usb: typec: tipd: Clear interrupts first

Right now the interrupt handler first reads all updated status registers
and only then clears the interrupts. It's possible that a duplicate
interrupt for a changed register or plug state comes in after the
interrupts have been processed but before they have been cleared:

* plug is inserted, TPS_REG_INT_PLUG_EVENT is set
* TPS_REG_INT_EVENT1 is read
* tps6598x_handle_plug_event() has run and registered the plug
* plug is removed again, TPS_REG_INT_PLUG_EVENT is set (again)
* TPS_REG_INT_CLEAR1 is written, TPS_REG_INT_PLUG_EVENT is cleared

We then have no plug connected and no pending interrupt but the tipd
core still thinks there is a plug. It's possible to trigger this with
e.g. a slightly broken Type-C to USB A converter.

Fix this by first clearing the interrupts and only then reading the
updated registers.

Fixes: 45188f2 ("usb: typec: tipd: Add support for Apple CD321X")
Fixes: 0a4c005 ("usb: typec: driver for TI TPS6598x USB Power Delivery controllers")
Cc: stable <stable@kernel.org>
Signed-off-by: Sven Peter <sven@svenpeter.dev>

Author: svenpeter42

drivers/usb/typec/tipd/core.c

@@ -550,24 +550,23 @@ static irqreturn_t cd321x_interrupt(int irq, void *data)
 	if (!event)
 		goto err_unlock;
 
+	tps6598x_write64(tps, TPS_REG_INT_CLEAR1, event);
+
 	if (!tps6598x_read_status(tps, &status))
-		goto err_clear_ints;
+		goto err_unlock;
 
 	if (event & APPLE_CD_REG_INT_POWER_STATUS_UPDATE)
 		if (!tps6598x_read_power_status(tps))
-			goto err_clear_ints;
+			goto err_unlock;
 
 	if (event & APPLE_CD_REG_INT_DATA_STATUS_UPDATE)
 		if (!tps6598x_read_data_status(tps))
-			goto err_clear_ints;
+			goto err_unlock;
 
 	/* Handle plug insert or removal */
 	if (event & APPLE_CD_REG_INT_PLUG_EVENT)
 		tps6598x_handle_plug_event(tps, status);
 
-err_clear_ints:
-	tps6598x_write64(tps, TPS_REG_INT_CLEAR1, event);
-
 err_unlock:
 	mutex_unlock(&tps->lock);
 
@@ -673,25 +672,24 @@ static irqreturn_t tps6598x_interrupt(int irq, void *data)
 	if (!(event1[0] | event1[1] | event2[0] | event2[1]))
 		goto err_unlock;
 
+	tps6598x_block_write(tps, TPS_REG_INT_CLEAR1, event1, intev_len);
+	tps6598x_block_write(tps, TPS_REG_INT_CLEAR2, event2, intev_len);
+
 	if (!tps6598x_read_status(tps, &status))
-		goto err_clear_ints;
+		goto err_unlock;
 
 	if ((event1[0] | event2[0]) & TPS_REG_INT_POWER_STATUS_UPDATE)
 		if (!tps6598x_read_power_status(tps))
-			goto err_clear_ints;
+			goto err_unlock;
 
 	if ((event1[0] | event2[0]) & TPS_REG_INT_DATA_STATUS_UPDATE)
 		if (!tps6598x_read_data_status(tps))
-			goto err_clear_ints;
+			goto err_unlock;
 
 	/* Handle plug insert or removal */
 	if ((event1[0] | event2[0]) & TPS_REG_INT_PLUG_EVENT)
 		tps6598x_handle_plug_event(tps, status);
 
-err_clear_ints:
-	tps6598x_block_write(tps, TPS_REG_INT_CLEAR1, event1, intev_len);
-	tps6598x_block_write(tps, TPS_REG_INT_CLEAR2, event2, intev_len);
-
 err_unlock:
 	mutex_unlock(&tps->lock);