Question on setting tx-power in ath10k.

Ben Greear greearb at
Wed Feb 25 15:02:51 PST 2015

On 02/25/2015 01:15 PM, Ben Greear wrote:
> On 02/25/2015 11:55 AM, Adrian Chadd wrote:
>> Yeah I remember this stuff. ath9k did the same thing too; it subtracts
>> TX power based on 2-chain and 3-chain; assuming that the max transmit
>> power in the EEPROM is actually the 3-chain value so it can get the
>> per-chain transmit power.
>> Thing is, whenever I actually looked at the output on a spectrum
>> analyser, the target power differed from what the card was rated at by
>> exactly 3 and 5 dBm respectively. Grr.
>> In FreeBSD I look at the number of configured chains for that TX
>> attempt and set the TX power cap appropriately per-packet. Grr.
> We have a spectrum analyzer now, but I'm not sure if I can even force
> the NIC to run at a specific HT or VHT rate, so not so sure how to
> test the changes properly.
> Either way, even if I adjust this as I am trying to do now
> (on a per-rate basis based on number of chains that rate uses)
> the min/max power restraints stay in place, so it should still
> be fine as far as regulations are concerned.
> Thanks for the info.

I have uploaded a new beta CT firmware with this change.  If anyone has
time to do some detailed testing on it, that would be welcome.

I've added a release notes text file to the same directory as well, for
those who have asked.


> Ben
>> -adrian
>> On 25 February 2015 at 10:24, Ben Greear <greearb at> wrote:
>>> I have added some debugging in my CT firmware based on 10.1.467, and I have noticed
>>> that anything below 5db is treated as zero by the firmware.  This is due primarily to
>>> subtracting a fixed amount based on the NIC's configured chainmask.
>>> I am guessing this is not entirely correct, since at /b rates, for instance, we
>>> will be transmitting on only a single chain, so it does not matter how many
>>> chains the hardware has?
>>> Anyone have any insight on how this stuff is *supposed* to work?
>>> If you have access to firmware source, plz contact me off the mailing list
>>> and I can provide more details about the code that looks broken.
>>> Thanks,
>>> Ben
>>> --
>>> Ben Greear <greearb at>
>>> Candela Technologies Inc
>>> _______________________________________________
>>> ath10k mailing list
>>> ath10k at

Ben Greear <greearb at>
Candela Technologies Inc

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