabling VT-d and bring up qca99x0? If it freezes, try reverting the patch.

At the time, I bisected to this commit as well, but I decided to just live with it
since it seemed it fixed some other bug and we had a work-around.  My understanding
is that without the patch above, some ARM systems failed to work.

Thanks,
Ben


-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com