MT7612 - TX Power Issue + Solution

[CR-Ryan]

We have had TX power issues on the 7612 for ages - and no amount of goofing with the wireless config helped. Setting a TX value anywhere between 11 - 30dBm made no difference to the actual observed signal strength.

Here are some examples of what we tried:
Setting various values for "option txpower"
Trying all of the available htmodes
Trying different country codes
Trying various channels (using "iw list" as a reference)
We are on 73edb2

So we (myself and @slthomason) had a contractor write this patch for us:

002-debugfs-api-for-target-power.txt

We recognize that it's a bit of a hack, but it works, and has been for sometime. When we include that patch in our build, we see a ~9dBm improvement in observed signal strength. (-63 vs -72dBm @ 15m)

Also, without our tx patch in place, iwconfig shows this:

wlan1 IEEE 802.11 Mode:Master Tx-Power=9 dBm
RTS thr:off Fragment thr:off
Power Management:off

So it appears to be hitting some kind of wall around 9 - 11dBm in stock form.

We were hoping to see this issue fixed correctly, so that we don't have to use a band-aid.

[barhom]

May we know which target it is you are testing?

[slthomason]

MT7621. Particularly ZBT-WE1326 and ZBT-WG3526

[mastum]

We have had TX power issues on the 7612 for ages - and no amount of goofing with the wireless config helped. Setting a TX value anywhere between 11 - 30dBm made no difference to the actual observed signal strength.

I tried now with dir-860l b1 and xiaomi 3g and it works correctly.
It seems a specific problem of ZBT-WE1326 and ZBT-WG3526.

[barhom]

@nbd168
You have one of these ZBT devices. What is your comment regarding this patch?

[Mushoz]

Is this a related problem? If not, please let me know so I can open a new issue. I am using a Dir-860l.

When I double-check whether my regulatory domain is correctly set to The Netherlands, we can see that this is correct:

root@LEDE:~# iw reg get
global
country NL: DFS-ETSI
	(2402 - 2482 @ 40), (N/A, 20), (N/A)
	(5170 - 5250 @ 80), (N/A, 20), (N/A), NO-OUTDOOR, AUTO-BW
	(5250 - 5330 @ 80), (N/A, 20), (0 ms), NO-OUTDOOR, DFS, AUTO-BW
	(5490 - 5710 @ 160), (N/A, 27), (0 ms), DFS
	(5725 - 5875 @ 80), (N/A, 13), (N/A)
	(57000 - 66000 @ 2160), (N/A, 40), (N/A)

I can see that on channels 100-140 I should be able to use up to 27 dBm:

		Frequencies:
			* 5180 MHz [36] (20.0 dBm)
			* 5200 MHz [40] (20.0 dBm)
			* 5220 MHz [44] (20.0 dBm)
			* 5240 MHz [48] (20.0 dBm)
			* 5260 MHz [52] (20.0 dBm) (radar detection)
			* 5280 MHz [56] (20.0 dBm) (radar detection)
			* 5300 MHz [60] (20.0 dBm) (radar detection)
			* 5320 MHz [64] (20.0 dBm) (radar detection)
			* 5500 MHz [100] (27.0 dBm) (radar detection)
			* 5520 MHz [104] (27.0 dBm) (radar detection)
			* 5540 MHz [108] (27.0 dBm) (radar detection)
			* 5560 MHz [112] (27.0 dBm) (radar detection)
			* 5580 MHz [116] (27.0 dBm) (radar detection)
			* 5600 MHz [120] (27.0 dBm) (radar detection)
			* 5620 MHz [124] (27.0 dBm) (radar detection)
			* 5640 MHz [128] (27.0 dBm) (radar detection)
			* 5660 MHz [132] (27.0 dBm) (radar detection)
			* 5680 MHz [136] (27.0 dBm) (radar detection)
			* 5700 MHz [140] (27.0 dBm) (radar detection)
			* 5745 MHz [149] (13.0 dBm)
			* 5765 MHz [153] (13.0 dBm)
			* 5785 MHz [157] (13.0 dBm)
			* 5805 MHz [161] (13.0 dBm)
			* 5825 MHz [165] (13.0 dBm)

However, setting anything higher than 20 dBm still shows only 20 dBm in Luci:

Mode: Master | SSID: XXXX
BSSID: XX:XX:XX:XX:XX:XX | Encryption: WPA2 PSK (CCMP)
Channel: 100 (5.500 GHz) | Tx-Power: 20 dBm
Signal: -28 dBm | Noise: 0 dBm
Bitrate: 300.0 Mbit/s | Country: NL

Setting the tx power to something lower than 20 does correctly work, so it's not the setting of power itself that seems bugged:

Mode: Master | SSID: XXXXX
BSSID: XX:XX:XX:XX:XX:XX | Encryption: WPA2 PSK (CCMP)
Channel: 100 (5.500 GHz) | Tx-Power: 19 dBm
Signal: -34 dBm | Noise: 0 dBm
Bitrate: 144.4 Mbit/s | Country: NL

[Kherby]

I have the same problem with my DIR-860L @ OpenWRT 18.06rc1.

> root@860L-AP1:~# iw list | grep -i dbm
>                         * 2412 MHz [1] (20.0 dBm)
>                         * 2417 MHz [2] (20.0 dBm)
>                         * 2422 MHz [3] (20.0 dBm)
>                         * 2427 MHz [4] (20.0 dBm)
>                         * 2432 MHz [5] (20.0 dBm)
>                         * 2437 MHz [6] (20.0 dBm)
>                         * 2442 MHz [7] (20.0 dBm)
>                         * 2447 MHz [8] (20.0 dBm)
>                         * 2452 MHz [9] (20.0 dBm)
>                         * 2457 MHz [10] (20.0 dBm)
>                         * 2462 MHz [11] (20.0 dBm)
>                         * 2467 MHz [12] (20.0 dBm)
>                         * 2472 MHz [13] (20.0 dBm)
>                         * 5180 MHz [36] (20.0 dBm)
>                         * 5200 MHz [40] (20.0 dBm)
>                         * 5220 MHz [44] (20.0 dBm)
>                         * 5240 MHz [48] (20.0 dBm)
>                         * 5260 MHz [52] (20.0 dBm) (radar detection)
>                         * 5280 MHz [56] (20.0 dBm) (radar detection)
>                         * 5300 MHz [60] (20.0 dBm) (radar detection)
>                         * 5320 MHz [64] (20.0 dBm) (radar detection)
>                         * 5500 MHz [100] (26.0 dBm) (radar detection)
>                         * 5520 MHz [104] (26.0 dBm) (radar detection)
>                         * 5540 MHz [108] (26.0 dBm) (radar detection)
>                         * 5560 MHz [112] (26.0 dBm) (radar detection)
>                         * 5580 MHz [116] (26.0 dBm) (radar detection)
>                         * 5600 MHz [120] (26.0 dBm) (radar detection)
>                         * 5620 MHz [124] (26.0 dBm) (radar detection)
>                         * 5640 MHz [128] (26.0 dBm) (radar detection)
>                         * 5660 MHz [132] (26.0 dBm) (radar detection)
>                         * 5680 MHz [136] (26.0 dBm) (radar detection)
>                         * 5700 MHz [140] (26.0 dBm) (radar detection)
>                         * 5745 MHz [149] (13.0 dBm)
>                         * 5765 MHz [153] (13.0 dBm)
>                         * 5785 MHz [157] (13.0 dBm)
>                         * 5805 MHz [161] (13.0 dBm)
>                         * 5825 MHz [165] (13.0 dBm)

So first of all it should be 27dBm @ channel 100-140 in my country and i'm using channel 100 right now but the Tx Power is still @20dBm and a manuel change doesn't work either.... It's really weird !
Hopefully this will be fixed soon...

[barhom]

Has this been incorporated ?
@nbd168

[psyborg55]

this half-assed solution should not be incorporated anywhere. mt76 chip max output is 23.5dBm and even at full power you need hell of a calibration and offload routines that this driver don't provide. this could help in a case your device has ext RF components which the mentioned devices do not have at least according to logs and wiki images of the board (so the bug is somewhere else) but even in such a case that is not a proper way of setting output power to these chips and can only result in further performance degradation

[slthomason]

We initially introduced it as a "hack". However, the power, range, and throughput all dramatically go up when we ad this patch. I am all ears on how to do this. Spencer

…

On Sun, Jul 8, 2018 at 3:04 PM psyborg55 ***@***.***> wrote: this half-assed solution should not be incorporated anywhere. mt76 chip max output is 23.5dBm and even at full power you need hell of a calibration and offload routines that this driver don't provide. this could help in a case your device has ext RF components which the mentioned devices do not have at least according to logs and wiki images of the board (so the bug is somewhere else) but even in such a case that is not a proper way of setting output power to these chips and can only result in further performance degradation — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#172 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AB0TcrCqWCHnI3OGY2P90owGkHEJVkbkks5uEoHUgaJpZM4UCHHX> .

[psyborg55]

then you have dramatically buggy board as i've said and need to look elsewhere (you did check eeprom?). on average boards this would cause problems.

[nbd168]

From what I can see, the vendor driver also has some code to allow boosting the tx power beyond the EEPROM values. However, I think simply exposing this via debugfs is too risky. In my opinion, an acceptable solution would be to allow adding a power offset or overriding the target power via device tree

[psyborg55]

overriding the target power via device tree would be better solution

[Mushoz]

I am not sure I am following. So the fact "iw list" shows 27 dBm on some channels, but unable being able to set anything higher than 20 dBm is not a bug? Or am I misunderstanding things?

[Kherby]

With an older 17.01 snapshot build i saw 24dBm @5ghz at LUCI.
But with the latest 17.01 snapshot build (r3918) it's locked to 20dBm when using a DFS channel where 27dBm would be allowed...

Mode: Master | SSID: 
BSSID:  | Encryption: WPA2 PSK (CCMP)
Channel: 100 (5.500 GHz) | Tx-Power: 20 dBm
Signal: -58 dBm | Noise: 0 dBm
Bitrate: 585.1 Mbit/s | Country: FR

Wiphy phy0
        max # scan SSIDs: 4
        max scan IEs length: 2247 bytes
        max # sched scan SSIDs: 0
        max # match sets: 0
        max # scan plans: 1
        max scan plan interval: -1
        max scan plan iterations: 0
        Retry short limit: 7
        Retry long limit: 4
        Coverage class: 0 (up to 0m)
        Available Antennas: TX 0 RX 0
        Supported interface modes:
                 * IBSS
                 * managed
                 * AP
                 * AP/VLAN
                 * monitor
                 * mesh point
        Band 2:
                Capabilities: 0x1ff
                        RX LDPC
                        HT20/HT40
                        SM Power Save disabled
                        RX Greenfield
                        RX HT20 SGI
                        RX HT40 SGI
                        TX STBC
                        RX STBC 1-stream
                        Max AMSDU length: 3839 bytes
                        No DSSS/CCK HT40
                Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
                Minimum RX AMPDU time spacing: 4 usec (0x05)
                HT TX/RX MCS rate indexes supported: 0-15
                VHT Capabilities (0x000001b0):
                        Max MPDU length: 3895
                        Supported Channel Width: neither 160 nor 80+80
                        RX LDPC
                        short GI (80 MHz)
                        TX STBC
                VHT RX MCS set:
                        1 streams: MCS 0-9
                        2 streams: MCS 0-9
                        3 streams: not supported
                        4 streams: not supported
                        5 streams: not supported
                        6 streams: not supported
                        7 streams: not supported
                        8 streams: not supported
                VHT RX highest supported: 0 Mbps
                VHT TX MCS set:
                        1 streams: MCS 0-9
                        2 streams: MCS 0-9
                        3 streams: not supported
                        4 streams: not supported
                        5 streams: not supported
                        6 streams: not supported
                        7 streams: not supported
                        8 streams: not supported
                VHT TX highest supported: 0 Mbps
                Frequencies:
                        * 5180 MHz [36] (20.0 dBm)
                        * 5200 MHz [40] (20.0 dBm)
                        * 5220 MHz [44] (20.0 dBm)
                        * 5240 MHz [48] (20.0 dBm)
                        * 5260 MHz [52] (20.0 dBm) (radar detection)
                        * 5280 MHz [56] (20.0 dBm) (radar detection)
                        * 5300 MHz [60] (20.0 dBm) (radar detection)
                        * 5320 MHz [64] (20.0 dBm) (radar detection)
                        * 5500 MHz [100] (27.0 dBm) (radar detection)
                        * 5520 MHz [104] (27.0 dBm) (radar detection)
                        * 5540 MHz [108] (27.0 dBm) (radar detection)
                        * 5560 MHz [112] (27.0 dBm) (radar detection)
                        * 5580 MHz [116] (27.0 dBm) (radar detection)
                        * 5600 MHz [120] (27.0 dBm) (radar detection)
                        * 5620 MHz [124] (27.0 dBm) (radar detection)
                        * 5640 MHz [128] (27.0 dBm) (radar detection)
                        * 5660 MHz [132] (27.0 dBm) (radar detection)
                        * 5680 MHz [136] (27.0 dBm) (radar detection)
                        * 5700 MHz [140] (27.0 dBm) (radar detection)
                        * 5745 MHz [149] (disabled)
                        * 5765 MHz [153] (disabled)
                        * 5785 MHz [157] (disabled)
                        * 5805 MHz [161] (disabled)
                        * 5825 MHz [165] (disabled)
        valid interface combinations:
                 * #{ IBSS } <= 1, #{ managed, AP, mesh point } <= 8,
                   total <= 8, #channels <= 1, STA/AP BI must match, radar detec                                                                                                              t widths: { 20 MHz (no HT), 20 MHz, 40 MHz, 80 MHz }

        HT Capability overrides:
                 * MCS: ff ff ff ff ff ff ff ff ff ff
                 * maximum A-MSDU length
                 * supported channel width
                 * short GI for 40 MHz
                 * max A-MPDU length exponent
                 * min MPDU start spacing
        Device supports VHT-IBSS.

[camelcamro]

is this also related to 2,4GHZ ?
and is there the same situation, that it is not supported to setup TX power ?

[slthomason]

This patch (hack) is just for the mt7612 (5g)

…

On Mon, Jul 9, 2018, 7:41 PM camelcamro ***@***.***> wrote: is this also related to 2,4GHZ ? and is there the same situation, that it is not supported to setup TX power ? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#172 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AB0TcjyxNDltv0VqMNSGZb9l2nZRu9zFks5uFBRDgaJpZM4UCHHX> .

[xavier83]

any progress on this issue?

[xavier83]

@slthomason do you think I'm having the same issue (#199) described here?

[nbd168]

Please try the latest version, it should work better now

[storm1er]

Hi,

Could this issue cause this kind of problem?
https://forum.openwrt.org/t/rpi4-and-netgear-a6210-mt7612u-long-distance-problem/78682

As soon as I am at 15m (~50 feets) away from the router, my devices disconnect instantly without any reason, the quality connection is good (like 4/5 before disconnect)