i2c: ocores: do not handle IRQ if IF is not set

If the Interrupt Flag (IF) is not set, we should not handle the IRQ:
- the line can be shared with other devices
- it can be a spurious interrupt

To avoid reading twice the status register, the ocores_process() function
expects it to be read by the caller.
Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
Acked-by: Peter Korsgaard <peter@korsgaard.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-ocores.c

@@ -143,10 +143,9 @@ static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
 	return i2c->getreg(i2c, reg);
 }
 
-static void ocores_process(struct ocores_i2c *i2c)
+static void ocores_process(struct ocores_i2c *i2c, u8 stat)
 {
 	struct i2c_msg *msg = i2c->msg;
-	u8 stat = oc_getreg(i2c, OCI2C_STATUS);
 	unsigned long flags;
 
 	/*
@@ -223,8 +222,12 @@ static void ocores_process(struct ocores_i2c *i2c)
 static irqreturn_t ocores_isr(int irq, void *dev_id)
 {
 	struct ocores_i2c *i2c = dev_id;
+	u8 stat = oc_getreg(i2c, OCI2C_STATUS);
+
+	if (!(stat & OCI2C_STAT_IF))
+		return IRQ_NONE;
 
-	ocores_process(i2c);
+	ocores_process(i2c, stat);
 
 	return IRQ_HANDLED;
 }