HID: ft260: wake up device from power saving mode

The FT260 can enter a power saving mode after being idle for longer
than 5 seconds.

When being woken up from power saving mode by an I2C write request,
a possible NACK is not correctly reported by the controller. As a
workaround, the driver will issue an I2C status report two times in
ft260_xfer_status() after the chip has been idle for more than 5s.
Co-developed-by: Enrik Berkhan <Enrik.Berkhan@inka.de>
Signed-off-by: Enrik Berkhan <Enrik.Berkhan@inka.de>
Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-ft260.c

@@ -31,6 +31,8 @@ MODULE_PARM_DESC(debug, "Toggle FT260 debugging messages");
 #define FT260_REPORT_MAX_LENGTH (64)
 #define FT260_I2C_DATA_REPORT_ID(len) (FT260_I2C_REPORT_MIN + (len - 1) / 4)
 
+#define FT260_WAKEUP_NEEDED_AFTER_MS (4800) /* 5s minus 200ms margin */
+
 /*
  * The ft260 input report format defines 62 bytes for the data payload, but
  * when requested 62 bytes, the controller returns 60 and 2 in separate input
@@ -237,6 +239,7 @@ struct ft260_device {
 	struct completion wait;
 	struct mutex lock;
 	u8 write_buf[FT260_REPORT_MAX_LENGTH];
+	unsigned long need_wakeup_at;
 	u8 *read_buf;
 	u16 read_idx;
 	u16 read_len;
@@ -306,6 +309,20 @@ static int ft260_xfer_status(struct ft260_device *dev)
 	struct ft260_get_i2c_status_report report;
 	int ret;
 
+	if (time_is_before_jiffies(dev->need_wakeup_at)) {
+		ret = ft260_hid_feature_report_get(hdev, FT260_I2C_STATUS,
+						(u8 *)&report, sizeof(report));
+		if (unlikely(ret < 0)) {
+			hid_err(hdev, "failed to retrieve status: %d, no wakeup\n",
+				ret);
+		} else {
+			dev->need_wakeup_at = jiffies +
+				msecs_to_jiffies(FT260_WAKEUP_NEEDED_AFTER_MS);
+			ft260_dbg("bus_status %#02x, wakeup\n",
+				  report.bus_status);
+		}
+	}
+
 	ret = ft260_hid_feature_report_get(hdev, FT260_I2C_STATUS,
 					   (u8 *)&report, sizeof(report));
 	if (unlikely(ret < 0)) {