Bruno,

I don't doubt your findings, although I must admit that it's 
disappointing.  I had naively hoped was reading an undocumented 
register.  Calibration initially starts at every 1s, but later drops 
down to every 30s.  The more accurate we can make this the better.  
Storing the noise per packet as we are still makes sense, and the call 
to ath_hal_get_channel_noise() does exactly what you propose to do 
outside the HAL so I don't see any reason to change it.  If it doesn't 
read any registers, it can't be much more expensive than invoking a 
local pointer.  If it is, then I suggest there is something else it is 
doing that we need to understand before we discard it.  The noise level 
samples are used by several management tools and utilities for 
histograms and such.  I was sure I had seen better than 1s resolution in 
the actual values of noise read by these things, but I believe you.  
That said, I think what we have is working well enough.  What advantage 
would we get by changing it?

bruno randolf wrote:
> hello!
>
> today did some tracing with madwifi on AR5212/PHY5111/2111 and AR5414 based 
> cards and i noticed that the function ath_hal_get_channel_noise() does not 
> actually read any registers. that means it must return the noise value from 
> some HAL internal state.
>
> that also means calling this function in ath_uapsd_processtriggers() to 
> update 
> the noise per rx descriptor (in IRQ context btw!) is superfluous.
>
> i'm not quite sure (yet) where the noise is actually read from, probably 
> ath_hal_calibrate() - unless the HAL reads the noise from some register i 
> don't know about. so it would be enough to update ic->ic_channoise after that 
> and only read that value in ath_uapsd_processtriggers(), especially since 
> ath_uapsd_processtriggers() is in IRQ context and should be as efficient as 
> possible. since the noise is not updated that often anyways, we might even 
> consider to move it into the rx tasklet.
>
> bruno
>
>
>
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