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authorBrendan McGrath <redmcg@redmandi.dyndns.org>2017-01-07 08:01:38 +1100
committerJiri Kosina <jkosina@suse.cz>2017-01-11 21:55:35 +0100
commita89af4abdf9b353cdd6f61afc0eaaac403304873 (patch)
tree340ac23fe4ee8d576a9be12146b94234f31cc2a7
parent1ebb71143758f45dc0fa76e2f48429e13b16d110 (diff)
HID: i2c-hid: Add sleep between POWER ON and RESET
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. Signed-off-by: Brendan McGrath <redmcg@redmandi.dyndns.org> Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
-rw-r--r--drivers/hid/i2c-hid/i2c-hid.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index 78fb32a7b103..ea3c3546cef7 100644
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -426,6 +426,15 @@ static int i2c_hid_hwreset(struct i2c_client *client)
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);