linux-kernel - [PATCH V3] cros_ec: Expose sysfile to force battery cut-off on shutdown.

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Message-Id: <20190305005300.129464-1-ravisadineni@chromium.org>
Date:   Mon,  4 Mar 2019 16:53:00 -0800
From:   RaviChandra Sadineni <ravisadineni@...omium.org>
To:     ravisadineni@...omium.org
Cc:     Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Guenter Roeck <groeck@...omium.org>,
        linux-kernel@...r.kernel.org, tbroch@...gle.com, dnojiri@...gle.com
Subject: [PATCH V3] cros_ec: Expose sysfile to force battery cut-off on shutdown.

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@...omium.org>
---

V3: Make battery-cutoff generic and expose 'at-shutdown' flag.
V2: Use kstrtobool() instead of kstrtou8() and add documentation.


.../ABI/testing/sysfs-class-chromeos          | 10 ++++
 drivers/platform/chrome/cros_ec_sysfs.c       | 48 +++++++++++++++++++
 2 files changed, 58 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..d5ab22c44977
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-chromeos
@@ -0,0 +1,10 @@
+What:           /sys/class/chromeos/cros_ec/battery-cuttoff
+Date:           February 2019
+Contact:        Ravi Chandra Sadineni <ravisadineni@...omium.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.
diff --git a/drivers/platform/chrome/cros_ec_sysfs.c b/drivers/platform/chrome/cros_ec_sysfs.c
index f34a50121064..6ef6b860c818 100644
--- a/drivers/platform/chrome/cros_ec_sysfs.c
+++ b/drivers/platform/chrome/cros_ec_sysfs.c
@@ -322,14 +322,62 @@ static ssize_t kb_wake_angle_store(struct device *dev,
 	return count;
 }
 
+/* Battery cut-off 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 =
+		container_of(dev, struct cros_ec_dev, class_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 {
+		kfree(msg);
+		return -EINVAL;
+	}
+
+	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);
+/*
+ * Currently EC does not expose a host command to read the status of
+ * battery cut-off configuration. Also there is no requirement to read
+ * the status of these flags 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