[ath9k-devel] ath9k:Descriptor(or Per packet) based TPC

[Anu Krishnamoorthy <anuramku@yahoo.com>]

Hi Luis,
?
Thanks for the reply. I believe the "sc" struct and the curtxpow, config.txpowlimit are used to store/configure the global power(iwconfig <interface> txpower <val>) for all the packets that are transmitted using a wireless interface.
?
If you want a differential treatment(use specific power for only certain packets) then per packet/descriptor based TPC has to be used. The descriptor portion is part of the "transmit buffer" (File:ath9k/xmit.c, Function: ath_tx_start_dma, Argument: bf, attribute bf_desc). There are functions to set various fields of this descriptor struct such as
ath9k_hw_set11n_txdesc, ath9k_hw_set11n_ratescenario (File: ath9k/mac.c) that currently do not make use of these fields. 

When I tried to populate the tx power control fields(for a 5416 chip based card)
within the descriptor for every packet buffer, I did not find any effect from the power setting(used the received signal strength for measurement) when I used a sniffer. 
Hence I am wondering is more need to be done to force the other functional blocks with the HW to read and apply these descriptors? How to force the HW process the descriptors?

Thanks,
Ramkumar.

--- On Tue, 11/24/09, Luis R. Rodriguez <lrodriguez@atheros.com> wrote:


From: Luis R. Rodriguez <lrodriguez@atheros.com>
Subject: Re: [ath9k-devel] ath9k:Descriptor(or Per packet) based TPC
To: "Anu Krishnamoorthy" <anuramku@yahoo.com>
Cc: "ath9k-devel at lists.ath9k.org" <ath9k-devel@lists.ath9k.org>
Date: Tuesday, November 24, 2009, 12:29 PM


On Tue, Nov 24, 2009 at 09:00:58AM -0800, Anu Krishnamoorthy wrote:
> Hi,
> 
> I had implemented descriptor based TPC(per packet TPC) for ath9k by setting the various TxPower control fields within the Tx Descriptor (set11n_txdesc) for the Tx frames. From my testing, for some reason the Tx power values present in the descriptor are not applied by the hardware(I am using ar5416 based card). In contrast, if "iwconfig txpower" (in spite of the known bug) is used(forced to apply by down/up'ing the interface) the power change is noticed from the sniffer.
>? ? ???Is any additional setup(transmit queue, txdesc interrupt or hardware setup) needs to be done to force the hardware read and process the tx descriptors? Appreciate if any one could shed more light on it or share their own experience if they had tried to implement this feature.
> 
> Thanks,
> Ramkumar.

The tx power setting was just set on the sc struct, we likely need a reset so
that when tx power is changed it actually takes effect. There may be an easier
way but I haven't had time to look at this yet.

? Luis