net: phy: qsemi: remove the use of .ack_interrupt()

In preparation of removing the .ack_interrupt() callback, we must replace
its occurrences (aka phy_clear_interrupt), from the 2 places where it is
called from (phy_enable_interrupts and phy_disable_interrupts), with
equivalent functionality.

This means that clearing interrupts now becomes something that the PHY
driver is responsible of doing, before enabling interrupts and after
clearing them. Make this driver follow the new contract.

Also, add a comment describing the multiple step interrupt
acknoledgement process.

Signed-off-by: Ioana Ciornei <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/qsemi.c

···
 {
 	int err;
 
+	/* The Interrupt Source register is not self-clearing, bits 4 and 5 are
+	 * cleared when MII_BMSR is read and bits 1 and 3 are cleared when
+	 * MII_EXPANSION is read
+	 */
 	err = phy_read(phydev, MII_QS6612_ISR);
 
 	if (err < 0)
···
 static int qs6612_config_intr(struct phy_device *phydev)
 {
 	int err;
-	if (phydev->interrupts == PHY_INTERRUPT_ENABLED)
+	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
+		/* clear any interrupts before enabling them */
+		err = qs6612_ack_interrupt(phydev);
+		if (err)
+			return err;
+
 		err = phy_write(phydev, MII_QS6612_IMR,
 				MII_QS6612_IMR_INIT);
-	else
+	} else {
 		err = phy_write(phydev, MII_QS6612_IMR, 0);
+		if (err)
+			return err;
+
+		/* clear any leftover interrupts */
+		err = qs6612_ack_interrupt(phydev);
+	}
 
 	return err;
 
···
 	.phy_id_mask	= 0xfffffff0,
 	/* PHY_BASIC_FEATURES */
 	.config_init	= qs6612_config_init,
-	.ack_interrupt	= qs6612_ack_interrupt,
 	.config_intr	= qs6612_config_intr,
 	.handle_interrupt = qs6612_handle_interrupt,
 } };