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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Bob Copeland <me@bobcopeland.com>
Cc:     Balaji Pothunoori <bpothuno@codeaurora.org>,
        johannes@sipsolutions.net,
        Ashok Raj Nagarajan <arnagara@codeaurora.org>,
        linux-wireless@vger.kernel.org, ath10k@lists.infradead.org
Subject: Re: [PATCH v4 3/3] ath10k: add support for controlling tx power to a station
References: <1553856587-21611-1-git-send-email-bpothuno@codeaurora.org>
        <20190402223709.GB8910@localhost>
Date:   Wed, 18 Sep 2019 16:41:54 +0300
In-Reply-To: <20190402223709.GB8910@localhost> (Bob Copeland's message of
        "Tue, 2 Apr 2019 18:37:09 -0400")
Message-ID: <871rwdbu1p.fsf@kamboji.qca.qualcomm.com>
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Bob Copeland <me@bobcopeland.com> writes:

> On Fri, Mar 29, 2019 at 04:19:47PM +0530, Balaji Pothunoori wrote:
>> From: Ashok Raj Nagarajan <arnagara@codeaurora.org>
>> 
>> This patch will add the support to control the transmit power for traffic
>> to a station associated with the AP.
>> 
>> Underlying firmware will enforce that the maximum tx power will be based
>> on the regulatory requirements. If the user given transmit power is greater
>> than the allowed tx power in the given channel, then the firmware will use
>> the maximum tx power in the same channel.
>> 
>> When 0 is sent to the firmware as tx power, it will revert to the default
>> tx power for the station.
>> 
>> Tested Hardware : QCA9984
>> Tested Firmware : 10.4-3.9.0.1-00013
>
> I tried this on qca9984 with 10.4-3.9.0.2-00040, which claims to support
> this feature, and it didn't seem to work:
>
> - with global tx power limit set to 30 dBm, I started an iperf from station
>   A -> B
>
> - while iperf underway, I did tcpdump on a monitor on B and looked at signal
>   level in radiotap, in this case around -75 dBm
>
> - on A, changed the per-sta txpwr limit for B to something (tried as low as
>   1 dBm).  verified via printk that it went through to the driver / firmware
>   command and reported no error
>   -> result: signal level unchanged
>
> - on A, changed the global tx power limit to 1 dBm
>   -> result: signal level dropped to ~ -95 dBm
>
> Reading the description above, now I'm wondering if the txpower is
> max(sta-power,global-power)?  If so, that seems a bit unintuitive to me,
> or at least isn't what I hoped for.  I'd prefer to have per-sta power
> setting override the global power.

Balaji, please reply to Bob's questions. I missed this thread while
applying v5, sorry Bob.

-- 
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches