[FS#929] mt7620 abysmal wifi performance

[LEDE Bugs]

The following task has a new comment added:

FS#929 - mt7620 abysmal wifi performance
User who did this - pmgp (mgondium)

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At this point, trunk won't go past ~50 Mbps @HT40 and the radio will go mute if more than one device connects to the AP (but still show on scans).
Changing channel requires a device restart: issuing "wifi" just makes it go mute as above.
Ocasional "queue full" errors show up on log, as in the original report.

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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=929#comment3214