Input: iqs5xx - accommodate bootloader latency

The bootloader NAK's all I2C communication after the first 64-byte
bulk write if the bus frequency is equal to 400 kHz. This prevents
the platform from pushing updated firmware to the device.

The vendor's USB bootloader programming dongle appears to insert a
delay between the "open" command and the first 64-byte bulk write.
Adding a similar delay to the driver seems to eliminate the issue.

Furthermore, the dongle does not access the bootloader immediately
after powering up the device. Follow suit by adding a delay before
the "open" command to avoid wasted retries at 400 kHz.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Link: https://lore.kernel.org/r/1611002626-5889-4-git-send-email-jeff@labundy.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/iqs5xx.c

@@ -336,11 +336,16 @@ static int iqs5xx_bl_open(struct i2c_client *client)
 	 */
 	for (i = 0; i < IQS5XX_BL_ATTEMPTS; i++) {
 		iqs5xx_reset(client);
+		usleep_range(350, 400);
 
 		for (j = 0; j < IQS5XX_NUM_RETRIES; j++) {
 			error = iqs5xx_bl_cmd(client, IQS5XX_BL_CMD_VER, 0);
-			if (!error || error == -EINVAL)
-				return error;
+			if (!error)
+				usleep_range(10000, 10100);
+			else if (error != -EINVAL)
+				continue;
+
+			return error;
 		}
 	}