Add Raspberry Pi PoE+ HAT support

Signed-off-by: Serge Schneider <serge@raspberrypi.com>

drivers/power/supply/Kconfig

@@ -28,6 +28,12 @@ config POWER_SUPPLY_HWMON
 	  Say 'Y' here if you want power supplies to
 	  have hwmon sysfs interface too.
 
+config RPI_POE_POWER
+	tristate "Raspberry Pi PoE+ HAT power supply driver"
+	depends on RASPBERRYPI_FIRMWARE
+	help
+	  Say Y here to enable support for Raspberry Pi PoE+ (Power over Ethernet
+	  Plus) HAT current measurement.
 
 config PDA_POWER
 	tristate "Generic PDA/phone power driver"

drivers/power/supply/Makefile

@@ -9,6 +9,7 @@ obj-$(CONFIG_POWER_SUPPLY)	+= power_supply.o
 obj-$(CONFIG_POWER_SUPPLY_HWMON) += power_supply_hwmon.o
 obj-$(CONFIG_GENERIC_ADC_BATTERY)	+= generic-adc-battery.o
 
+obj-$(CONFIG_RPI_POE_POWER)	+= rpi_poe_power.o
 obj-$(CONFIG_PDA_POWER)		+= pda_power.o
 obj-$(CONFIG_APM_POWER)		+= apm_power.o
 obj-$(CONFIG_AXP20X_POWER)	+= axp20x_usb_power.o

drivers/power/supply/rpi_poe_power.c

@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * rpi-poe-power.c - Raspberry Pi PoE+ HAT power supply driver.
+ *
+ * Copyright (C) 2019 Raspberry Pi (Trading) Ltd.
+ * Based on axp20x_ac_power.c by Quentin Schulz <quentin.schulz@free-electrons.com>
+ *
+ * Author: Serge Schneider <serge@raspberrypi.org>
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+#define RPI_POE_ADC_REG			0x2
+#define RPI_POE_FLAG_REG		0x4
+
+#define RPI_POE_FLAG_AT			BIT(0)
+#define RPI_POE_FLAG_OC			BIT(1)
+
+#define RPI_POE_CURRENT_AF_MAX	(2500 * 1000)
+#define RPI_POE_CURRENT_AT_MAX	(5000 * 1000)
+
+#define DRVNAME "rpi-poe-power-supply"
+
+struct rpi_poe_power_supply_ctx {
+	struct power_supply *supply;
+	struct rpi_firmware *fw;
+};
+
+struct fw_tag_data_s {
+	u32 reg;
+	u32 val;
+	u32 ret;
+};
+
+static int write_reg(struct rpi_firmware *fw, u32 reg, u32 *val)
+{
+	struct fw_tag_data_s fw_tag_data = {
+		.reg = reg,
+		.val = *val
+	};
+	int ret;
+
+	ret = rpi_firmware_property(fw, RPI_FIRMWARE_SET_POE_HAT_VAL,
+				    &fw_tag_data, sizeof(fw_tag_data));
+	if (ret)
+		return ret;
+	else if (fw_tag_data.ret)
+		return -EIO;
+	return 0;
+}
+
+static int read_reg(struct rpi_firmware *fw, u32 reg, u32 *val)
+{
+	struct fw_tag_data_s fw_tag_data = {
+		.reg = reg,
+		.val = *val
+	};
+	int ret;
+
+	ret = rpi_firmware_property(fw, RPI_FIRMWARE_GET_POE_HAT_VAL,
+				    &fw_tag_data, sizeof(fw_tag_data));
+	if (ret)
+		return ret;
+	else if (fw_tag_data.ret)
+		return -EIO;
+
+	*val = fw_tag_data.val;
+	return 0;
+}
+
+static int rpi_poe_power_supply_get_property(struct power_supply *psy,
+					enum power_supply_property psp,
+					union power_supply_propval *r_val)
+{
+	struct rpi_poe_power_supply_ctx *ctx = power_supply_get_drvdata(psy);
+	int ret;
+	unsigned int val = 0;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_HEALTH:
+		ret = read_reg(ctx->fw, RPI_POE_FLAG_REG, &val);
+		if (ret)
+			return ret;
+
+		if (val & RPI_POE_FLAG_OC) {
+			r_val->intval = POWER_SUPPLY_HEALTH_UNSPEC_FAILURE;
+			val = RPI_POE_FLAG_OC;
+			ret = write_reg(ctx->fw, RPI_POE_FLAG_REG, &val);
+			if (ret)
+				return ret;
+			return 0;
+		}
+
+		r_val->intval = POWER_SUPPLY_HEALTH_GOOD;
+		return 0;
+
+	case POWER_SUPPLY_PROP_ONLINE:
+		ret = read_reg(ctx->fw, RPI_POE_ADC_REG, &val);
+		if (ret)
+			return ret;
+
+		r_val->intval = (val > 5);
+		return 0;
+
+	case POWER_SUPPLY_PROP_CURRENT_AVG:
+		val = 50;
+		ret = read_reg(ctx->fw, RPI_POE_ADC_REG, &val);
+		if (ret)
+			return ret;
+		val = (val * 3300)/9821;
+		r_val->intval = val * 1000;
+		return 0;
+
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+		ret = read_reg(ctx->fw, RPI_POE_ADC_REG, &val);
+		if (ret)
+			return ret;
+		val = (val * 3300)/9821;
+		r_val->intval = val * 1000;
+		return 0;
+
+	case POWER_SUPPLY_PROP_CURRENT_MAX:
+		ret = read_reg(ctx->fw, RPI_POE_FLAG_REG, &val);
+		if (ret)
+			return ret;
+
+		if (val & RPI_POE_FLAG_AT) {
+			r_val->intval = RPI_POE_CURRENT_AT_MAX;
+			return 0;
+		}
+		r_val->intval = RPI_POE_CURRENT_AF_MAX;
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}
+
+static enum power_supply_property rpi_poe_power_supply_properties[] = {
+	POWER_SUPPLY_PROP_HEALTH,
+	POWER_SUPPLY_PROP_ONLINE,
+	POWER_SUPPLY_PROP_CURRENT_AVG,
+	POWER_SUPPLY_PROP_CURRENT_NOW,
+	POWER_SUPPLY_PROP_CURRENT_MAX,
+};
+
+static const struct power_supply_desc rpi_poe_power_supply_desc = {
+	.name = "rpi-poe",
+	.type = POWER_SUPPLY_TYPE_MAINS,
+	.properties = rpi_poe_power_supply_properties,
+	.num_properties = ARRAY_SIZE(rpi_poe_power_supply_properties),
+	.get_property = rpi_poe_power_supply_get_property,
+};
+
+static int rpi_poe_power_supply_probe(struct platform_device *pdev)
+{
+	struct power_supply_config psy_cfg = {};
+	struct rpi_poe_power_supply_ctx *ctx;
+	struct device_node *fw_node;
+	u32 revision;
+
+	if (!of_device_is_available(pdev->dev.of_node))
+		return -ENODEV;
+
+	fw_node = of_parse_phandle(pdev->dev.of_node, "firmware", 0);
+	if (!fw_node) {
+		dev_err(&pdev->dev, "Missing firmware node\n");
+		return -ENOENT;
+	}
+
+	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->fw = rpi_firmware_get(fw_node);
+	if (!ctx->fw)
+		return -EPROBE_DEFER;
+	if (rpi_firmware_property(ctx->fw,
+			RPI_FIRMWARE_GET_FIRMWARE_REVISION,
+			&revision, sizeof(revision))) {
+		dev_err(&pdev->dev, "Failed to get firmware revision\n");
+		return -ENOENT;
+	}
+	if (revision < 0x60af72e8) {
+		dev_err(&pdev->dev, "Unsupported firmware\n");
+		return -ENOENT;
+	}
+	platform_set_drvdata(pdev, ctx);
+
+	psy_cfg.of_node = pdev->dev.of_node;
+	psy_cfg.drv_data = ctx;
+
+	ctx->supply = devm_power_supply_register(&pdev->dev,
+						   &rpi_poe_power_supply_desc,
+						   &psy_cfg);
+	if (IS_ERR(ctx->supply))
+		return PTR_ERR(ctx->supply);
+
+	return 0;
+}
+
+static const struct of_device_id of_rpi_poe_power_supply_match[] = {
+	{ .compatible = "raspberrypi,rpi-poe-power-supply", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, of_rpi_poe_power_supply_match);
+
+static struct platform_driver rpi_poe_power_supply_driver = {
+	.probe = rpi_poe_power_supply_probe,
+	.driver = {
+		.name = DRVNAME,
+		.of_match_table = of_rpi_poe_power_supply_match
+	},
+};
+
+module_platform_driver(rpi_poe_power_supply_driver);
+
+MODULE_AUTHOR("Serge Schneider <serge@raspberrypi.org>");
+MODULE_ALIAS("platform:" DRVNAME);
+MODULE_DESCRIPTION("Raspberry Pi PoE+ HAT power supply driver");
+MODULE_LICENSE("GPL");