i2c-designware: Support multiple cores using same ISR

Add check to make sure that the core is enabled and has outstanding
interrupts. The activity bit is masked due to the fact that it will
stay active even after the controller has been disabled until the
contoller internal state machines have settled.

Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

drivers/i2c/busses/i2c-designware-core.c

@@ -521,10 +521,16 @@ static u32 i2c_dw_read_clear_intrbits(struct dw_i2c_dev *dev)
 irqreturn_t i2c_dw_isr(int this_irq, void *dev_id)
 {
 	struct dw_i2c_dev *dev = dev_id;
-	u32 stat;
+	u32 stat, enabled;
+
+	enabled = dw_readl(dev, DW_IC_ENABLE);
+	stat = dw_readl(dev, DW_IC_RAW_INTR_STAT);
+	dev_dbg(dev->dev, "%s:  %s enabled= 0x%x stat=0x%x\n", __func__,
+		dev->adapter.name, enabled, stat);
+	if (!enabled || !(stat & ~DW_IC_INTR_ACTIVITY))
+		return IRQ_NONE;
 
 	stat = i2c_dw_read_clear_intrbits(dev);
-	dev_dbg(dev->dev, "%s: stat=0x%x\n", __func__, stat);
 
 	if (stat & DW_IC_INTR_TX_ABRT) {
 		dev->cmd_err |= DW_IC_ERR_TX_ABRT;