From 43b7029f475e7497da1de1f4a1742241812bf266 Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede@redhat.com>
Date: Sun, 20 Oct 2019 23:47:18 +0200
Subject: [PATCH] HID: i2c-hid: Send power-on command after reset
Git-commit: 43b7029f475e7497da1de1f4a1742241812bf266
Patch-mainline: v5.4-rc7
References: git-fixes

Before commit 67b18dfb8cfc ("HID: i2c-hid: Remove runtime power
management"), any i2c-hid touchscreens would typically be runtime-suspended
between the driver loading and Xorg or a Wayland compositor opening it,
causing it to be resumed again. This means that before this change,
we would call i2c_hid_set_power(OFF), i2c_hid_set_power(ON) before the
graphical session would start listening to the touchscreen.

It turns out that at least some SIS touchscreens, such as the one found
on the Asus T100HA, need a power-on command after reset, otherwise they
will not send any events.

Fixes: 67b18dfb8cfc ("HID: i2c-hid: Remove runtime power management")
Cc: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/hid/i2c-hid/i2c-hid-core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index d9c55e30f986..04c088131e04 100644
--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -447,8 +447,12 @@ static int i2c_hid_hwreset(struct i2c_client *client)
 	if (ret) {
 		dev_err(&client->dev, "failed to reset device.\n");
 		i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
+		goto out_unlock;
 	}
 
+	/* At least some SIS devices need this after reset */
+	ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
+
 out_unlock:
 	mutex_unlock(&ihid->reset_lock);
 	return ret;
-- 
2.16.4