Question on setting tx-power in ath10k.

Ben Greear greearb at
Wed Feb 25 13:15:53 PST 2015

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.


> -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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