linux-kernel - [PATCH] ASoC: nau8825: use 64-bit arithmetic instead of 32-bit

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Message-ID: <20180704142828.GA11007@embeddedor.com>
Date:   Wed, 4 Jul 2018 09:28:28 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] ASoC: nau8825: use 64-bit arithmetic instead of 32-bit

Add suffix ULL to constant 256 in order to give the compiler complete
information about the proper arithmetic to use.

Notice that such constant is used in a context that expects an
expression of type u64 (64 bits, unsigned) and the following
expression is currently being evaluated using 32-bit arithmetic:

256 * fs * 2 * mclk_src_scaling[i].param

Addresses-Coverity-ID: 1339616 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 sound/soc/codecs/nau8825.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/codecs/nau8825.c b/sound/soc/codecs/nau8825.c
index dc6ea49..b9fed99 100644
--- a/sound/soc/codecs/nau8825.c
+++ b/sound/soc/codecs/nau8825.c
@@ -2016,7 +2016,7 @@ static int nau8825_calc_fll_param(unsigned int fll_in, unsigned int fs,
 	fvco_max = 0;
 	fvco_sel = ARRAY_SIZE(mclk_src_scaling);
 	for (i = 0; i < ARRAY_SIZE(mclk_src_scaling); i++) {
-		fvco = 256 * fs * 2 * mclk_src_scaling[i].param;
+		fvco = 256ULL * fs * 2 * mclk_src_scaling[i].param;
 		if (fvco > NAU_FVCO_MIN && fvco < NAU_FVCO_MAX &&
 			fvco_max < fvco) {
 			fvco_max = fvco;
-- 
2.7.4