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From:   Dmitry Antipov <dmantipov@yandex.ru>
To:     Larry Finger <Larry.Finger@lwfinger.net>
Cc:     linux-wireless@vger.kernel.org, Kalle Valo <kvalo@kernel.org>,
        Jonas Gorski <jonas.gorski@gmail.com>,
        lvc-project@linuxtesting.org, Dmitry Antipov <dmantipov@yandex.ru>,
        stable@vger.kernel.org
Subject: [PATCH] [v2] wifi: b43: fix cordic arithmetic
Date:   Tue, 27 Jun 2023 18:13:53 +0300
Message-ID: <20230627151411.92749-1-dmantipov@yandex.ru>
In-Reply-To: <ef4750f8-8de5-dbfc-2c0b-3400d30d83e5@lwfinger.net>
References: <ef4750f8-8de5-dbfc-2c0b-3400d30d83e5@lwfinger.net>
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Precedence: bulk

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 <jonas.gorski@gmail.com>
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
---
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);
 	}
 
 	b43_lptab_write_bulk(dev, B43_LPTAB16(5, 0), samples, buf);
-- 
2.41.0