[PATCH v2 0/2] fix an overflow error on sc27xx power supply

[PATCH v2 0/2] fix an overflow error on sc27xx power supply

[Chunyan Zhang]

From: Chunyan Zhang <chunyan.zhang@unisoc.com>

The patch 2/2 fixes an overflow error by changing to 64-bit divide operations.
In order to avoid compile error on 32-bit architectures, this patchset
also introduced a new 64-bit helper in patch 1/2.

Changes since v1: (https://lkml.org/lkml/2020/7/17/63)
- Added new help macro DIV_S64_ROUND_CLOSEST;
- Fixed an error reported by kernel test robot <lkp@intel.com>.

Chunyan Zhang (2):
  math64: New DIV_S64_ROUND_CLOSEST helper
  power: supply: sc27xx: prevent adc * 1000 from overflow

 drivers/power/supply/sc27xx_fuel_gauge.c |  9 +++++----
 include/linux/math64.h                   | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

-- 
2.20.1

[PATCH v2 1/2] math64: New DIV_S64_ROUND_CLOSEST helper

[Chunyan Zhang]

From: Chunyan Zhang <chunyan.zhang@unisoc.com>

Provide DIV_S64_ROUND_CLOSEST helper which uses div_s64 to perform
division rounded to the closest integer using signed 64bit
dividend and signed 32bit divisor.

Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
---
 include/linux/math64.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/math64.h b/include/linux/math64.h
index 11a267413e8e..cd0693989436 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -279,4 +279,23 @@ static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor)
 #define DIV64_U64_ROUND_CLOSEST(dividend, divisor)	\
 	({ u64 _tmp = (divisor); div64_u64((dividend) + _tmp / 2, _tmp); })
 
+/*
+ * DIV_S64_ROUND_CLOSEST - signed 64bit divide with 32bit divisor rounded to nearest integer
+ * @dividend: signed 64bit dividend
+ * @divisor: signed 32bit divisor
+ *
+ * Divide signed 64bit dividend by signed 32bit divisor
+ * and round to closest integer.
+ *
+ * Return: dividend / divisor rounded to nearest integer
+ */
+#define DIV_S64_ROUND_CLOSEST(dividend, divisor)(	\
+{							\
+	s64 __x = (dividend);				\
+	s32 __d = (divisor);				\
+	((__x > 0) == (__d > 0)) ?			\
+		div_s64((__x + (__d / 2)), __d) :	\
+		div_s64((__x - (__d / 2)), __d);	\
+}							\
+)
 #endif /* _LINUX_MATH64_H */
-- 
2.20.1

[PATCH v2 2/2] power: supply: sc27xx: prevent adc * 1000 from overflow

[Chunyan Zhang]

From: Chunyan Zhang <chunyan.zhang@unisoc.com>

The input parameter is int type, cause adc * 1000 could overflow.
Change to use s64 to avoid this issue.

Signed-off-by: Chen Yongzhi <yongzhi.chen@unisoc.com>
Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
---
 drivers/power/supply/sc27xx_fuel_gauge.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/power/supply/sc27xx_fuel_gauge.c b/drivers/power/supply/sc27xx_fuel_gauge.c
index be42e814ea34..9c627618c224 100644
--- a/drivers/power/supply/sc27xx_fuel_gauge.c
+++ b/drivers/power/supply/sc27xx_fuel_gauge.c
@@ -5,6 +5,7 @@
 #include <linux/iio/consumer.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/nvmem-consumer.h>
 #include <linux/of.h>
@@ -133,14 +134,14 @@ static const char * const sc27xx_charger_supply_name[] = {
 	"sc2723_charger",
 };
 
-static int sc27xx_fgu_adc_to_current(struct sc27xx_fgu_data *data, int adc)
+static int sc27xx_fgu_adc_to_current(struct sc27xx_fgu_data *data, s64 adc)
 {
-	return DIV_ROUND_CLOSEST(adc * 1000, data->cur_1000ma_adc);
+	return DIV_S64_ROUND_CLOSEST(adc * 1000, data->cur_1000ma_adc);
 }
 
-static int sc27xx_fgu_adc_to_voltage(struct sc27xx_fgu_data *data, int adc)
+static int sc27xx_fgu_adc_to_voltage(struct sc27xx_fgu_data *data, s64 adc)
 {
-	return DIV_ROUND_CLOSEST(adc * 1000, data->vol_1000mv_adc);
+	return DIV_S64_ROUND_CLOSEST(adc * 1000, data->vol_1000mv_adc);
 }
 
 static int sc27xx_fgu_voltage_to_adc(struct sc27xx_fgu_data *data, int vol)
-- 
2.20.1

Re: [PATCH v2 0/2] fix an overflow error on sc27xx power supply

[Sebastian Reichel]

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Hi,

On Fri, Jul 24, 2020 at 08:21:46PM +0800, Chunyan Zhang wrote:
> From: Chunyan Zhang <chunyan.zhang@unisoc.com>
> 
> The patch 2/2 fixes an overflow error by changing to 64-bit divide operations.
> In order to avoid compile error on 32-bit architectures, this patchset
> also introduced a new 64-bit helper in patch 1/2.
> 
> Changes since v1: (https://lkml.org/lkml/2020/7/17/63)
> - Added new help macro DIV_S64_ROUND_CLOSEST;
> - Fixed an error reported by kernel test robot <lkp@intel.com>.
> 
> Chunyan Zhang (2):
>   math64: New DIV_S64_ROUND_CLOSEST helper
>   power: supply: sc27xx: prevent adc * 1000 from overflow
> 
>  drivers/power/supply/sc27xx_fuel_gauge.c |  9 +++++----
>  include/linux/math64.h                   | 19 +++++++++++++++++++
>  2 files changed, 24 insertions(+), 4 deletions(-)

Thanks, queued.

-- Sebastian

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