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Date:   Sat, 17 Nov 2018 08:36:28 +0000
From:   Priit Laes <plaes@plaes.org>
To:     Michael =?iso-8859-1?Q?B=FCsch?= <m@bues.ch>
Cc:     Kees Cook <keescook@chromium.org>,
        Jia-Ju Bai <baijiaju1990@gmail.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        Larry Finger <Larry.Finger@lwfinger.net>,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        Colin Ian King <colin.king@canonical.com>,
        Arend van Spriel <arend.vanspriel@broadcom.com>,
        Varsha Rao <rvarsha016@gmail.com>,
        linux-wireless@vger.kernel.org, b43-dev@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/3] b43: Use cordic algorithm from kernel library
Message-ID: <20181117083628.sm6juvz75kiargz4@plaes.org>
References: <cover.c0b1738f3f06bbf87f4ad3200ece93322a5f135f.1542219596.git-series.plaes@plaes.org>
 <d93962cdc5a32fe99e6e5a25172920d28583aa6a.1542219596.git-series.plaes@plaes.org>
 <20181114194628.0f485637@wiggum>
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On Wed, Nov 14, 2018 at 07:46:28PM +0100, Michael B?sch wrote:
> On Wed, 14 Nov 2018 20:27:52 +0200
> Priit Laes <plaes@plaes.org> wrote:
> 
> > Kernel library has a common cordic algorithm which is identical
> > to internally implementatd one, so use it and drop the duplicate
> > implementation.
> 
> 
> In v2 of the series it has been said that:
> 
> Arend van Spriel <arend.vanspriel@broadcom.com> wrote:
> > I recall doing a comparison between the algorithms and thought I put 
> > that in the original commit message. However, it is not there. It is not 
> > exactly the same as in b43 so there are difference for certain angles, 
> > most results are the same however. This implementation is slightly more 
> > accurate on the full scale.
> 
> 
> That's not my definition of "identical".
> 
> Please do not apply this patch without doing a thorough regression test
> on actual b43 LP hardware.

Indeed, there's a big discrepancy in the results of both algorithms.

Here's the test script:
https://gist.github.com/plaes/284993a4fc65e0926d0628a11f0cf874

So at current state, this is self-NAK from me too and this patch should
be dropped.

> 
> -- 
> Michael