[ath9k-devel] Enhancing ath9k for embedded systems

[Felix Fietkau <nbd@openwrt.org>]

On 2009-12-15 2:18 PM, Ayee Goundan wrote:
> I apologize for the delay. Please use Sasi Subramaniam as your first
> point of contact for OpenWRT related questions, while cc'ing Senthil
> Balasubramanian. Sasi will coordinate appropriate help within the
> organization to provide as quick a response as possible.

Hi Sasi,

I've quoted my initial problem description below. Please let me know if
you have any questions about my details of my test setup.

Thanks,

- Felix

>> I'm running OpenWrt with our Linux 2.6.30 based kernel and ath9k from
>> compat-wireless on two identical devices based on AR7240 and AR9283
>> (Python+Merlin). The devices are 'Rocket M5' by Ubiquiti Networks.
>> One of them is configured to run as an AP, the other one is
>> connected to
>> it as STA.
>>
>> The main problem that I have been unable to track down so far is that
>> whenever I run traffic through those two devices, I get very bad
>> throughput (max. 60 mbit/s, mostly only 50 mbit/s).
>> Rate control stats show that the rate in use is mostly 216
>> MBit/s, with
>> a low packet error rate (fluctuating between 0 and 7%).
>> Packet captures
>> from an external device confirm this. Aggregation is
>> definitely working
>> properly, and the CPU load on both devices usually stays well
>> below 50%.
>>
>> I also ran similar tests with ath9k on completely different hardware,
>> with exactly the same issues. The other hardware combinations that I
>> tested were Intel IXP4xx based boards with AR5416, AR9160 and AR9220
>> based cards. The kernel that I used on those boards was 2.6.28.
>>
>> I can rule out issues with the Kernel or the Ethernet driver, since a
>> modified version of the Carrier LSDK driver is performing well in the
>> same setup (I included the carrier driver in the same firmware build
>> that I tested ath9k with).
>>
>> The weird part to this is that whenever I run the same set of
>> tests with
>> an older MacBook as STA against one of the ath9k devices as AP, I get
>> more than 95 MBit/s in both directions (limited by the Ethernet
>> connection speed). I also ran the same tests with a Ralink
>> RT2870 device
>> instead of the MacBook card, with equally good results.
>>
>> I've spent a considerable amount of time trying to track this
>> issue down
>> (including comparing register traces against a working
>> driver), with no
>> promising lead so far, so I'd appreciate any help from your side.