Question on setting tx-power in ath10k.

Adrian Chadd adrian at
Wed Feb 25 11:55:11 PST 2015

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.


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
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