net: xilinx: axiethernet: Introduce helper functions for MDC enable/disable

Introduce helper functions to enable/disable MDIO interface clock. This
change serves a preparatory patch for the coming feature to dynamically
control the management bus clock.
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/xilinx/xilinx_axienet.h

@@ -378,6 +378,7 @@ struct axidma_bd {
  * @dev:	Pointer to device structure
  * @phy_node:	Pointer to device node structure
  * @mii_bus:	Pointer to MII bus structure
+ * @mii_clk_div: MII bus clock divider value
  * @regs_start: Resource start for axienet device addresses
  * @regs:	Base address for the axienet_local device address space
  * @dma_regs:	Base address for the axidma device address space
@@ -427,6 +428,7 @@ struct axienet_local {
 
 	/* MDIO bus data */
 	struct mii_bus *mii_bus;	/* MII bus reference */
+	u8 mii_clk_div; /* MII bus clock divider value */
 
 	/* IO registers, dma functions and IRQs */
 	resource_size_t regs_start;

drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c

@@ -30,6 +30,23 @@ static int axienet_mdio_wait_until_ready(struct axienet_local *lp)
 				  1, 20000);
 }
 
+/* Enable the MDIO MDC. Called prior to a read/write operation */
+static void axienet_mdio_mdc_enable(struct axienet_local *lp)
+{
+	axienet_iow(lp, XAE_MDIO_MC_OFFSET,
+		    ((u32)lp->mii_clk_div | XAE_MDIO_MC_MDIOEN_MASK));
+}
+
+/* Disable the MDIO MDC. Called after a read/write operation*/
+static void axienet_mdio_mdc_disable(struct axienet_local *lp)
+{
+	u32 mc_reg;
+
+	mc_reg = axienet_ior(lp, XAE_MDIO_MC_OFFSET);
+	axienet_iow(lp, XAE_MDIO_MC_OFFSET,
+		    (mc_reg & ~XAE_MDIO_MC_MDIOEN_MASK));
+}
+
 /**
  * axienet_mdio_read - MDIO interface read function
  * @bus:	Pointer to mii bus structure
@@ -124,7 +141,9 @@ static int axienet_mdio_write(struct mii_bus *bus, int phy_id, int reg,
  **/
 int axienet_mdio_enable(struct axienet_local *lp)
 {
-	u32 clk_div, host_clock;
+	u32 host_clock;
+
+	lp->mii_clk_div = 0;
 
 	if (lp->clk) {
 		host_clock = clk_get_rate(lp->clk);
@@ -176,19 +195,19 @@ int axienet_mdio_enable(struct axienet_local *lp)
 	 * "clock-frequency" from the CPU
 	 */
 
-	clk_div = (host_clock / (MAX_MDIO_FREQ * 2)) - 1;
+	lp->mii_clk_div = (host_clock / (MAX_MDIO_FREQ * 2)) - 1;
 	/* If there is any remainder from the division of
 	 * fHOST / (MAX_MDIO_FREQ * 2), then we need to add
 	 * 1 to the clock divisor or we will surely be above 2.5 MHz
 	 */
 	if (host_clock % (MAX_MDIO_FREQ * 2))
-		clk_div++;
+		lp->mii_clk_div++;
 
 	netdev_dbg(lp->ndev,
 		   "Setting MDIO clock divisor to %u/%u Hz host clock.\n",
-		   clk_div, host_clock);
+		   lp->mii_clk_div, host_clock);
 
-	axienet_iow(lp, XAE_MDIO_MC_OFFSET, clk_div | XAE_MDIO_MC_MDIOEN_MASK);
+	axienet_iow(lp, XAE_MDIO_MC_OFFSET, lp->mii_clk_div | XAE_MDIO_MC_MDIOEN_MASK);
 
 	return axienet_mdio_wait_until_ready(lp);
 }