mei: me: wait for power gating exit confirmation

Fix the hbm power gating state machine so it will wait till it receives
confirmation interrupt for the PG_ISOLATION_EXIT message.

In process of the suspend flow the devices first have to exit from the
power gating state (runtime pm resume).
If we do not handle the confirmation interrupt after sending
PG_ISOLATION_EXIT message, we may receive it already after the suspend
flow has changed the device state and interrupt will be interpreted as a
spurious event, consequently link reset will be invoked which will
prevent the device from completing the suspend flow

kernel: [6603] mei_reset:136: mei_me 0000:00:16.0: powering down: end of reset
kernel: [476] mei_me_irq_thread_handler:643: mei_me 0000:00:16.0: function called after ISR to handle the interrupt processing.
kernel: mei_me 0000:00:16.0: FW not ready: resetting

Cc: <[e-mail]> #3.18+
Cc: Gabriele Mazzotta <[e-mail]>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=86241
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=770397
Tested-by: Gabriele Mazzotta <[e-mail]>
Signed-off-by: Alexander Usyskin <[e-mail]>
Signed-off-by: Tomas Winkler <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/mei/client.c

···
 bool mei_hbuf_acquire(struct mei_device *dev)
 {
 	if (mei_pg_state(dev) == MEI_PG_ON ||
-	    dev->pg_event == MEI_PG_EVENT_WAIT) {
+	    mei_pg_in_transition(dev)) {
 		dev_dbg(dev->dev, "device is in pg\n");
 		return false;
 	}

drivers/misc/mei/hw-me.c

···
 	mutex_lock(&dev->device_lock);
 
 reply:
-	if (dev->pg_event == MEI_PG_EVENT_RECEIVED)
-		ret = mei_hbm_pg(dev, MEI_PG_ISOLATION_EXIT_RES_CMD);
+	if (dev->pg_event != MEI_PG_EVENT_RECEIVED) {
+		ret = -ETIME;
+		goto out;
+	}
+
+	dev->pg_event = MEI_PG_EVENT_INTR_WAIT;
+	ret = mei_hbm_pg(dev, MEI_PG_ISOLATION_EXIT_RES_CMD);
+	if (ret)
+		return ret;
+
+	mutex_unlock(&dev->device_lock);
+	wait_event_timeout(dev->wait_pg,
+		dev->pg_event == MEI_PG_EVENT_INTR_RECEIVED, timeout);
+	mutex_lock(&dev->device_lock);
+
+	if (dev->pg_event == MEI_PG_EVENT_INTR_RECEIVED)
+		ret = 0;
 	else
 		ret = -ETIME;
 
+out:
 	dev->pg_event = MEI_PG_EVENT_IDLE;
 	hw->pg_state = MEI_PG_OFF;
 
 	return ret;
+}
+
+/**
+ * mei_me_pg_in_transition - is device now in pg transition
+ *
+ * @dev: the device structure
+ *
+ * Return: true if in pg transition, false otherwise
+ */
+static bool mei_me_pg_in_transition(struct mei_device *dev)
+{
+	return dev->pg_event >= MEI_PG_EVENT_WAIT &&
+	       dev->pg_event <= MEI_PG_EVENT_INTR_WAIT;
 }
 
 /**
···
 		HBM_MINOR_VERSION_PGI);
 
 	return false;
+}
+
+/**
+ * mei_me_pg_intr - perform pg processing in interrupt thread handler
+ *
+ * @dev: the device structure
+ */
+static void mei_me_pg_intr(struct mei_device *dev)
+{
+	struct mei_me_hw *hw = to_me_hw(dev);
+
+	if (dev->pg_event != MEI_PG_EVENT_INTR_WAIT)
+		return;
+
+	dev->pg_event = MEI_PG_EVENT_INTR_RECEIVED;
+	hw->pg_state = MEI_PG_OFF;
+	if (waitqueue_active(&dev->wait_pg))
+		wake_up(&dev->wait_pg);
 }
 
