linux-kernel - [RFC PATCH v3 6/9] power: supply: Add batinfo functions for OCV to SOC with 0.1% accuracy

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Date:   Tue, 16 Nov 2021 14:27:40 +0200
From:   Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
To:     Matti Vaittinen <mazziesaccount@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc:     Sebastian Reichel <sre@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Lee Jones <lee.jones@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>, rostokus@...il.com,
        fan.chen@...iatek.com, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-power@...rohmeurope.com
Subject: [RFC PATCH v3 6/9] power: supply: Add batinfo functions for OCV to
 SOC with 0.1% accuracy

The battery info functions computing the state-of-charge (SOC) based
on open-circuit-voltage (OCV) are returning SOC using units of 1%.

Some capacity estimation computations require higher accuracy. Add
functions that return SOC using units of 0.1% to reduce rounding error.

Signed-off-by: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>

---

RFCv3 changes:
 - Kerneldoc fixes
---
 drivers/power/supply/power_supply_core.c | 65 ++++++++++++++++++++++++
 include/linux/power_supply.h             |  4 ++
 2 files changed, 69 insertions(+)

diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
index ebc961b5aa45..62ea113db3b4 100644
--- a/drivers/power/supply/power_supply_core.c
+++ b/drivers/power/supply/power_supply_core.c
@@ -1003,6 +1003,45 @@ int power_supply_ocv2cap_simple(struct power_supply_battery_ocv_table *table,
 }
 EXPORT_SYMBOL_GPL(power_supply_ocv2cap_simple);
 
+/**
+ * power_supply_ocv2dcap_simple() - find the battery capacity at 0.1% accuracy
+ * @table: Pointer to battery OCV lookup table
+ * @table_len: OCV table length
+ * @ocv: Current OCV value
+ *
+ * This helper function is used to look up battery capacity according to
+ * current OCV value from one OCV table, and the OCV table must be ordered
+ * descending. Return the SOC in the units of 0.1% for improved accuracy.
+ *
+ * Return: the battery capacity using the unit 0.1%.
+ */
+int power_supply_ocv2dcap_simple(struct power_supply_battery_ocv_table *table,
+				int table_len, int ocv)
+{
+	int i, cap, tmp;
+
+	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) * 10;
+		tmp /= table[i - 1].ocv - table[i].ocv;
+		cap = tmp + table[i].capacity * 10;
+	} else if (i == 0) {
+		cap = table[0].capacity * 10;
+	} else {
+		cap = table[table_len - 1].capacity * 10;
+	}
+
+	if (cap < 0)
+		cap = 0;
+
+	return cap;
+}
+EXPORT_SYMBOL_GPL(power_supply_ocv2dcap_simple);
+
 struct power_supply_battery_ocv_table *
 power_supply_find_ocv2cap_table(struct power_supply_battery_info *info,
 				int temp, int *table_len)
@@ -1054,6 +1093,32 @@ int power_supply_batinfo_dcap2ocv(struct power_supply_battery_info *info,
 }
 EXPORT_SYMBOL_GPL(power_supply_batinfo_dcap2ocv);
 
+/**
+ * power_supply_batinfo_ocv2dcap - compute SOC based on OCV and temperature
+ * @info:	pointer to battery information
+ * @ocv:	Open circuit voltage in uV
+ * @temp:	Temperature in Celsius
+ *
+ * Use OCV tables in battery info to compute the battery capacity based on
+ * provided open circuit voltage at given and temperature.
+ *
+ * Return: battery capacity correspondinggiven OCV and temperature at 0.1%.
+ *         -EINVAL if OCV table is not present.
+ */
+int power_supply_batinfo_ocv2dcap(struct power_supply_battery_info *info,
+				  int ocv, int temp)
+{
+	struct power_supply_battery_ocv_table *table;
+	int table_len;
+
+	table = power_supply_find_ocv2cap_table(info, temp, &table_len);
+	if (!table)
+		return -EINVAL;
+
+	return power_supply_ocv2dcap_simple(table, table_len, ocv);
+}
+EXPORT_SYMBOL_GPL(power_supply_batinfo_ocv2dcap);
+
 int power_supply_batinfo_ocv2cap(struct power_supply_battery_info *info,
 				 int ocv, int temp)
 {
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index c5118265b3ab..5e6575e97492 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -444,6 +444,10 @@ extern int power_supply_ocv2cap_simple(struct power_supply_battery_ocv_table *ta
 				       int table_len, int ocv);
 int power_supply_dcap2ocv_simple(struct power_supply_battery_ocv_table *table,
 				int table_len, int dcap);
+int power_supply_ocv2dcap_simple(struct power_supply_battery_ocv_table *table,
+				 int table_len, int ocv);
+int power_supply_batinfo_ocv2dcap(struct power_supply_battery_info *info,
+				  int ocv, int temp);
 
 extern struct power_supply_battery_ocv_table *
 power_supply_find_ocv2cap_table(struct power_supply_battery_info *info,
-- 
2.31.1


-- 
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =] 

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