From c402714c643950ffe020804c98bb8e23e31ae050 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Jirman?= <megi@xff.cz>
Date: Wed, 23 Sep 2020 14:59:41 +0200
Subject: power: supply: axp20x_battery: Setup thermal regulation
 (experimental)

Values for NTC resistances were pulled out of thin air!

None of this is tested to actually work.

Signed-off-by: Ondrej Jirman <megi@xff.cz>
---
 drivers/power/supply/axp20x_battery.c | 53 +++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/drivers/power/supply/axp20x_battery.c b/drivers/power/supply/axp20x_battery.c
index f19ab493245b..1bac1a934614 100644
--- a/drivers/power/supply/axp20x_battery.c
+++ b/drivers/power/supply/axp20x_battery.c
@@ -1146,6 +1146,59 @@ static int axp20x_power_probe(struct platform_device *pdev)
 	 */
 	axp20x_get_constant_charge_current(axp20x_batt, &axp20x_batt->max_ccc);
 
+	if (of_machine_is_compatible("pine64,pinephone-1.2") > 0 ||
+		of_machine_is_compatible("pine64,pinephone-1.1") > 0 ||
+		of_machine_is_compatible("pine64,pinephone-1.0") > 0) {
+		// 3kOhm NTC inside PinePhone batery
+		// ---------------------------------
+		//
+		// Charging:
+		//  0 - 15 °C: Max 0.2C CC to 4.35V : 9750 Ohm - 4710 Ohm
+		// 15 - 50 °C: Max 0.5C CC to 4.35V : 4710 Ohm - 1080 Ohm
+		//
+		// Discharging:
+		// -10 °C : 16500 Ohm
+		//  55 °C : 896 Ohm
+		// enable TS pin input to ADC
+
+		dev_info(dev, "Configuring battery thermal regulation for Pinephone\n");
+
+		ret = regmap_update_bits(axp20x_batt->regmap, 0x82, BIT(0), BIT(0));
+		if (ret)
+			goto warn_bat;
+
+		// safety thresholds:
+
+		// voltage = reg_val * 12800 uV (range is 0 - 3.264V)
+		ret = regmap_write(axp20x_batt->regmap, 0x38,  9750 * 80 / 12800); // V_LTF-charge
+		if (ret)
+			goto warn_bat;
+
+		ret = regmap_write(axp20x_batt->regmap, 0x39,  1080 * 80 / 12800); // V_HTF-charge
+		if (ret)
+			goto warn_bat;
+
+		ret = regmap_write(axp20x_batt->regmap, 0x3c, 16500 * 80 / 12800); // V_LTF-work
+		if (ret)
+			goto warn_bat;
+
+		ret = regmap_write(axp20x_batt->regmap, 0x3d,   896 * 80 / 12800); // V_HTF-work
+		if (ret)
+			goto warn_bat;
+
+		// There is a hysteresis of 460.8 mV(refer to TS pin voltage) for UTP
+		// threshold, and there is a hysteresis of 57.6 mV for OTP threshold.
+
+		// use TS pin only when charging, make it affect the charger, I = 80uA
+		ret = regmap_update_bits(axp20x_batt->regmap, 0x84, 0x37, 0x31);
+		if (ret)
+			goto warn_bat;
+	}
+
+	return 0;
+
+warn_bat:
+	dev_err(dev, "Failed to configure battery thermal regulation\n");
 	return 0;
 }
 
-- 
2.35.3

