From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D47EEB64D7 for ; Wed, 28 Jun 2023 08:27:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234031AbjF1I1I convert rfc822-to-8bit (ORCPT ); Wed, 28 Jun 2023 04:27:08 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:23422 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234027AbjF1IZA (ORCPT ); Wed, 28 Jun 2023 04:25:00 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with both STARTTLS and AUTH (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-128-vlZ0-3KkNdaZvqYiTvu37Q-1; Wed, 28 Jun 2023 09:24:56 +0100 X-MC-Unique: vlZ0-3KkNdaZvqYiTvu37Q-1 Received: from AcuMS.Aculab.com (10.202.163.4) by AcuMS.aculab.com (10.202.163.4) with Microsoft SMTP Server (TLS) id 15.0.1497.48; Wed, 28 Jun 2023 09:24:55 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Wed, 28 Jun 2023 09:24:55 +0100 From: David Laight To: 'Dmitry Antipov' , Larry Finger CC: "linux-wireless@vger.kernel.org" , "Kalle Valo" , Jonas Gorski , "lvc-project@linuxtesting.org" , "stable@vger.kernel.org" Subject: RE: [PATCH] [v2] wifi: b43: fix cordic arithmetic Thread-Topic: [PATCH] [v2] wifi: b43: fix cordic arithmetic Thread-Index: AQHZqQsGGmQjvdKBv0W33H1tLjOZ1K+f3QLw Date: Wed, 28 Jun 2023 08:24:55 +0000 Message-ID: References: <20230627151411.92749-1-dmantipov@yandex.ru> In-Reply-To: <20230627151411.92749-1-dmantipov@yandex.ru> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org From: Dmitry Antipov > Sent: 27 June 2023 16:14 > > In 'lpphy_start_tx_tone()', 'CORDIC_FLOAT((sample.i * max) & 0xFF)' > is invalid because it is (<32-bit> & 0xff) shifted right by 15 bits > and so always evaluates to zero. Looking through brcmsmac's > 'wlc_lcnphy_start_tx_tone()', the result should be masked instead, > i. e. 'CORDIC_FLOAT(sample[i].max) & 0xFF'. > > Fixes: 6f98e62a9f1b ("b43: update cordic code to match current specs") > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Cc: stable@vger.kernel.org > Suggested-by: Jonas Gorski > Signed-off-by: Dmitry Antipov > --- > v2: add Cc: stable and Fixes: (Larry Finger) > --- > drivers/net/wireless/broadcom/b43/phy_lp.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/wireless/broadcom/b43/phy_lp.c b/drivers/net/wireless/broadcom/b43/phy_lp.c > index 0e5c076e7544..e8ef04e509aa 100644 > --- a/drivers/net/wireless/broadcom/b43/phy_lp.c > +++ b/drivers/net/wireless/broadcom/b43/phy_lp.c > @@ -1788,8 +1788,8 @@ static void lpphy_start_tx_tone(struct b43_wldev *dev, s32 freq, u16 max) > for (i = 0; i < samples; i++) { > sample = cordic_calc_iq(CORDIC_FIXED(theta)); > theta += rotation; > - buf[i] = CORDIC_FLOAT((sample.i * max) & 0xFF) << 8; > - buf[i] |= CORDIC_FLOAT((sample.q * max) & 0xFF); > + buf[i] = (u16)((CORDIC_FLOAT(sample.i * max) & 0xFF) << 8); > + buf[i] |= (u16)(CORDIC_FLOAT(sample.q * max) & 0xFF); What are the (u16) casts for? This code is actually called exactly once with max == 100. The .i and .q are the sine and cosine << 16 (signed). The CORDIC_FLOAT() is basically >> 16 (not 15) so the result should be between -100 and +100. The & 0xFF is there to strip the sign. The sin+cos are then packed into a short[] then unpacked to be written to the hardware later. > } > > b43_lptab_write_bulk(dev, B43_LPTAB16(5, 0), samples, buf); Don't open the bag of worms that contains the above :-) David > -- > 2.41.0 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)