[ath9k-devel] Atheros Throughput with Aggregation & Encryption

[Mahesh Kumar <mkumar@solectek.com>]

We are using the latest driver.
Kernel version is 2.6.13
armeb-linux-uclibc-gcc version 3.4.3, for xscale


charles at thewybles.com wrote:
> What version of the code?
> What version of the linux kernel?
> What compile tool chain?
> What distro? 
>
> Thanks. 
>
> Charles
>
>
> ------Original Message------
> From: Mahesh Kumar
> Sender: ath9k-devel-bounces at lists.ath9k.org
> To: ath9k-devel at lists.ath9k.org
> ReplyTo: mkumar at solectek.com
> Sent: Jul 28, 2008 4:11 PM
> Subject: [ath9k-devel] Atheros Throughput with Aggregation & Encryption
>
> Hello,
>
> We have a critical issue in getting the high throughput, once we enable 
> both the Aggregation (AMPDU) and Encryption (WPA) at the same time. (We 
> are using the AR9160 chipset.)
>
> Our test setup is like this,
>
> [PC1] ---> [Access Point] --> [Client] --> [PC2].
>
> We are sending a 100 Mbps of UDP traffic from PC1 to PC2. The 
> Aggregation (AMPDU) & Encryption are enabled on both "Access point" and 
> the "Client". Very low traffic ( < 1Mbps) is reaching@the PC2, that 
> also occasionally. Most of the traffic is dropped at the Access point 
> itself. When we check the transmit status descriptor at the Access 
> point, it shows , lots of "Tx delimiter under-run error" & " Tx data 
> under-run error".
>
> Once the driver gets "under-run" error, it starts adjusting the Tx FIFO 
> trigger level [TXCFG register, Frame Trigger level], and it finally 
> reaches it's maximum. This register specifies the minimum number of 
> bytes that must be DMAed  into the PCU TXFIFO, before the PCU initiates 
> the frame on the air.
>
> Any idea on why it's happening ?. Are we missing any special kind of 
> configuration ?. Or is there any known issue when we enable both 
> Aggregation (AMPDU) and encryption simultaneously ?.
>
> The same setup is working, if we disable the Encryption ( getting around 
> 95.7 Mbps). Also the encryption alone is working, without the 
> Aggregation, though we are getting a degraded performance ( max around 
> 30 Mbps.)
>  
>
> Thanks in advance,
> Mahesh.
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