 /**
···
 		goto end;
 	}
 
+	mei_me_pg_intr(dev);
+
 	/*  check if we need to start the dev */
 	if (!mei_host_is_ready(dev)) {
 		if (mei_hw_is_ready(dev)) {
···
 	/*
 	 * During PG handshake only allowed write is the replay to the
 	 * PG exit message, so block calling write function
-	 * if the pg state is not idle
+	 * if the pg event is in PG handshake
 	 */
-	if (dev->pg_event == MEI_PG_EVENT_IDLE) {
+	if (dev->pg_event != MEI_PG_EVENT_WAIT &&
+	    dev->pg_event != MEI_PG_EVENT_RECEIVED) {
 		rets = mei_irq_write_handler(dev, &complete_list);
 		dev->hbuf_is_ready = mei_hbuf_is_ready(dev);
 	}
···
 	.hw_config = mei_me_hw_config,
 	.hw_start = mei_me_hw_start,
 
+	.pg_in_transition = mei_me_pg_in_transition,
 	.pg_is_enabled = mei_me_pg_is_enabled,
 
 	.intr_clear = mei_me_intr_clear,

drivers/misc/mei/hw-txe.c

···
 }
 
 /**
+ * mei_txe_pg_in_transition - is device now in pg transition
+ *
+ * @dev: the device structure
+ *
+ * Return: true if in pg transition, false otherwise
+ */
+static bool mei_txe_pg_in_transition(struct mei_device *dev)
+{
+	return dev->pg_event == MEI_PG_EVENT_WAIT;
+}
+
+/**
  * mei_txe_pg_is_enabled - detect if PG is supported by HW
  *
  * @dev: the device structure
···
 	.hw_config = mei_txe_hw_config,
 	.hw_start = mei_txe_hw_start,
 
+	.pg_in_transition = mei_txe_pg_in_transition,
 	.pg_is_enabled = mei_txe_pg_is_enabled,
 
 	.intr_clear = mei_txe_intr_clear,

drivers/misc/mei/mei_dev.h

···
 
  * @fw_status        : get fw status registers
  * @pg_state         : power gating state of the device
+ * @pg_in_transition : is device now in pg transition
  * @pg_is_enabled    : is power gating enabled
 
  * @intr_clear       : clear pending interrupts
···
 
 	int (*fw_status)(struct mei_device *dev, struct mei_fw_status *fw_sts);
 	enum mei_pg_state (*pg_state)(struct mei_device *dev);
+	bool (*pg_in_transition)(struct mei_device *dev);
 	bool (*pg_is_enabled)(struct mei_device *dev);
 
 	void (*intr_clear)(struct mei_device *dev);
···
  * @MEI_PG_EVENT_IDLE: the driver is not in power gating transition
  * @MEI_PG_EVENT_WAIT: the driver is waiting for a pg event to complete
  * @MEI_PG_EVENT_RECEIVED: the driver received pg event
+ * @MEI_PG_EVENT_INTR_WAIT: the driver is waiting for a pg event interrupt
+ * @MEI_PG_EVENT_INTR_RECEIVED: the driver received pg event interrupt
  */
 enum mei_pg_event {
 	MEI_PG_EVENT_IDLE,
 	MEI_PG_EVENT_WAIT,
 	MEI_PG_EVENT_RECEIVED,
+	MEI_PG_EVENT_INTR_WAIT,
+	MEI_PG_EVENT_INTR_RECEIVED,
 };
 
 /**
···
 static inline enum mei_pg_state mei_pg_state(struct mei_device *dev)
 {
 	return dev->ops->pg_state(dev);
+}
+
+static inline bool mei_pg_in_transition(struct mei_device *dev)
+{
+	return dev->ops->pg_in_transition(dev);
 }
 
 static inline bool mei_pg_is_enabled(struct mei_device *dev)