[PATCH v2 4/6] platform/x86: huawei-wmi: Add battery charging thresholds

[Ayman Bagabas <ayman.bagabas@gmail.com>]

Controll battery charge thresholds through the battery API and driver's
attributes.

Setting battery charging thresholds can introduce a race condition with
MACH-WX9 where two or more threads are trying to read/write values
from/to EC memory.

Signed-off-by: Ayman Bagabas <ayman.bagabas@gmail.com>
---
 drivers/platform/x86/huawei-wmi.c | 212 ++++++++++++++++++++++++++++++
 1 file changed, 212 insertions(+)

diff --git a/drivers/platform/x86/huawei-wmi.c b/drivers/platform/x86/huawei-wmi.c
index 904ef38944b6..231b5cce00db 100644
--- a/drivers/platform/x86/huawei-wmi.c
+++ b/drivers/platform/x86/huawei-wmi.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/delay.h>
 #include <linux/dmi.h>
 #include <linux/input.h>
 #include <linux/input/sparse-keymap.h>
@@ -13,7 +14,10 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <linux/sysfs.h>
 #include <linux/wmi.h>
+#include <acpi/battery.h>
 
 /*
  * Huawei WMI GUIDs
@@ -54,11 +58,14 @@ struct huawei_wmi_debug {
 };
 
 struct huawei_wmi {
+	bool battery_available;
+
 	struct huawei_wmi_debug debug;
 	struct input_dev *idev[2];
 	struct led_classdev cdev;
 	struct platform_device *pdev;
 
+	struct mutex battery_lock;
 	struct mutex wmi_lock;
 };
 
@@ -306,6 +313,208 @@ static void huawei_wmi_leds_setup(struct device *dev)
 	devm_led_classdev_register(dev, &huawei->cdev);
 }
 
