linux-kernel - Re: [RESEND] Lenovo Yoga 900 touchpad issues

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Date:	Fri, 18 Dec 2015 17:38:02 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Nish Aravamudan <nish.aravamudan@...il.com>
Cc:	Jiri Kosina <jikos@...nel.org>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Andrew Duggan <aduggan@...aptics.com>,
	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	Seth Forshee <seth.forshee@...onical.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-input@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND] Lenovo Yoga 900 touchpad issues

On Fri, Dec 18, 2015 at 04:42:09PM +0200, Mika Westerberg wrote:
> On another occasion the faulty input report was received immediatelly
> after we call i2c_hid_set_power().
> 
> With below hack patch suspend/resume works fine but it is far from being
> suitable for merging. Still, it would be nice if you could try it out
> and see if it helps in your case.

Actually it looks like we can handle this by just ignoring input reports
while we are resetting the device. Following seems to work as well.

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index 10bd8e6..eeaf33a 100644
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -352,13 +352,24 @@ static int i2c_hid_set_power(struct i2c_client *client, int power_state)
 static int i2c_hid_hwreset(struct i2c_client *client)
 {
 	struct i2c_hid *ihid = i2c_get_clientdata(client);
+	bool started;
 	int ret;
 
 	i2c_hid_dbg(ihid, "%s\n", __func__);
 
+	/*
+	 * Some touchpads seem to send input reports once their power is
+	 * turned back on after resume. This confuses our reset logic
+	 * below.
+	 *
+	 * Prevent handling any input reports while we are resetting the
+	 * device.
+	 */
+	started = test_and_clear_bit(I2C_HID_STARTED, &ihid->flags);
+
 	ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
 	if (ret)
-		return ret;
+		goto out;
 
 	i2c_hid_dbg(ihid, "resetting...\n");
 
@@ -366,10 +377,14 @@ 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);
-		return ret;
+		goto out;
 	}
 
-	return 0;
+out:
+	if (started)
+		set_bit(I2C_HID_STARTED, &ihid->flags);
+
+	return ret;
 }
 
 static void i2c_hid_get_input(struct i2c_hid *ihid)
--
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