Skip to contentSkip to conversation

ASoC: nau8824: use 64-bit arithmetic instead of 32-bit

PATCH In review Gustavo A. R. Silva 3 participants 3 messages Jul 5, 2018 – Jul 6, 2018

Subsystems (2)
Sound ASoC
lore
Share & tools
lore

Gustavo A. R. Silva

author
#0 lore raw

PATCH 1/1 ASoC: nau8824: 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: 1432039 ("Unintentional integer overflow")

Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 sound/soc/codecs/nau8824.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
sound/soc/codecs/nau8824.c +1 -1
index 6bd1445..468d514 100644
@@ -1274,7 +1274,7 @@ static int nau8824_calc_fll_param(unsigned int fll_in,
 	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;
Signature · 1 line
2.7.4
maintainer
#1 lore raw

Applied "ASoC: nau8824: use 64-bit arithmetic instead of 32-bit" to the asoc tree

The patch

ASoC: nau8824: use 64-bit arithmetic instead of 32-bit

has been applied to the asoc tree at

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git

All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying to this mail.

Thanks,
Mark

Quoted 1 line

From f7ddff54d0a0f068442414b48bec7f22aa777de7 Mon Sep 17 00:00:00 2001

From: "Gustavo A. R. Silva" <[email protected]>
Date: Thu, 5 Jul 2018 08:06:17 -0500
Subject: [PATCH] ASoC: nau8824: 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: 1432039 ("Unintentional integer overflow")

Signed-off-by Gustavo A. R. Silva <[email protected]>
Signed-off-by Mark Brown <[email protected]>
---
 sound/soc/codecs/nau8824.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
sound/soc/codecs/nau8824.c +1 -1
index 6bd14453f06e..468d5143e2c4 100644
@@ -1274,7 +1274,7 @@ static int nau8824_calc_fll_param(unsigned int fll_in,
 	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;
Signature · 1 line
2.18.0.rc2
#2 lore raw
In reply to Gustavo A. R. Silva
Quoted 20 lines · Gustavo A. R. Silva

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: 1432039 ("Unintentional integer overflow")

Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 sound/soc/codecs/nau8824.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
sound/soc/codecs/nau8824.c +0 -0
index 6bd1445..468d514 100644

sound/soc/codecs/nau8824.c static int nau8824_calc_fll_param(unsigned int fll_in, · line 1277

Quoted 5 lines
sound/soc/codecs/nau8824.c +1 -1
@@ -1274,7 +1274,7 @@ static int nau8824_calc_fll_param(unsigned int fll_in,
        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;

This would be better written as fvco = (256 * 2 *
mclk_src_scaling[i].param) * (u64)fs;

There no reason the entire expression must use 64 bit multiplies, since the left side
above is know to fit in 32-bits.

The code could be more efficient if mclk_src_scaling had been sorted by scaling ratio
instead of register value. In fact, most of the math in this loop could be precomputed by the
compiler if one instead though of min and max fs range for a given scaler.