Input: mpr121 - handle multiple bits change of status register

BugLink: http://bugs.launchpad.net/bugs/1732698

[ Upstream commit 08fea55e ]

This driver reports input events on their interrupts which are triggered
by the sensor's status register changes.  But only single bit change is
reported in the interrupt handler.  So if there are multiple bits are
changed at almost the same time, other press or release events are ignored.

This fixes it by detecting all changed bits in the status register.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/input/keyboard/mpr121_touchkey.c

@@ -87,7 +87,8 @@ static irqreturn_t mpr_touchkey_interrupt(int irq, void *dev_id)
 	struct mpr121_touchkey *mpr121 = dev_id;
 	struct i2c_client *client = mpr121->client;
 	struct input_dev *input = mpr121->input_dev;
-	unsigned int key_num, key_val, pressed;
+	unsigned long bit_changed;
+	unsigned int key_num;
 	int reg;
 
 	reg = i2c_smbus_read_byte_data(client, ELE_TOUCH_STATUS_1_ADDR);
@@ -105,19 +106,23 @@ static irqreturn_t mpr_touchkey_interrupt(int irq, void *dev_id)
 
 	reg &= TOUCH_STATUS_MASK;
 	/* use old press bit to figure out which bit changed */
-	key_num = ffs(reg ^ mpr121->statusbits) - 1;
-	pressed = reg & (1 << key_num);
+	bit_changed = reg ^ mpr121->statusbits;
 	mpr121->statusbits = reg;
+	for_each_set_bit(key_num, &bit_changed, mpr121->keycount) {
+		unsigned int key_val, pressed;
 
+		pressed = reg & BIT(key_num);
 		key_val = mpr121->keycodes[key_num];
 
 		input_event(input, EV_MSC, MSC_SCAN, key_num);
 		input_report_key(input, key_val, pressed);
-	input_sync(input);
 
 		dev_dbg(&client->dev, "key %d %d %s\n", key_num, key_val,
 			pressed ? "pressed" : "released");
 
+	}
+	input_sync(input);
+
 out:
 	return IRQ_HANDLED;
 }