kern/179269: [ath] [AR9285] RX antenna diversity is not functioning correctly; breaks single-antenna designs

[adrian chadd]

>Number:         179269
>Category:       kern
>Synopsis:       [ath] [AR9285] RX antenna diversity is not functioning correctly; breaks single-antenna designs
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jun 03 19:10:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     adrian chadd
>Release:        FreeBSD-10
>Organization:
>Environment:
>Description:
This is applicable to -9 and -8 as well.

The AR9285 is a 1x1 design with a twist on "classic" style antenna diversity. The MAC can choose:

* RX on antenna 1 or 2;
* RX on both, by using a "mixer configuration" to mix the signals from both antennas a specific way;
* RX on both, by selecting either antenna 1 or 2 (ie, classic diversity) based on signal level;
* RX on both, by using the above mixer configuration (well two - main and alternate) and selecting one based on signal level

Now, by default, we're only doing RX on a single antenna. The AR_DEF_ANTENNA register controls the static antenna selection if fast diversity isn't enabled.

However! The AR5416 HAL does this:

        /*
         * Preserve the antenna on a channel change
         */
        saveDefAntenna = OS_REG_READ(ah, AR_DEF_ANTENNA);
        if (saveDefAntenna == 0)                /* XXX magic constants */
                saveDefAntenna = 1;

. which means RX will only occur on antenna #2 if antenna diversity is disabled.

So in one antenna solutions (antenna #1 / Main is connected) the unit will TX through the antenna, but RX through the unconnected port.

>How-To-Repeat:

* AR9285
* Connect an antenna to antenna #1
* do NOT connect an antenna to antenna #2
* Try being a station for a while
>Fix:
This workaround (for the AR5416, I guess) needs to be made conditional.

Fast and slow antenna diversity should be enabled as well. I'll go through the code and figure out why that isn't enabled.

>Release-Note:
>Audit-Trail:
>Unformatted: