[PATCH] Input: goodix - sync the irq controller while starting firmware

[Luca Leonardo Scorcia <l.scorcia@gmail.com>]

On the Lenovo Tab E7 TB-7104F which has a Goodix GT-912F touch screen,
the touch screen fails to come online after loading firmware, producing
the error "Error reading 1 bytes from 0x8041: -6".

Comparing the upstream code with the Android stock sources a call to
goodix_int_sync is required between the upload of the firmware and the
watchdog restart. With this change the touchscreen is correctly detected
and working.

Signed-off-by: Luca Leonardo Scorcia <l.scorcia@gmail.com>
---
Relevant bit of the stock source driver at [1].

Credits for noticing the issue and finding its cause go to matemiller992
on the postmarketOS forums, I cannot provide tags as he wants to stay
anonymous.

[1] https://github.com/lscorcia/linux-lenovo-tb7104f/blob/2dad69c9f28611ac6d3db2f1ee11b480a60d83ee/kernel-4.4/drivers/input/touchscreen/mediatek/gt912_p98996/gt9xx_driver.c#L1529

 drivers/input/touchscreen/goodix_fwupload.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/input/touchscreen/goodix_fwupload.c b/drivers/input/touchscreen/goodix_fwupload.c
index 5ae9a109ba0d..01e7705ef515 100644
--- a/drivers/input/touchscreen/goodix_fwupload.c
+++ b/drivers/input/touchscreen/goodix_fwupload.c
@@ -155,6 +155,7 @@ static int goodix_enter_upload_mode(struct i2c_client *client)
 
 static int goodix_start_firmware(struct i2c_client *client)
 {
+	struct goodix_ts_data *ts = i2c_get_clientdata(client);
 	int error;
 	u8 val;
 
@@ -168,6 +169,10 @@ static int goodix_start_firmware(struct i2c_client *client)
 	if (error)
 		return error;
 
+	error = goodix_int_sync(ts);
+	if (error)
+		return error;
+
 	error = goodix_i2c_read(client, GOODIX_REG_SW_WDT, &val, 1);
 	if (error)
 		return error;
-- 
2.43.0