[PATCH V2] cros_ec: Expose sysfile to force battery cut-off on shutdown.

[RaviChandra Sadineni <ravisadineni@chromium.org>]

On chromebooks, power_manager daemon normally shutsdown(S5) the device
when the battery charge falls below 4% threshold. Chromeos EC then
normally spends an hour in S5 before hibernating. If the battery charge
falls below critical threshold in the mean time, EC does a battery cutoff
instead of hibernating. On some chromebooks, S5 is optimal enough
resulting in EC hibernating without battery cut-off. This results in
battery deep-discharging. This is a bad user experience as battery
has to trickle charge before booting when the A.C is plugged in the next
time.

This patch exposes a sysfs file for an userland daemon to suggest EC if it
has to do a battery cut-off instead of hibernating when the system enters
S5 next time.

Signed-off-by: RaviChandra Sadineni <ravisadineni@chromium.org>
---
V2: Use kstrtobool() instead of kstrtou8() and add documentation.

 .../ABI/testing/sysfs-class-chromeos          |  8 ++++
 drivers/platform/chrome/cros_ec_sysfs.c       | 37 +++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-class-chromeos

diff --git a/Documentation/ABI/testing/sysfs-class-chromeos b/Documentation/ABI/testing/sysfs-class-chromeos
new file mode 100644
index 000000000000..44d3cee6e7ae
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-chromeos
@@ -0,0 +1,8 @@
+What:           /sys/class/chromeos/cros_ec/cutoff_at_shutdown
+Date:           February 2019
+Contact:        Ravi Chandra Sadineni <ravisadineni@chromium.org>
+Description:
+                On writing '[Yy1]' to cutoff_at_shutdown property,
+                kernel sends a host command to EC requesting battery
+                cutoff on next shutdown. If AC is plugged in before
+                next shutdown, EC resets this flag.
diff --git a/drivers/platform/chrome/cros_ec_sysfs.c b/drivers/platform/chrome/cros_ec_sysfs.c
index f34a50121064..f5168ce8bfc7 100644
--- a/drivers/platform/chrome/cros_ec_sysfs.c
+++ b/drivers/platform/chrome/cros_ec_sysfs.c
@@ -322,14 +322,51 @@ static ssize_t kb_wake_angle_store(struct device *dev,
 	return count;
 }
 
+/* Battery cut-off control */
+static ssize_t cutoff_at_shutdown_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	struct ec_params_battery_cutoff *param;
+	struct cros_ec_command *msg;
+	int ret;
+	struct cros_ec_dev *ec = container_of(
+			dev, struct cros_ec_dev, class_dev);
+	bool cutoff_battery;
+
+	if (kstrtobool(buf, &cutoff_battery))
+		return -EINVAL;
+
+	if (!cutoff_battery)
+		return count;
+
+	msg = kmalloc(sizeof(*msg) + EC_HOST_PARAM_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	param = (struct ec_params_battery_cutoff *)msg->data;
+	msg->command = EC_CMD_BATTERY_CUT_OFF + ec->cmd_offset;
+	msg->version = 1;
+	param->flags = EC_BATTERY_CUTOFF_FLAG_AT_SHUTDOWN;
+	msg->outsize = sizeof(*param);
+	msg->insize = 0;
+	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
+	kfree(msg);
+	if (ret < 0)
+		return ret;
+	return count;
+}
+
 /* Module initialization */
 
 static DEVICE_ATTR_RW(reboot);
 static DEVICE_ATTR_RO(version);
 static DEVICE_ATTR_RO(flashinfo);
 static DEVICE_ATTR_RW(kb_wake_angle);
+static DEVICE_ATTR_WO(cutoff_at_shutdown);
 
 static struct attribute *__ec_attrs[] = {
+	&dev_attr_cutoff_battery_at_shutdown.attr,
 	&dev_attr_kb_wake_angle.attr,
 	&dev_attr_reboot.attr,
 	&dev_attr_version.attr,
-- 
2.20.1