[PATCH v2 0/3] LEGO MINDSTORMS EV3 Battery

[PATCH v2 0/3] LEGO MINDSTORMS EV3 Battery

[David Lechner]

This series adds support for the LEGO MINDSTORMS EV3 battery.

v2 changes:
* use devm_power_supply_register()

David Lechner (3):
  dt-bindings: power: supply: New bindings for LEGO MINDSTORMS EV3
    battery
  power: supply: New driver for LEGO MINDSTORMS EV3 battery
  ARM: dts: da850: Add node for LEGO MINDSTORMS EV3 Battery

 .../bindings/power/supply/lego_ev3_battery.txt     |  21 ++
 arch/arm/boot/dts/da850-lego-ev3.dts               |  28 +++
 drivers/power/supply/Kconfig                       |   6 +
 drivers/power/supply/Makefile                      |   1 +
 drivers/power/supply/lego_ev3_battery.c            | 228 +++++++++++++++++++++
 5 files changed, 284 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/power/supply/lego_ev3_battery.txt
 create mode 100644 drivers/power/supply/lego_ev3_battery.c

-- 
2.7.4

[PATCH v2 1/3] dt-bindings: power: supply: New bindings for LEGO MINDSTORMS EV3 battery

[David Lechner]

This add a new device tree binding for LEGO MINDSTORMS EV3 battery. The EV3
has some built-in capability for monitoring the attached battery.

Signed-off-by: David Lechner <david@lechnology.com>
Acked-by: Rob Herring <robh@kernel.org>
---
 .../bindings/power/supply/lego_ev3_battery.txt      | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/power/supply/lego_ev3_battery.txt

diff --git a/Documentation/devicetree/bindings/power/supply/lego_ev3_battery.txt b/Documentation/devicetree/bindings/power/supply/lego_ev3_battery.txt
new file mode 100644
index 0000000..5485633
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/supply/lego_ev3_battery.txt
@@ -0,0 +1,21 @@
+LEGO MINDSTORMS EV3 Battery
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+LEGO MINDSTORMS EV3 has some built-in capability for monitoring the battery.
+It uses 6 AA batteries or a special Li-ion rechargeable battery pack that is
+detected by a key switch in the battery compartment.
+
+Required properties:
+ - compatible: Must be "lego,ev3-battery"
+ - io-channels: phandles to analog inputs for reading voltage and current
+ - io-channel-names: Must be "voltage", "current"
+ - rechargeable-gpios: phandle to the rechargeable battery indication gpio
+
+Example:
+
+	battery {
+		compatible = "lego,ev3-battery";
+		io-channels = <&adc 4>, <&adc 3>;
+		io-channel-names = "voltage", "current";
+		rechargeable-gpios = <&gpio 136 GPIO_ACTIVE_LOW>;
+	};
-- 
2.7.4

[PATCH v2 2/3] power: supply: New driver for LEGO MINDSTORMS EV3 battery

[David Lechner]

This adds a new driver for the LEGO MINDSTORMS EV3 battery. The EV3 is
an embedded ARM device that can use 6 AA batteries or a special rechargeable
Li-ion battery pack. The rechargeable battery pack presses a special key
switch in the battery compartment to indicate that it is present.

The EV3 is only capable of monitoring battery voltage and current. The
charging circuit is built into the rechargeable battery pack and there is
no way to communicate with is, so we can't provide any information about
charging status.

When not using the rechargeable battery pack, it is most common to use
alkaline batteries to power the device, but it is also common for people to
use rechargeable NiMH batteries. Since there is not a way to automatically
differentiate between these, the technology property is made writable.

Signed-off-by: David Lechner <david@lechnology.com>
---
 drivers/power/supply/Kconfig            |   6 +
 drivers/power/supply/Makefile           |   1 +
 drivers/power/supply/lego_ev3_battery.c | 228 ++++++++++++++++++++++++++++++++
 3 files changed, 235 insertions(+)
 create mode 100644 drivers/power/supply/lego_ev3_battery.c

diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
index cc50e15..e00bf25 100644
--- a/drivers/power/supply/Kconfig
+++ b/drivers/power/supply/Kconfig
@@ -117,6 +117,12 @@ config BATTERY_DS2782
 	  Say Y here to enable support for the DS2782/DS2786 standalone battery
 	  gas-gauge.
 
