bus: mhi: ep: Add support for powering down the MHI endpoint stack

Add support for MHI endpoint power_down that includes stopping all
available channels, destroying the channels, resetting the event and
transfer rings and freeing the host cache.

The stack will be powered down whenever the physical bus link goes down.
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

drivers/bus/mhi/ep/main.c

@@ -22,6 +22,8 @@
 
 static DEFINE_IDA(mhi_ep_cntrl_ida);
 
+static int mhi_ep_destroy_device(struct device *dev, void *data);
+
 static int mhi_ep_send_event(struct mhi_ep_cntrl *mhi_cntrl, u32 ring_idx,
 			     struct mhi_ring_element *el, bool bei)
 {
@@ -400,6 +402,68 @@ static irqreturn_t mhi_ep_irq(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+static void mhi_ep_abort_transfer(struct mhi_ep_cntrl *mhi_cntrl)
+{
+	struct mhi_ep_ring *ch_ring, *ev_ring;
+	struct mhi_result result = {};
+	struct mhi_ep_chan *mhi_chan;
+	int i;
+
+	/* Stop all the channels */
+	for (i = 0; i < mhi_cntrl->max_chan; i++) {
+		mhi_chan = &mhi_cntrl->mhi_chan[i];
+		if (!mhi_chan->ring.started)
+			continue;
+
+		mutex_lock(&mhi_chan->lock);
+		/* Send channel disconnect status to client drivers */
+		if (mhi_chan->xfer_cb) {
+			result.transaction_status = -ENOTCONN;
+			result.bytes_xferd = 0;
+			mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
+		}
+
+		mhi_chan->state = MHI_CH_STATE_DISABLED;
+		mutex_unlock(&mhi_chan->lock);
+	}
+
+	flush_workqueue(mhi_cntrl->wq);
+
+	/* Destroy devices associated with all channels */
+	device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_ep_destroy_device);
+
+	/* Stop and reset the transfer rings */
+	for (i = 0; i < mhi_cntrl->max_chan; i++) {
+		mhi_chan = &mhi_cntrl->mhi_chan[i];
+		if (!mhi_chan->ring.started)
+			continue;
+
+		ch_ring = &mhi_cntrl->mhi_chan[i].ring;
+		mutex_lock(&mhi_chan->lock);
+		mhi_ep_ring_reset(mhi_cntrl, ch_ring);
+		mutex_unlock(&mhi_chan->lock);
+	}
+
+	/* Stop and reset the event rings */
+	for (i = 0; i < mhi_cntrl->event_rings; i++) {
+		ev_ring = &mhi_cntrl->mhi_event[i].ring;
+		if (!ev_ring->started)
+			continue;
+
+		mutex_lock(&mhi_cntrl->event_lock);
+		mhi_ep_ring_reset(mhi_cntrl, ev_ring);
+		mutex_unlock(&mhi_cntrl->event_lock);
+	}
+
+	/* Stop and reset the command ring */
+	mhi_ep_ring_reset(mhi_cntrl, &mhi_cntrl->mhi_cmd->ring);
+
+	mhi_ep_free_host_cfg(mhi_cntrl);
+	mhi_ep_mmio_mask_interrupts(mhi_cntrl);
+
+	mhi_cntrl->enabled = false;
+}
+
 int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
 {
 	struct device *dev = &mhi_cntrl->mhi_dev->dev;
@@ -454,6 +518,16 @@ int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
 }
 EXPORT_SYMBOL_GPL(mhi_ep_power_up);
 
+void mhi_ep_power_down(struct mhi_ep_cntrl *mhi_cntrl)
+{
+	if (mhi_cntrl->enabled)
+		mhi_ep_abort_transfer(mhi_cntrl);
+
+	kfree(mhi_cntrl->mhi_event);
+	disable_irq(mhi_cntrl->irq);
+}
+EXPORT_SYMBOL_GPL(mhi_ep_power_down);
+
 static void mhi_ep_release_device(struct device *dev)
 {
 	struct mhi_ep_device *mhi_dev = to_mhi_ep_device(dev);
@@ -733,6 +807,10 @@ int mhi_ep_register_controller(struct mhi_ep_cntrl *mhi_cntrl,
 }
 EXPORT_SYMBOL_GPL(mhi_ep_register_controller);
 
+/*
+ * It is expected that the controller drivers will power down the MHI EP stack
+ * using "mhi_ep_power_down()" before calling this function to unregister themselves.
+ */
 void mhi_ep_unregister_controller(struct mhi_ep_cntrl *mhi_cntrl)
 {
 	struct mhi_ep_device *mhi_dev = mhi_cntrl->mhi_dev;

include/linux/mhi_ep.h

@@ -244,4 +244,10 @@ void mhi_ep_unregister_controller(struct mhi_ep_cntrl *mhi_cntrl);
  */
 int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl);
 
+/**
+ * mhi_ep_power_down - Power down the MHI endpoint stack
+ * @mhi_cntrl: MHI controller
+ */
+void mhi_ep_power_down(struct mhi_ep_cntrl *mhi_cntrl);
+
 #endif