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Subject: Re: [PATCH v3 1/4] dt-bindings: net: wireless: mt76: add power-limits
 node
To:     Rob Herring <robh@kernel.org>
Cc:     linux-wireless@vger.kernel.org, devicetree@vger.kernel.org,
        evelyn.tsai@mediatek.com, Shayne Chen <shayne.chen@mediatek.com>
References: <20200715130134.34988-1-nbd@nbd.name>
 <20200721030416.GA3448943@bogus>
From:   Felix Fietkau <nbd@nbd.name>
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Date:   Tue, 21 Jul 2020 20:17:50 +0200
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On 2020-07-21 05:04, Rob Herring wrote:
> On Wed, Jul 15, 2020 at 03:01:34PM +0200, Felix Fietkau wrote:
>> This subnode can be used to set per-rate tx power limits either per
>> country code / regdomain or globally.
>> These limits are typically provided by the device manufacturers and are
>> used to limit sideband emissions and stay within regulatory limits
>> 
>> Co-developed-by: Shayne Chen <shayne.chen@mediatek.com>
>> Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
>> Signed-off-by: Felix Fietkau <nbd@nbd.name>
>> ---
>> v3:
>>  - fix S-o-b order
>> v2:
>>  - merge 802.11ax rate changes from Shayne's patch
>>  - document txs-delta property
> 
> This is an extensive enough change that I think it needs to be in schema 
> format.
Okay, I will convert the existing file soon and then add these changes
afterwards.

>>  .../bindings/net/wireless/mediatek,mt76.txt   | 59 +++++++++++++++++++
>>  1 file changed, 59 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/net/wireless/mediatek,mt76.txt b/Documentation/devicetree/bindings/net/wireless/mediatek,mt76.txt
>> index ab7e7a00e534..e4859c974ef4 100644
>> --- a/Documentation/devicetree/bindings/net/wireless/mediatek,mt76.txt
>> +++ b/Documentation/devicetree/bindings/net/wireless/mediatek,mt76.txt
>> @@ -36,6 +36,7 @@ Optional nodes:
>>  - led: Properties for a connected LED
>>    Optional properties:
>>      - led-sources: See Documentation/devicetree/bindings/leds/common.txt
>> +- power-limits: contains per-regdomain/channel rate power limit subnodes
>>  
>>  &pcie {
>>  	pcie0 {
>> @@ -76,3 +77,61 @@ wmac: wmac@18000000 {
>>  
>>  	power-domains = <&scpsys MT7622_POWER_DOMAIN_WB>;
>>  };
>> +
>> +
>> +Subnodes of power-limits:
>> +
>> +Properties:
>> +- country: One or more country codes, as used by the cfg80211 regdomain code
> 
> What are the values? cfg80211 is a Linux thing and doesn't belong in 
> bindings.
I'll change the description to leave out cfg80211.
It's a simple alpha2 country code.

>> +- regdomain: "FCC", "ETSI" or "JP"
> 
> These aren't implied by the country code?
You use either country code or regdomain.

>> +If neither country, nor regdomain is specified, the power limits node is used
>> +as a fallback when no other subnode matches.
>> +
>> +Subnodes txpower-2g, txpower-5g:
>> +
>> +Properties:
>> +- channels: pairs of first and last channel number
> 
> What's the range in terms of channel numbers and pairs?
802.11 channel numbers (0-255)

>> +- cck: 4 half-dBm per-rate power limit values
>> +- ofdm: 8 half-dBm per-rate power limit values
>> +- mcs:
>> +	sets of per-rate power limit values for 802.11n/802.11ac rates for
>> +	multiple channel bandwidth settings.
>> +	Each set starts with the number of channel bandwidth settings for
>> +	which the rate set applies, followed by either 8 (MT7603/MT7628) or
>> +	10 (all other chips) power limit values.
>> +	The order of the channel bandwidth settings is: 20, 40, 80, 160 MHz.
> 
> The example only has 2 sets, so which channels are they?
The format is <number_of_sets set_data>, so a set starting with <3 ...>
would contain the values for 20, 40 and 80 MHz and you'd add another one
with <1 ...> to describe 160 MHz.
Sets often contain the same data for multiple channel bandwidths, so
this reduces duplication.

>> +- ru:
>> +	sets of per-rate power limit values for 802.11ax rates for multiple
>> +	channel bandwidth or resource unit settings.
>> +	Each set starts with the number of channel bandwidth or resource unit
>> +	settings for which the rate set applies, followed by 12 power limit
>> +	values. The order of the channel resource unit settings is:
>> +	RU26, RU52, RU106, RU242/SU20, RU484/SU40, RU996/SU80, RU2x996/SU160.
> 
> Could be 8-bit? Doesn't really matter much for the example, but what's 
> the worst/typical case?
Yes, 8 bit would also work.

>> +- txs-delta: half-dBm power delta for different numbers of antennas (1, 2, ...)
>> +
>> +
>> +power-limit example:
>> +
>> +power-limits {
>> +	r0 {
> 
> What's 'r0'? Not documented.
> 
>> +		regdomain = "FCC";
>> +		txpower-5g {
>> +			r1 {
> 
> What's 'r1' and 'r2'? Not documented.
You add an arbitrary number of subnodes (I just used r0, r1, ...)
containing rules with the documented properties.

- Felix