net: ipa: determine channel from event

Each event in an event ring describes the TRE whose completion
caused the event.  Currently, every event ring is dedicated to a
single channel, so the channel is easily derived from the event
ring.

An event ring can actually be shared by more than one channel
though, and to distinguish events for one channel from another, the
event structure contains a field indicating which channel the event
is associated with.

In gsi_event_trans(), use the channel ID in an event to determine
which channel the event is for.  This makes the channel pointer now
passed to that function irrelevant; pass the GSI pointer to that
function instead.

And although it shouldn't happen, warn if an event arrives that
records a channel ID that's not in use, or if the event does not
have a transaction associated with it.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ipa/gsi.c

@@ -1327,17 +1327,29 @@ static int gsi_irq_init(struct gsi *gsi, struct platform_device *pdev)
 }
 
 /* Return the transaction associated with a transfer completion event */
-static struct gsi_trans *gsi_event_trans(struct gsi_channel *channel,
-					 struct gsi_event *event)
+static struct gsi_trans *
+gsi_event_trans(struct gsi *gsi, struct gsi_event *event)
 {
+	u32 channel_id = event->chid;
+	struct gsi_channel *channel;
+	struct gsi_trans *trans;
 	u32 tre_offset;
 	u32 tre_index;
 
+	channel = &gsi->channel[channel_id];
+	if (WARN(!channel->gsi, "event has bad channel %u\n", channel_id))
+		return NULL;
+
 	/* Event xfer_ptr records the TRE it's associated with */
 	tre_offset = lower_32_bits(le64_to_cpu(event->xfer_ptr));
 	tre_index = gsi_ring_index(&channel->tre_ring, tre_offset);
 
-	return gsi_channel_trans_mapped(channel, tre_index);
+	trans = gsi_channel_trans_mapped(channel, tre_index);
+
+	if (WARN(!trans, "channel %u event with no transaction\n", channel_id))
+		return NULL;
+
+	return trans;
 }
 
 /**
@@ -1381,7 +1393,9 @@ static void gsi_evt_ring_rx_update(struct gsi_evt_ring *evt_ring, u32 index)
 	 */
 	old_index = ring->index;
 	event = gsi_ring_virt(ring, old_index);
-	trans = gsi_event_trans(channel, event);
+	trans = gsi_event_trans(channel->gsi, event);
+	if (!trans)
+		return;
 
 	/* Compute the number of events to process before we wrap,
 	 * and determine when we'll be done processing events.
@@ -1493,7 +1507,9 @@ static struct gsi_trans *gsi_channel_update(struct gsi_channel *channel)
 		return NULL;
 
 	/* Get the transaction for the latest completed event. */
-	trans = gsi_event_trans(channel, gsi_ring_virt(ring, index - 1));
+	trans = gsi_event_trans(gsi, gsi_ring_virt(ring, index - 1));
+	if (!trans)
+		return NULL;
 
 	/* For RX channels, update each completed transaction with the number
 	 * of bytes that were actually received.  For TX channels, report