From: Nick Kossifidis <mickflemm@gmail.com>
To: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Cc: linux-wireless@vger.kernel.org, ath9k-devel@venema.h4ckr.net
Subject: Re: [PATCH] ath9k: spectral - simplify max_index calculation
Date: Thu, 18 Jun 2015 16:13:18 +0200 [thread overview]
Message-ID: <CAFtRNNy009MVbOpHOWVZMuDAaJzmLed+nhBwgybgSS+hbjU=tQ@mail.gmail.com> (raw)
In-Reply-To: <55829F18.9050807@neratec.com>
2015-06-18 12:36 GMT+02:00 Zefir Kurtisi <zefir.kurtisi@neratec.com>:
> On 06/18/2015 10:43 AM, Nick Kossifidis wrote:
>> max_index is a 6bit signed integer in both cases (sorry for the 5bit
>> typo in the comments), so the current function handles it correctly
>> for both HT20 and dynamic HT20/40 modes (I've tested it extensively).
>> Also you don't handle the negative indices we get from the hardware
>> (you just remove the sign). Have you tested this and if you did on
>> which hardware did you do the test ?
>>
>> 2015-06-16 11:21 GMT+02:00 Zefir Kurtisi <zefir.kurtisi@neratec.com>:
>>> [...]
>>> +/* return the max magnitude from the all/upper/lower bins
>>> + *
>>> + * in HT20: 6-bit signed number of range -28 to +27
>>> + * in HT40: 6-bit unsigned number of range 0 to +63
>>> + * (upper sub-channel index 0 is DC)
>>> + *
>>> + * Correct interpretation of the value has to be done at caller
>>> + */
>
> The comment above is taken from developer NDA documents and should be correct.
> With that, in HT40 mode the max_index value has to be taken as is, while in HT20
> it needs to be shifted to the unsigned range.
>
I have NDA documents as well stating that the indices are from -64 to
63 (-64 to -1, 1 to 63 and 0 is DC), you can check out for yourself
that we get 128bins on dynamic HT20/40, see the header files too:
#define SPECTRAL_HT20_40_NUM_BINS 128
and/or the received packet length. Maybe you are talking about
"static" HT40 (I don't see anything about that on the documents I
have) or something else.
> I used the proposed method with the chirp detector for FFTs provided for long
> radar pulses on an AR9590 (patch posted the same day). Max bin index is used there
> the same way as with spectral, but now I realize my mistake: for chirp detection,
> the relative max_index is sufficient, while for spectral the absolute value is needed.
>
> Toggling the MSB in HT20 shifts the signed values by 32 and leaves the index with
> an offset of 4, therefore the correct operation should be:
> ht20_max_index_absolute = (ht20_max_index ^ 0x20) - 4
>
Have in mind that on earlier chips (I did the testing on an AR9820) we
get corrupted frames sometimes so we also need the sanity check I put
there or else we can end up reading data out of bounds which is pretty
dangerous so please leave the current implementation there as is.
--
GPG ID: 0xEE878588
As you read this post global entropy rises. Have Fun ;-)
Nick
WARNING: multiple messages have this Message-ID (diff)
From: Nick Kossifidis <mickflemm@gmail.com>
To: ath9k-devel@lists.ath9k.org
Subject: [ath9k-devel] [PATCH] ath9k: spectral - simplify max_index calculation
Date: Thu, 18 Jun 2015 16:13:18 +0200 [thread overview]
Message-ID: <CAFtRNNy009MVbOpHOWVZMuDAaJzmLed+nhBwgybgSS+hbjU=tQ@mail.gmail.com> (raw)
In-Reply-To: <55829F18.9050807@neratec.com>
2015-06-18 12:36 GMT+02:00 Zefir Kurtisi <zefir.kurtisi@neratec.com>:
> On 06/18/2015 10:43 AM, Nick Kossifidis wrote:
>> max_index is a 6bit signed integer in both cases (sorry for the 5bit
>> typo in the comments), so the current function handles it correctly
>> for both HT20 and dynamic HT20/40 modes (I've tested it extensively).
>> Also you don't handle the negative indices we get from the hardware
>> (you just remove the sign). Have you tested this and if you did on
>> which hardware did you do the test ?
>>
>> 2015-06-16 11:21 GMT+02:00 Zefir Kurtisi <zefir.kurtisi@neratec.com>:
>>> [...]
>>> +/* return the max magnitude from the all/upper/lower bins
>>> + *
>>> + * in HT20: 6-bit signed number of range -28 to +27
>>> + * in HT40: 6-bit unsigned number of range 0 to +63
>>> + * (upper sub-channel index 0 is DC)
>>> + *
>>> + * Correct interpretation of the value has to be done at caller
>>> + */
>
> The comment above is taken from developer NDA documents and should be correct.
> With that, in HT40 mode the max_index value has to be taken as is, while in HT20
> it needs to be shifted to the unsigned range.
>
I have NDA documents as well stating that the indices are from -64 to
63 (-64 to -1, 1 to 63 and 0 is DC), you can check out for yourself
that we get 128bins on dynamic HT20/40, see the header files too:
#define SPECTRAL_HT20_40_NUM_BINS 128
and/or the received packet length. Maybe you are talking about
"static" HT40 (I don't see anything about that on the documents I
have) or something else.
> I used the proposed method with the chirp detector for FFTs provided for long
> radar pulses on an AR9590 (patch posted the same day). Max bin index is used there
> the same way as with spectral, but now I realize my mistake: for chirp detection,
> the relative max_index is sufficient, while for spectral the absolute value is needed.
>
> Toggling the MSB in HT20 shifts the signed values by 32 and leaves the index with
> an offset of 4, therefore the correct operation should be:
> ht20_max_index_absolute = (ht20_max_index ^ 0x20) - 4
>
Have in mind that on earlier chips (I did the testing on an AR9820) we
get corrupted frames sometimes so we also need the sanity check I put
there or else we can end up reading data out of bounds which is pretty
dangerous so please leave the current implementation there as is.
--
GPG ID: 0xEE878588
As you read this post global entropy rises. Have Fun ;-)
Nick
next prev parent reply other threads:[~2015-06-18 14:13 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-16 9:21 [PATCH] ath9k: spectral - simplify max_index calculation Zefir Kurtisi
2015-06-16 9:21 ` [ath9k-devel] " Zefir Kurtisi
2015-06-18 8:43 ` Nick Kossifidis
2015-06-18 8:43 ` [ath9k-devel] " Nick Kossifidis
2015-06-18 10:36 ` Zefir Kurtisi
2015-06-18 10:36 ` [ath9k-devel] " Zefir Kurtisi
2015-06-18 14:13 ` Nick Kossifidis [this message]
2015-06-18 14:13 ` Nick Kossifidis
2015-06-18 15:11 ` Zefir Kurtisi
2015-06-18 15:11 ` [ath9k-devel] " Zefir Kurtisi
2015-06-18 15:59 ` Nick Kossifidis
2015-06-18 15:59 ` [ath9k-devel] " Nick Kossifidis
2015-06-18 15:34 ` Nick Kossifidis
2015-06-18 15:34 ` [ath9k-devel] " Nick Kossifidis
2015-06-18 15:46 ` Nick Kossifidis
2015-06-18 15:46 ` [ath9k-devel] " Nick Kossifidis
2015-06-18 16:40 ` Zefir Kurtisi
2015-06-18 16:40 ` [ath9k-devel] " Zefir Kurtisi
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