+config BATTERY_LEGO_EV3
+	tristate "LEGO MINDSTORMS EV3 battery"
+	depends on OF && IIO && GPIOLIB
+	help
+	  Say Y here to enable support for the LEGO MINDSTORMS EV3 battery.
+
 config BATTERY_PMU
 	tristate "Apple PMU battery"
 	depends on PPC32 && ADB_PMU
diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
index 3789a2c..dfeadbc 100644
--- a/drivers/power/supply/Makefile
+++ b/drivers/power/supply/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_BATTERY_DS2781)	+= ds2781_battery.o
 obj-$(CONFIG_BATTERY_DS2782)	+= ds2782_battery.o
 obj-$(CONFIG_BATTERY_GAUGE_LTC2941)	+= ltc2941-battery-gauge.o
 obj-$(CONFIG_BATTERY_GOLDFISH)	+= goldfish_battery.o
+obj-$(CONFIG_BATTERY_LEGO_EV3)	+= lego_ev3_battery.o
 obj-$(CONFIG_BATTERY_PMU)	+= pmu_battery.o
 obj-$(CONFIG_BATTERY_OLPC)	+= olpc_battery.o
 obj-$(CONFIG_BATTERY_TOSA)	+= tosa_battery.o
diff --git a/drivers/power/supply/lego_ev3_battery.c b/drivers/power/supply/lego_ev3_battery.c
new file mode 100644
index 0000000..7b993d6
--- /dev/null
+++ b/drivers/power/supply/lego_ev3_battery.c
@@ -0,0 +1,228 @@
+/*
+ * Battery driver for LEGO MINDSTORMS EV3
+ *
+ * Copyright (C) 2017 David Lechner <david@lechnology.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+
+struct lego_ev3_battery {
+	struct iio_channel *iio_v;
+	struct iio_channel *iio_i;
+	struct gpio_desc *rechargeable_gpio;
+	struct power_supply *psy;
+	int technology;
+	int v_max;
+	int v_min;
+};
+
+static int lego_ev3_battery_get_property(struct power_supply *psy,
+					 enum power_supply_property psp,
+					 union power_supply_propval *val)
+{
+	struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);
+	int val2;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_TECHNOLOGY:
+		val->intval = batt->technology;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		/* battery voltage is iio channel * 2 + Vce of transistor */
+		iio_read_channel_processed(batt->iio_v, &val->intval);
+		val->intval *= 2000;
+		val->intval += 200000;
+		/* plus adjust for shunt resistor drop */
+		iio_read_channel_processed(batt->iio_i, &val2);
+		val2 *= 1000;
+		val2 /= 15;
+		val->intval += val2;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
+		val->intval = batt->v_max;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
+		val->intval = batt->v_min;
+		break;
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+		/* battery current is iio channel / 15 / 0.05 ohms */
+		iio_read_channel_processed(batt->iio_i, &val->intval);
+		val->intval *= 20000;
+		val->intval /= 15;
+		break;
+	case POWER_SUPPLY_PROP_SCOPE:
+		val->intval = POWER_SUPPLY_SCOPE_SYSTEM;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int lego_ev3_battery_set_property(struct power_supply *psy,
+					 enum power_supply_property psp,
+					 const union power_supply_propval *val)
+{
+	struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_TECHNOLOGY:
+		/*
+		 * Only allow changing technology from Unknown to NiMH. Li-ion
+		 * batteries are automatically detected and should not be
+		 * overridden. Rechargeable AA batteries, on the other hand,
+		 * cannot be automatically detected, and so must be manually
+		 * specified. This should only be set once during system init,
+		 * so there is no mechanism to go back to Unknown.
+		 */
+		if (batt->technology != POWER_SUPPLY_TECHNOLOGY_UNKNOWN)
+			return -EINVAL;
+		switch (val->intval) {
+		case POWER_SUPPLY_TECHNOLOGY_NiMH:
+			batt->technology = POWER_SUPPLY_TECHNOLOGY_NiMH;
+			batt->v_max = 7800000;
+			batt->v_min = 5400000;
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int lego_ev3_battery_property_is_writeable(struct power_supply *psy,
+						  enum power_supply_property psp)
+{
+	struct lego_ev3_battery *batt = power_supply_get_drvdata(psy);
+
+	return psp == POWER_SUPPLY_PROP_TECHNOLOGY &&
+		batt->technology == POWER_SUPPLY_TECHNOLOGY_UNKNOWN;
+}
+
+static enum power_supply_property lego_ev3_battery_props[] = {
+	POWER_SUPPLY_PROP_TECHNOLOGY,
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+	POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
+	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
+	POWER_SUPPLY_PROP_CURRENT_NOW,
+	POWER_SUPPLY_PROP_SCOPE,
+};
+
+static const struct power_supply_desc lego_ev3_battery_desc = {
+	.name			= "lego-ev3-battery",
+	.type			= POWER_SUPPLY_TYPE_BATTERY,
+	.properties		= lego_ev3_battery_props,
+	.num_properties		= ARRAY_SIZE(lego_ev3_battery_props),
+	.get_property		= lego_ev3_battery_get_property,
+	.set_property		= lego_ev3_battery_set_property,
+	.property_is_writeable	= lego_ev3_battery_property_is_writeable,
+};
+
+static int lego_ev3_battery_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct lego_ev3_battery *batt;
+	struct power_supply_config psy_cfg = {};
+	int err;
+
+	batt = devm_kzalloc(dev, sizeof(*batt), GFP_KERNEL);
+	if (!batt)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, batt);
+
+	batt->iio_v = devm_iio_channel_get(dev, "voltage");
+	err = PTR_ERR_OR_ZERO(batt->iio_v);
+	if (err) {
+		if (err != -EPROBE_DEFER)
+			dev_err(dev, "Failed to get voltage iio channel\n");
+		return err;
+	}
+
+	batt->iio_i = devm_iio_channel_get(dev, "current");
+	err = PTR_ERR_OR_ZERO(batt->iio_i);
+	if (err) {
+		if (err != -EPROBE_DEFER)
+			dev_err(dev, "Failed to get current iio channel\n");
+		return err;
+	}
+
+	batt->rechargeable_gpio = devm_gpiod_get(dev, "rechargeable", GPIOD_IN);
+	err = PTR_ERR_OR_ZERO(batt->rechargeable_gpio);
+	if (err) {
+		if (err != -EPROBE_DEFER)
+			dev_err(dev, "Failed to get rechargeable gpio\n");
+		return err;
+	}
+
+	/*
+	 * The rechargeable battery indication switch cannot be changed without
+	 * removing the battery, so we only need to read it once.
+	 */
+	if (gpiod_get_value(batt->rechargeable_gpio)) {
+		/* 2-cell Li-ion, 7.4V nominal */
+		batt->technology = POWER_SUPPLY_TECHNOLOGY_LION;
+		batt->v_max = 84000000;
+		batt->v_min = 60000000;
+	} else {
+		/* 6x AA Alkaline, 9V nominal */
+		batt->technology = POWER_SUPPLY_TECHNOLOGY_UNKNOWN;
+		batt->v_max = 90000000;
+		batt->v_min = 48000000;
+	}
+
+	psy_cfg.of_node = pdev->dev.of_node;
+	psy_cfg.drv_data = batt;
+
+	batt->psy = devm_power_supply_register(dev, &lego_ev3_battery_desc,
+					       &psy_cfg);
+	err = PTR_ERR_OR_ZERO(batt->psy);
+	if (err) {
+		dev_err(dev, "failed to register power supply\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id of_lego_ev3_battery_match[] = {
+	{ .compatible = "lego,ev3-battery", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, of_lego_ev3_battery_match);
+
+static struct platform_driver lego_ev3_battery_driver = {
+	.driver	= {
+		.name		= "lego-ev3-battery",
+		.of_match_table = of_lego_ev3_battery_match,
+	},
+	.probe	= lego_ev3_battery_probe,
+};
+module_platform_driver(lego_ev3_battery_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("David Lechner <david@lechnology.com>");
+MODULE_DESCRIPTION("LEGO MINDSTORMS EV3 Battery Driver");
-- 
2.7.4

[PATCH v2 3/3] ARM: dts: da850: Add node for LEGO MINDSTORMS EV3 Battery

[David Lechner]

This adds a new node to the LEGO MINDSTORMS EV3 device tree for the battery.

Signed-off-by: David Lechner <david@lechnology.com>
---
 arch/arm/boot/dts/da850-lego-ev3.dts | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/arm/boot/dts/da850-lego-ev3.dts b/arch/arm/boot/dts/da850-lego-ev3.dts
index c20580a..99cd561 100644
--- a/arch/arm/boot/dts/da850-lego-ev3.dts
+++ b/arch/arm/boot/dts/da850-lego-ev3.dts
@@ -172,6 +172,18 @@
 		gpio = <&gpio 111 GPIO_ACTIVE_HIGH>;
 		enable-active-high;
 	};
+
+	/*
+	 * The EV3 can use 6-AA batteries or a rechargeable Li-ion battery pack.
+	 */
+	battery {
+		pinctrl-names = "default";
+		pintctrl-0 = <&battery_pins>;
+		compatible = "lego,ev3-battery";
+		io-channels = <&adc 4>, <&adc 3>;
+		io-channel-names = "voltage", "current";
+		rechargeable-gpios = <&gpio 136 GPIO_ACTIVE_LOW>;
+	};
 };
 
 &pmx_core {
@@ -235,6 +247,15 @@
 			0x34 0x00000008 0x0000000f
 		>;
 	};
+
+	battery_pins: pinmux_battery_pins {
+		pinctrl-single,bits = <
+			/* GP0[6] */
+			0x04 0x00000080 0x000000f0
+			/* GP8[8] */
+			0x4c 0x00000080 0x000000f0
+		>;
+	};
 };
 
 &pinconf {
@@ -349,6 +370,13 @@
 
 &gpio {
 	status = "okay";
+
+	/* Don't pull down battery voltage adc io channel */
+	batt_volt_en {
+		gpio-hog;
+		gpios = <6 GPIO_ACTIVE_HIGH>;
+		output-low;
+	};
 };
 
 &usb_phy {
-- 
2.7.4

Re: [PATCH v2 1/3] dt-bindings: power: supply: New bindings for LEGO MINDSTORMS EV3 battery

[Sebastian Reichel]

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Hi,

On Tue, Apr 11, 2017 at 04:05:21PM -0500, David Lechner wrote:
> This add a new device tree binding for LEGO MINDSTORMS EV3 battery. The EV3
> has some built-in capability for monitoring the attached battery.
> 
> Signed-off-by: David Lechner <david@lechnology.com>
> Acked-by: Rob Herring <robh@kernel.org>

Thanks, queued.

-- Sebastian

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Re: [PATCH v2 2/3] power: supply: New driver for LEGO MINDSTORMS EV3 battery

[Sebastian Reichel]

[-- Attachment #1: Type: text/plain, Size: 1024 bytes --]

Hi,

On Tue, Apr 11, 2017 at 04:05:22PM -0500, David Lechner wrote:
> This adds a new driver for the LEGO MINDSTORMS EV3 battery. The EV3 is
> an embedded ARM device that can use 6 AA batteries or a special rechargeable
> Li-ion battery pack. The rechargeable battery pack presses a special key
> switch in the battery compartment to indicate that it is present.
> 
> The EV3 is only capable of monitoring battery voltage and current. The
> charging circuit is built into the rechargeable battery pack and there is
> no way to communicate with is, so we can't provide any information about
> charging status.
> 
> When not using the rechargeable battery pack, it is most common to use
> alkaline batteries to power the device, but it is also common for people to
> use rechargeable NiMH batteries. Since there is not a way to automatically
> differentiate between these, the technology property is made writable.
> 
> Signed-off-by: David Lechner <david@lechnology.com>

Thanks, queued.

-- Sebastian

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Re: [PATCH v2 3/3] ARM: dts: da850: Add node for LEGO MINDSTORMS EV3 Battery

[Sekhar Nori]

Hi David,

On Wednesday 12 April 2017 02:35 AM, David Lechner wrote:
> This adds a new node to the LEGO MINDSTORMS EV3 device tree for the battery.
> 
> Signed-off-by: David Lechner <david@lechnology.com>

I am done sending my pull requests for v4.12. So I added this to my
queue for v4.13

Thanks,
Sekhar