Patch "HID: i2c-hid: Add sleep between POWER ON and RESET" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

HID: i2c-hid: Add sleep between POWER ON and RESET

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
hid-i2c-hid-add-sleep-between-power-on-and-reset.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Brendan McGrath <[email protected]>
Date: Sat, 7 Jan 2017 08:01:38 +1100
Subject: HID: i2c-hid: Add sleep between POWER ON and RESET

From: Brendan McGrath <[email protected]>

[ Upstream commit a89af4abdf9b353cdd6f61afc0eaaac403304873 ]

Support for the Asus Touchpad was recently added. It turns out this device can fail initialisation (and become unusable) when the RESET command is sent too soon after the POWER ON command.

Unfortunately the i2c-hid specification does not specify the need for a delay between these two commands. But it was discovered the Windows driver has a 1ms delay.

As a result, this patch modifies the i2c-hid module to add a sleep inbetween the POWER ON and RESET commands which lasts between 1ms and 5ms.

See https://github.com/vlasenko/hid-asus-dkms/issues/24 for further details.

---
 drivers/hid/i2c-hid/i2c-hid.c |    9 +++++++++
 1 file changed, 9 insertions(+)

@@ -427,6 +427,15 @@ static int i2c_hid_hwreset(struct i2c_cl
 	if (ret)
 		goto out_unlock;
 
+	/*
+	 * The HID over I2C specification states that if a DEVICE needs time
+	 * after the PWR_ON request, it should utilise CLOCK stretching.
+	 * However, it has been observered that the Windows driver provides a
+	 * 1ms sleep between the PWR_ON and RESET requests and that some devices
+	 * rely on this.
+	 */
+	usleep_range(1000, 5000);
+
 	i2c_hid_dbg(ihid, "resetting...\n");
 
 	ret = i2c_hid_command(client, &hid_reset_cmd, NULL, 0);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/hid-i2c-hid-add-sleep-between-power-on-and-reset.patch