#1659: Periodic Calibration must disable DMA engine during calibration
----------------------------------+-----------------------------------------
Reporter: mtaylor | Owner: mtaylor
Type: defect | Status: new
Priority: major | Milestone:
Component: madwifi: driver | Version: trunk
Resolution: | Keywords:
Patch_attached: 0 |
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Old description:
> The HAL doesn't disable the DMA engine when doing periodic calibration.
> Periodic calibration actually floats the tx antenna connection while the
> DMA engine is transmitting concurrently. This causes some very weak
> packets to go out. We need to work around this by disabling transmission
> during calibration, and possibly moving the calibration logic so that it
> happens when the transmission queue is empty and actually causes
> transmissions to be requeued until the calibration is finished. This
> would actually make more sense, as the calibration is for transmission
> and is ok to do when not transmitting and in between transmissions.
>
> From Karol Kowalik:
>
> "Thanks a lot for your response. In the mean time I have also identified
> that these strange power drops are caused by the calibration.
>
> Thus, commenting call to HAL function "ath_hal_calibrate" stops these
> strange power drops. However, I have read in Atheros patent (Titled:
> "Method and system for noise floor calibration and receive signal
> strength detection") that during calibration the antenna is in an open
> position or in the Rx position, when calibrating for the
> temperature/environmental changes. This disconnected antenna would
> explain the power drops. However, I was thinking that the card should not
> be allowed to transmit any frames during the calibration procedure.
> However, in my case it looks like it is indeed sending frames. I'm only
> not sure if it is an error or is it intentional?" - Karol Kowalik
>
> Thanks go to Karol Kowalik for isolating and reporting this defect!
New description:
The HAL doesn't disable the DMA engine when doing periodic calibration.
Periodic calibration actually floats the tx antenna connection while the
DMA engine is transmitting concurrently. This causes some very weak
packets to go out. We need to work around this by disabling transmission
during calibration, and possibly moving the calibration logic so that it
happens when the transmission queue is empty and actually causes
transmissions to be requeued until the calibration is finished. This
would actually make more sense, as the calibration is for transmission and
is ok to do when not transmitting and in between transmissions.
From Karol Kowalik:
{{{
#!blockquote
Thanks a lot for your response. In the mean time I have also identified
that these strange power drops are caused by the calibration.
Thus, commenting call to HAL function "ath_hal_calibrate" stops these
strange power drops. However, I have read in Atheros patent (Titled:
"Method and system for noise floor calibration and receive signal strength
detection") that during calibration the antenna is in an open position or
in the Rx position, when calibrating for the temperature/environmental
changes. This disconnected antenna would explain the power drops. However,
I was thinking that the card should not be allowed to transmit any frames
during the calibration procedure. However, in my case it looks like it is
indeed sending frames. I'm only not sure if it is an error or is it
intentional? - Karol Kowalik
}}}
Thanks go to Karol Kowalik for isolating and reporting this defect!
--
Ticket URL: <http://madwifi.org/ticket/1659#comment:3>
madwifi.org <http://madwifi.org/>
Multiband Atheros Driver for Wireless Fidelity
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