Re: [Madwifi-devel] radar detection sensitivity

[Michael T. <mik...@ap...>]

> I saw two portion of code that might be used to detect radar:
> 1. Upon receiving an interrupt, the interrupt status can be checked with 
> the AR5K_INT_RXPHY bits. However, since the interrupt status is ORed 
> with the interrupt mask, this bit is never set. Is it what you called 
> interruptRXPHY? Did you made changes to the source code to enable this 
> interrupt?
>   
Correct.  The interrupt mask has to be updated to trigger interrupts for 
any RXPHY error.
> 2. Upon receiving a data packet, ds->ds_rxstat.rs_status is checked for 
> the bits AR5K_RXERR_PHY. In this case, ds->ds_rxstat.rs_phyerr & 0x1f 
> might contain AR5K_PHYERR_RADAR. Is it what you call "radar error code"?
>   
Correct. 
> If so, i think that radar event could be filtered using 
> ds->ds_rxstat.rs_rssi and some predefined threshold?
>   
Yes, but it's not that simple I'm afraid.  The PHY chip does have two 
thresholds for min/max RSSI within which a pulse must fall, as well as 
how much gain drop has to occur , etc... there are several patents from 
Atheros on their detection method that describe the system. 

There is *ALSO* a bit in register 0x9954 that must be enabled to get 
radar detection enabled, and this is supposed to be done in the HAL.  I 
think it's supposed to be done when you enable interference mitigation 
(ATH_CAP_INTMIT I believe). 

I have been unsuccessful in getting the HAL to enable this bit, nor to 
leave it alone... but I've slammed it often enough detection stays 
enabled.  I'm looking for how to configure the PHY chip's RSSI min/max 
thresholds for radar detection (if possible/necessary) and how to get 
the HAL to actually enable it for me.

- M
> Best regards,
> Benoit
>
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