+/* Battery protection */
+
+static int huawei_wmi_battery_get(int *start, int *end)
+{
+	u8 ret[0x100];
+	int err, i;
+
+	err = huawei_wmi_cmd(BATTERY_THRESH_GET, ret, 0x100);
+	if (err)
+		return err;
+
+	/* Find the last two non-zero values. Return status is ignored. */
+	i = 0x100;
+	do {
+		if (start)
+			*start = ret[i-1];
+		if (end)
+			*end = ret[i];
+	} while (i > 2 && !ret[i--]);
+
+	return 0;
+}
+
+static int huawei_wmi_battery_set(int start, int end)
+{
+	union hwmi_arg arg;
+	int err;
+
+	if (start < 0 || end > 100)
+		return -EINVAL;
+
+	arg.cmd = BATTERY_THRESH_SET;
+	arg.args[2] = start;
+	arg.args[3] = end;
+
+	/* This is an edge case were some models turn battery protection
+	 * off without changing their thresholds values. We clear the
+	 * values before turning off protection. Sometimes we need a sleep delay to
+	 * make sure these values make their way to EC memory.
+	 */
+	if (quirks && quirks->battery_reset && start == 0 && end == 100) {
+		err = huawei_wmi_battery_set(0, 0);
+		if (err)
+			return err;
+
+		msleep(1000);
+	}
+
+	err = huawei_wmi_cmd(arg.cmd, NULL, NULL);
+
+	return err;
+}
+
+static ssize_t charge_control_start_threshold_show(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	int err, start;
+
+	err = huawei_wmi_battery_get(&start, NULL);
+	if (err)
+		return err;
+
+	return sprintf(buf, "%d\n", start);
+}
+
+static ssize_t charge_control_end_threshold_show(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	int err, end;
+
+	err = huawei_wmi_battery_get(NULL, &end);
+	if (err)
+		return err;
+
+	return sprintf(buf, "%d\n", end);
+}
+
+static ssize_t charge_control_thresholds_show(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	int err, start, end;
+
+	err = huawei_wmi_battery_get(&start, &end);
+	if (err)
+		return err;
+
+	return sprintf(buf, "%d %d\n", start, end);
+}
+
+static ssize_t charge_control_start_threshold_store(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t size)
+{
+	int err, start, end;
+
+	err = huawei_wmi_battery_get(NULL, &end);
+	if (err)
+		return err;
+
+	if (sscanf(buf, "%d", &start) != 1)
+		return -EINVAL;
+
+	err = huawei_wmi_battery_set(start, end);
+	if (err)
+		return err;
+
+	return size;
+}
+
+static ssize_t charge_control_end_threshold_store(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t size)
+{
+	int err, start, end;
+
+	err = huawei_wmi_battery_get(&start, NULL);
+	if (err)
+		return err;
+
+	if (sscanf(buf, "%d", &end) != 1)
+		return -EINVAL;
+
+	err = huawei_wmi_battery_set(start, end);
+	if (err)
+		return err;
+
+	return size;
+}
+
+static ssize_t charge_control_thresholds_store(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf, size_t size)
+{
+	int err, start, end;
+
+	if (sscanf(buf, "%d %d", &start, &end) != 2)
+		return -EINVAL;
+
+	err = huawei_wmi_battery_set(start, end);
+	if (err)
+		return err;
+
+	return size;
+}
+
+static DEVICE_ATTR_RW(charge_control_start_threshold);
+static DEVICE_ATTR_RW(charge_control_end_threshold);
+static DEVICE_ATTR_RW(charge_control_thresholds);
+
+static int huawei_wmi_battery_add(struct power_supply *battery)
+{
+	/* Huawei laptops come with one battery only */
+	if (strcmp(battery->desc->name, "BAT") != 1)
+		return -ENODEV;
+
+	device_create_file(&battery->dev, &dev_attr_charge_control_start_threshold);
+	device_create_file(&battery->dev, &dev_attr_charge_control_end_threshold);
+
+	return 0;
+}
+
+static int huawei_wmi_battery_remove(struct power_supply *battery)
+{
+	device_remove_file(&battery->dev, &dev_attr_charge_control_start_threshold);
+	device_remove_file(&battery->dev, &dev_attr_charge_control_end_threshold);
+
+	return 0;
+}
+
+static struct acpi_battery_hook huawei_wmi_battery_hook = {
+	.add_battery = huawei_wmi_battery_add,
+	.remove_battery = huawei_wmi_battery_remove,
+	.name = "Huawei Battery Extension"
+};
+
+static void huawei_wmi_battery_setup(struct device *dev)
+{
+	struct huawei_wmi *huawei = dev_get_drvdata(dev);
+
+	huawei->battery_available = true;
+	if (huawei_wmi_battery_get(NULL, NULL)) {
+		huawei->battery_available = false;
+		return;
+	}
+
+	battery_hook_register(&huawei_wmi_battery_hook);
+	device_create_file(dev, &dev_attr_charge_control_thresholds);
+}
+
+static void huawei_wmi_battery_exit(struct device *dev)
+{
+	struct huawei_wmi *huawei = dev_get_drvdata(dev);
+
+	if (huawei->battery_available) {
+		battery_hook_unregister(&huawei_wmi_battery_hook);
+		device_remove_file(dev, &dev_attr_charge_control_thresholds);
+	}
+}
+
 /* Input */
 
 static void huawei_wmi_process_key(struct input_dev *idev, int code)
@@ -426,8 +635,10 @@ static int huawei_wmi_probe(struct platform_device *pdev)
 
 	if (wmi_has_guid(HWMI_METHOD_GUID)) {
 		mutex_init(&huawei_wmi->wmi_lock);
+		mutex_init(&huawei_wmi->battery_lock);
 
 		huawei_wmi_leds_setup(&pdev->dev);
+		huawei_wmi_battery_setup(&pdev->dev);
 	}
 
 	return 0;
@@ -445,6 +656,7 @@ static int huawei_wmi_remove(struct platform_device *pdev)
 	}
 
 	if (wmi_has_guid(HWMI_METHOD_GUID)) {
+		huawei_wmi_battery_exit(&pdev->dev);
 	}
 
 	return 0;
-- 
2.21.0