[PATCH V4] cros_ec: Expose sysfile to force battery cutoff on shutdown.

[RaviChandra Sadineni <ravisadineni@chromium.org>]

From: RaviChandra Sadineni <ravisadineni@chromium.org>

On chromebooks, power_manager daemon normally shuts down(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 cutoff. This results in
battery deep discharging. This is a bad user experience as battery
has to trickle charge before booting when the AC 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 cutoff instead of hibernating when the system enters
S5 next time.

Signed-off-by: RaviChandra Sadineni <ravisadineni@chromium.org>
---
V4: Addressed comments from Enric.
V3: Make battery-cutoff generic and expose 'at-shutdown' flag.
V2: Use kstrtobool() instead of kstrtou8() and add documentation.

.../ABI/testing/sysfs-class-chromeos          | 16 +++++++
 drivers/platform/chrome/cros_ec_sysfs.c       | 47 +++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-chromeos b/Documentation/ABI/testing/sysfs-class-chromeos
index 5819699d66ec..0927704d1629 100644
--- a/Documentation/ABI/testing/sysfs-class-chromeos
+++ b/Documentation/ABI/testing/sysfs-class-chromeos
@@ -30,3 +30,19 @@ Date:		August 2015
 KernelVersion:	4.2
 Description:
 		Show the information about the EC software and hardware.
+
+What:           /sys/class/chromeos/<ec-device-name>/battery_cuttoff
+Date:           February 2019
+Contact:        Ravi Chandra Sadineni <ravisadineni@chromium.org>
+Description:
+                cros_ec battery cuttoff configuration. Only option
+                currently exposed is 'at-shutdown'.
+
+                'at-shutdown' sends a host command to EC requesting
+                battery cutoff on next shutdown. If AC is plugged
+                in before next shutdown, EC ignores the request and
+                resets the flag.
+
+                Currently EC does not expose a host command to read
+                the status of battery cutoff configuration. Thus this
+                flag is write-only.
diff --git a/drivers/platform/chrome/cros_ec_sysfs.c b/drivers/platform/chrome/cros_ec_sysfs.c
index fe0b7614ae1b..a35e1188f28f 100644
--- a/drivers/platform/chrome/cros_ec_sysfs.c
+++ b/drivers/platform/chrome/cros_ec_sysfs.c
@@ -308,14 +308,61 @@ static ssize_t kb_wake_angle_store(struct device *dev,
 	return count;
 }
 
+/* Battery cutoff control */
+static ssize_t battery_cutoff_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 = to_cros_ec_dev(dev);
+	char *p;
+	int len;
+
+	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;
+	msg->outsize = sizeof(*param);
+	msg->insize = 0;
+
+	p = memchr(buf, '\n', count);
+	len = p ? p - buf : count;
+
+	if (len == 11 && !strncmp(buf, "at-shutdown", len)) {
+		param->flags = EC_BATTERY_CUTOFF_FLAG_AT_SHUTDOWN;
+	} else {
+		count = -EINVAL;
+		goto exit;
+	}
+
+	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
+	if (ret < 0)
+		count = ret;
+exit:
+	kfree(msg);
+	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);
+/*
+ * Currently EC does not expose a host command to read the status of
+ * battery cutoff configuration. Also there is no requirement to read
+ * the flag from userland. So marking this attribute as write-only.
+ */
+static DEVICE_ATTR_WO(battery_cutoff);
 
 static struct attribute *__ec_attrs[] = {
+	&dev_attr_battery_cutoff.attr,
 	&dev_attr_kb_wake_angle.attr,
 	&dev_attr_reboot.attr,
 	&dev_attr_version.attr,
-- 
2.20.1