sparc64: ensure LDC channel is ready before communication

Ensure that LDC channel is up before writing to it, in RAW mode. Generate
event to bring the LDC channel up, if it's not up already.

Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Reviewed-by: Aaron Young <aaron.young@oracle.com>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/ldc.c

@@ -813,9 +813,14 @@ static irqreturn_t ldc_rx(int irq, void *dev_id)
 		lp->hs_state = LDC_HS_COMPLETE;
 		ldc_set_state(lp, LDC_STATE_CONNECTED);
 
-		event_mask |= LDC_EVENT_UP;
-
-		orig_state = lp->chan_state;
+		/*
+		 * Generate an LDC_EVENT_UP event if the channel
+		 * was not already up.
+		 */
+		if (orig_state != LDC_CHANNEL_UP) {
+			event_mask |= LDC_EVENT_UP;
+			orig_state = lp->chan_state;
+		}
 	}
 
 	/* If we are in reset state, flush the RX queue and ignore
@@ -929,7 +934,14 @@ static irqreturn_t ldc_tx(int irq, void *dev_id)
 		lp->hs_state = LDC_HS_COMPLETE;
 		ldc_set_state(lp, LDC_STATE_CONNECTED);
 
-		event_mask |= LDC_EVENT_UP;
+		/*
+		 * Generate an LDC_EVENT_UP event if the channel
+		 * was not already up.
+		 */
+		if (orig_state != LDC_CHANNEL_UP) {
+			event_mask |= LDC_EVENT_UP;
+			orig_state = lp->chan_state;
+		}
 	}
 
 	spin_unlock_irqrestore(&lp->lock, flags);
@@ -1475,9 +1487,17 @@ void __ldc_print(struct ldc_channel *lp, const char *caller)
 static int write_raw(struct ldc_channel *lp, const void *buf, unsigned int size)
 {
 	struct ldc_packet *p;
-	unsigned long new_tail;
+	unsigned long new_tail, hv_err;
 	int err;
 
+	hv_err = sun4v_ldc_tx_get_state(lp->id, &lp->tx_head, &lp->tx_tail,
+					&lp->chan_state);
+	if (unlikely(hv_err))
+		return -EBUSY;
+
+	if (unlikely(lp->chan_state != LDC_CHANNEL_UP))
+		return LDC_ABORT(lp);
+
 	if (size > LDC_PACKET_SIZE)
 		return -EMSGSIZE;