From a4585ba2050f460f749bbaf2b67bd56c41e30283 Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@linaro.org>
Date: Wed, 17 Nov 2021 00:02:33 +0100
Subject: [PATCH] power: supply: core: Use library interpolation

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>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
 drivers/power/supply/power_supply_core.c | 57 ++++++++++++------------
 1 file changed, 29 insertions(+), 28 deletions(-)

diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
index fc12a4f407f4..2907b84ceea9 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;
+	/* The library function will deal with high == low */
+	if ((i == 0) || (i == (table_len - 1)))
+		high = i;
+	else
+		high = i - 1;
+	low = i;
 
-		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;
+	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;
 
-	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 (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;
-	}
+	/* The library function will deal with high == low */
+	if ((i == 0) || (i == (table_len - 1)))
+		high = i - 1;
+	else
+		high = i; /* i.e. i == 0 */
+	low = i;
 
-	return cap;
+	return fixp_linear_interpolate(table[low].ocv,
+				       table[low].capacity,
+				       table[high].ocv,
+				       table[high].capacity,
+				       ocv);
 }
 EXPORT_SYMBOL_GPL(power_supply_ocv2cap_simple);