linux-kernel - [RFC PATCH v2 1/6] power: supply: add cap2ocv batinfo helper

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Message-ID: <f2866a9052bbeaa4b3795907f91974e1d18ef68e.1607085199.git.matti.vaittinen@fi.rohmeurope.com>
Date:   Fri, 4 Dec 2020 14:41:09 +0200
From:   Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
To:     matti.vaittinen@...rohmeurope.com, mazziesaccount@...il.com
Cc:     Sebastian Reichel <sebastian.reichel@...labora.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Dmitry Osipenko <digetx@...il.com>,
        Cong Pham <cpham2403@...il.com>, rostokus@...il.com,
        fan.chen@...iatek.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: [RFC PATCH v2 1/6] power: supply: add cap2ocv batinfo helper

The power-supply core supports concept of OCV (Open Circuit Voltage) =>
SOC (State Of Charge) conversion tables. Usually these tables are used
to estimate SOC based on OCV. Some systems use so called "Zero Adjust"
where at the near end-of-battery condition the SOC from coulomb counter
is used to retrieve the OCV - and OCV and VSYS difference is used to
re-estimate the battery capacity.

Add helper to do look-up the other-way around and also get the OCV
based on SOC

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

No changes from RFC v1 - (this should be changed to support at least
0.1% SOC accuracy - will rework for next version if this is continued)

 drivers/power/supply/power_supply_core.c | 51 ++++++++++++++++++++++++
 include/linux/power_supply.h             |  5 +++
 2 files changed, 56 insertions(+)

diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
index 38e3aa642131..67258799ae2e 100644
--- a/drivers/power/supply/power_supply_core.c
+++ b/drivers/power/supply/power_supply_core.c
@@ -787,6 +787,43 @@ int power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *t
 }
 EXPORT_SYMBOL_GPL(power_supply_temp2resist_simple);
 
+/**
+ * power_supply_cap2ocv_simple() - find the battery OCV by capacity
+ * @table: Pointer to battery OCV/CAP lookup table
+ * @table_len: OCV/CAP table length
+ * @cap: Current cap value
+ *
+ * This helper function is used to look up battery OCV according to
+ * current capacity value from one OCV table, and the OCV table must be ordered
+ * descending.
+ *
+ * Return: the battery OCV.
+ */
+int power_supply_cap2ocv_simple(struct power_supply_battery_ocv_table *table,
+				int table_len, int cap)
+{
+	int i, ocv, tmp;
+
+	for (i = 0; i < table_len; i++)
+		if (cap > table[i].capacity)
+			break;
+
+	if (i > 0 && i < table_len) {
+		tmp = (table[i - 1].ocv - table[i].ocv) *
+		      (cap - table[i].capacity);
+
+		tmp /= table[i - 1].capacity - table[i].capacity;
+		ocv = tmp + table[i].ocv;
+	} else if (i == 0) {
+		ocv = table[0].ocv;
+	} else {
+		ocv = table[table_len - 1].ocv;
+	}
+
+	return ocv;
+}
+EXPORT_SYMBOL_GPL(power_supply_cap2ocv_simple);
+
 /**
  * power_supply_ocv2cap_simple() - find the battery capacity
  * @table: Pointer to battery OCV lookup table
@@ -847,6 +884,20 @@ power_supply_find_ocv2cap_table(struct power_supply_battery_info *info,
 }
 EXPORT_SYMBOL_GPL(power_supply_find_ocv2cap_table);
 
+int power_supply_batinfo_cap2ocv(struct power_supply_battery_info *info,
+				 int cap, 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_cap2ocv_simple(table, table_len, cap);
+}
+EXPORT_SYMBOL_GPL(power_supply_batinfo_cap2ocv);
+
 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 81a55e974feb..bae98b628f92 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -403,11 +403,16 @@ extern void power_supply_put_battery_info(struct power_supply *psy,
 					  struct power_supply_battery_info *info);
 extern int power_supply_ocv2cap_simple(struct power_supply_battery_ocv_table *table,
 				       int table_len, int ocv);
+int power_supply_cap2ocv_simple(struct power_supply_battery_ocv_table *table,
+				int table_len, int cap);
+
 extern struct power_supply_battery_ocv_table *
 power_supply_find_ocv2cap_table(struct power_supply_battery_info *info,
 				int temp, int *table_len);
 extern int power_supply_batinfo_ocv2cap(struct power_supply_battery_info *info,
 					int ocv, int temp);
+int power_supply_batinfo_cap2ocv(struct power_supply_battery_info *info,
+				 int cap, int temp);
 extern int
 power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *table,
 				int table_len, int temp);
-- 
2.25.4


-- 
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 =]