[PATCH v2] power: supply: core: Use library interpolation

Linus Walleij
2021-11-16T03:57:31Z

The power supply core appears to contain two open coded
linear interpolations. Use the kernel fixpoint arithmetic
interpolation library function instead.

Cc: Chunyan Zhang <chunyan.zhang@unisoc.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v1->v2:
- Break the table loop at table_len - 1 so we don't index
past the end of the table. (Thanks Baolin!)

Chunyan: The sc27xx fuel gauge seems to be the only driver
using this, so it'd be great if you could test this to make
sure it works as intended.
---
drivers/power/supply/power_supply_core.c | 59 ++++++++++++------------
1 file changed, 30 insertions(+), 29 deletions(-)

diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
index fc12a4f407f4..2983466a4914 100644
--- a/drivers/power/supply/power_supply_core.c
+++ b/drivers/power/supply/power_supply_core.c
@@ -21,6 +21,7 @@
#include <linux/power_supply.h>
#include <linux/property.h>
#include <linux/thermal.h>
+#include <linux/fixp-arith.h>
#include "power_supply.h"

/* exported for the APM Power driver, APM emulation */
@@ -783,26 +784,25 @@ EXPORT_SYMBOL_GPL(power_supply_put_battery_info);
int power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *table,
int table_len, int temp)
{
- int i, resist;
+ int i, high, low;

- for (i = 0; i < table_len; i++)
+ /* Break loop at table_len - 1 because that is the highest index */
+ for (i = 0; i < table_len - 1; i++)
if (temp > table[i].temp)
break;

- if (i > 0 && i < table_len) {
- int tmp;
-
- tmp = (table[i - 1].resistance - table[i].resistance) *
- (temp - table[i].temp);
- tmp /= table[i - 1].temp - table[i].temp;
- resist = tmp + table[i].resistance;
- } else if (i == 0) {
- resist = table[0].resistance;
- } else {
- resist = table[table_len - 1].resistance;
- }
-
- return resist;
+ /* The library function will deal with high == low */
+ if (i > 0)
+ high = i - 1;
+ else
+ high = i; /* i.e. i == 0 */
+ low = i;
+
+ return fixp_linear_interpolate(table[low].temp,
+ table[low].resistance,
+ table[high].temp,
+ table[high].resistance,
+ temp);
}
EXPORT_SYMBOL_GPL(power_supply_temp2resist_simple);

@@ -821,24 +821,25 @@ EXPORT_SYMBOL_GPL(power_supply_temp2resist_simple);
int power_supply_ocv2cap_simple(struct power_supply_battery_ocv_table *table,
int table_len, int ocv)
{
- int i, cap, tmp;
+ int i, high, low;

+ /* Break loop at table_len - 1 because that is the highest index */
for (i = 0; i < table_len; i++)
if (ocv > table[i].ocv)
break;

- if (i > 0 && i < table_len) {
- tmp = (table[i - 1].capacity - table[i].capacity) *
- (ocv - table[i].ocv);
- tmp /= table[i - 1].ocv - table[i].ocv;
- cap = tmp + table[i].capacity;
- } else if (i == 0) {
- cap = table[0].capacity;
- } else {
- cap = table[table_len - 1].capacity;
- }
-
- return cap;
+ /* The library function will deal with high == low */
+ if (i > 0)
+ high = i - 1;
+ else
+ high = i; /* i.e. i == 0 */
+ low = i;
+
+ return fixp_linear_interpolate(table[low].ocv,
+ table[low].capacity,
+ table[high].ocv,
+ table[high].capacity,
+ ocv);
}
EXPORT_SYMBOL_GPL(power_supply_ocv2cap_simple);

--
2.31.1