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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Andrew Duggan <aduggan@synaptics.com>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 131/293] Input: synaptics-rmi4 - only read the
 F54 query registers which are used
Thread-Topic: [PATCH AUTOSEL for 4.9 131/293] Input: synaptics-rmi4 - only
 read the F54 query registers which are used
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Date:   Mon, 9 Apr 2018 00:24:35 +0000
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From: Andrew Duggan <aduggan@synaptics.com>

[ Upstream commit 9768935264c4f0e4afd788a185d8e8d89c28e41d ]

The F54 driver is currently only using the first 6 bytes of F54 so there is
no need to read all 27 bytes. Some Dell systems (Dell XP13 9333 and
similar) have an issue with the touchpad or I2C bus when reading reports
larger then 16 bytes. Reads larger then 16 bytes are reported in two HID
reports. Something about the back to back reports seems to cause the next
read to report incorrect data. This results in F30 failing to load and the
click button failing to work.

Previous issues with the I2C controller or touchpad were addressed in:
commit 5b65c2a02966 ("HID: rmi: check sanity of the incoming report")

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=3D195949
Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Reviewed-by: Nick Dyer <nick@shmanahar.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/input/rmi4/rmi_f54.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/input/rmi4/rmi_f54.c b/drivers/input/rmi4/rmi_f54.c
index 2e934aef3d2a..813bef40aab6 100644
--- a/drivers/input/rmi4/rmi_f54.c
+++ b/drivers/input/rmi4/rmi_f54.c
@@ -31,9 +31,6 @@
 #define F54_GET_REPORT          1
 #define F54_FORCE_CAL           2
=20
-/* Fixed sizes of reports */
-#define F54_QUERY_LEN			27
-
 /* F54 capabilities */
 #define F54_CAP_BASELINE	(1 << 2)
 #define F54_CAP_IMAGE8		(1 << 3)
@@ -95,7 +92,6 @@ struct rmi_f54_reports {
 struct f54_data {
 	struct rmi_function *fn;
=20
-	u8 qry[F54_QUERY_LEN];
 	u8 num_rx_electrodes;
 	u8 num_tx_electrodes;
 	u8 capabilities;
@@ -626,22 +622,23 @@ static int rmi_f54_detect(struct rmi_function *fn)
 {
 	int error;
 	struct f54_data *f54;
+	u8 buf[6];
=20
 	f54 =3D dev_get_drvdata(&fn->dev);
=20
 	error =3D rmi_read_block(fn->rmi_dev, fn->fd.query_base_addr,
-			       &f54->qry, sizeof(f54->qry));
+			       buf, sizeof(buf));
 	if (error) {
 		dev_err(&fn->dev, "%s: Failed to query F54 properties\n",
 			__func__);
 		return error;
 	}
=20
-	f54->num_rx_electrodes =3D f54->qry[0];
-	f54->num_tx_electrodes =3D f54->qry[1];
-	f54->capabilities =3D f54->qry[2];
-	f54->clock_rate =3D f54->qry[3] | (f54->qry[4] << 8);
-	f54->family =3D f54->qry[5];
+	f54->num_rx_electrodes =3D buf[0];
+	f54->num_tx_electrodes =3D buf[1];
+	f54->capabilities =3D buf[2];
+	f54->clock_rate =3D buf[3] | (buf[4] << 8);
+	f54->family =3D buf[5];
=20
 	rmi_dbg(RMI_DEBUG_FN, &fn->dev, "F54 num_rx_electrodes: %d\n",
 		f54->num_rx_electrodes);
--=20
2.15.1