[PATCH v3 2/2] platform/chrome: wilco_ec: Add USB PowerShare Policy control

[Nick Crews]

USB PowerShare is a policy which affects charging via the special
USB PowerShare port (marked with a small lightning bolt or battery icon)
when in low power states:
- In S0, the port will always provide power.
- In S0ix, if power_share is enabled, then power will be supplied to
  the port when on AC or if battery is > 50%. Else no power is supplied.
- In S5, if power_share is enabled, then power will be supplied to
  the port when on AC. Else no power is supplied.

v3 changes:
- Drop a silly blank line
- Use val > 1 instead of val != 0 && val != 1
v2 changes:
- Move documentation to Documentation/ABI/testing/sysfs-platform-wilco-ec
- Zero out reserved bytes in requests.

Signed-off-by: Nick Crews <ncrews@xxxxxxxxxxxx>
---
 .../ABI/testing/sysfs-platform-wilco-ec       | 16 ++++
 drivers/platform/chrome/wilco_ec/sysfs.c      | 92 +++++++++++++++++++
 2 files changed, 108 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-platform-wilco-ec b/Documentation/ABI/testing/sysfs-platform-wilco-ec
index e074c203cd32..0c07d5e0b737 100644
--- a/Documentation/ABI/testing/sysfs-platform-wilco-ec
+++ b/Documentation/ABI/testing/sysfs-platform-wilco-ec
@@ -9,3 +9,19 @@ Description:
 		Input should be parseable by kstrtou8() to 0 or 1.
 		Output will be either "0\n" or "1\n".
 
+What:		/sys/bus/platform/devices/GOOG000C\:00/usb_power_share
+Date:		April 2019
+KernelVersion:	5.2
+Description:
+		Control the USB PowerShare Policy. USB PowerShare is a policy
+		which affects charging via the special USB PowerShare port
+		(marked with a small lightning bolt or battery icon) when in
+		low power states:
+		- In S0, the port will always provide power.
+		- In S0ix, if power_share is enabled, then power will be
+		  supplied to the port when on AC or if battery is > 50%.
+		  Else no power is supplied.
+		- In S5, if power_share is enabled, then power will be supplied
+		  to the port when on AC. Else no power is supplied.
+
+		Input should be either "0" or "1".
diff --git a/drivers/platform/chrome/wilco_ec/sysfs.c b/drivers/platform/chrome/wilco_ec/sysfs.c
index 959b5da2eb16..14e1eee95d42 100644
--- a/drivers/platform/chrome/wilco_ec/sysfs.c
+++ b/drivers/platform/chrome/wilco_ec/sysfs.c
@@ -23,6 +23,26 @@ struct boot_on_ac_request {
 	u8 reserved7;
 } __packed;
 
+#define CMD_USB_POWER_SHARE 0x39
+
+enum usb_power_share_op {
+	POWER_SHARE_GET = 0,
+	POWER_SHARE_SET = 1,
+};
+
+struct usb_power_share_request {
+	u8 cmd;		/* Always CMD_USB_POWER_SHARE */
+	u8 reserved;
+	u8 op;		/* One of enum usb_power_share_op */
+	u8 val;		/* When setting, either 0 or 1 */
+} __packed;
+
+struct usb_power_share_response {
+	u8 reserved;
+	u8 status;	/* Set by EC to 0 on success, other value on failure */
+	u8 val;		/* When getting, set by EC to either 0 or 1 */
+} __packed;
+
 static ssize_t boot_on_ac_store(struct device *dev,
 				struct device_attribute *attr,
 				const char *buf, size_t count)
@@ -57,8 +77,80 @@ static ssize_t boot_on_ac_store(struct device *dev,
 
 static DEVICE_ATTR_WO(boot_on_ac);
 
+static int send_usb_power_share(struct wilco_ec_device *ec,
+				struct usb_power_share_request *rq,
+				struct usb_power_share_response *rs)
+{
+	struct wilco_ec_message msg;
+	int ret;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.type = WILCO_EC_MSG_LEGACY;
+	msg.request_data = rq;
+	msg.request_size = sizeof(*rq);
+	msg.response_data = rs;
+	msg.response_size = sizeof(*rs);
+	ret = wilco_ec_mailbox(ec, &msg);
+	if (ret < 0)
+		return ret;
+	if (rs->status)
+		return -EIO;
+
+	return 0;
+}
+
+static ssize_t usb_power_share_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct wilco_ec_device *ec = dev_get_drvdata(dev);
+	struct usb_power_share_request rq;
+	struct usb_power_share_response rs;
+	int ret;
+
+	memset(&rq, 0, sizeof(rq));
+	rq.cmd = CMD_USB_POWER_SHARE;
+	rq.op = POWER_SHARE_GET;
+
+	ret = send_usb_power_share(ec, &rq, &rs);
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "%d\n", rs.val);
+}
+
+static ssize_t usb_power_share_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct wilco_ec_device *ec = dev_get_drvdata(dev);
+	struct usb_power_share_request rq;
+	struct usb_power_share_response rs;
+	int ret;
+	u8 val;
+
+	ret = kstrtou8(buf, 10, &val);
+	if (ret < 0)
+		return ret;
+	if (val > 1)
+		return -EINVAL;
+
+	memset(&rq, 0, sizeof(rq));
+	rq.cmd = CMD_USB_POWER_SHARE;
+	rq.op = POWER_SHARE_SET;
+	rq.val = val;
+
+	ret = send_usb_power_share(ec, &rq, &rs);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(usb_power_share);
+
 static struct attribute *wilco_dev_attrs[] = {
 	&dev_attr_boot_on_ac.attr,
+	&dev_attr_usb_power_share.attr,
 	NULL,
 };
 
-- 
2.20.1