clk: sunxi: Add Allwinner A20/A31 GMAC clock unit

The Allwinner A20/A31 clock module controls the transmit clock source
and interface type of the GMAC ethernet controller. Model this as
a single clock for GMAC drivers to use.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Emilio López <emilio@elopez.com.ar>

Documentation/devicetree/bindings/clock/sunxi.txt

@@ -38,6 +38,7 @@ Required properties:
 	"allwinner,sun6i-a31-apb2-gates-clk" - for the APB2 gates on A31
 	"allwinner,sun4i-mod0-clk" - for the module 0 family of clocks
 	"allwinner,sun7i-a20-out-clk" - for the external output clocks
+	"allwinner,sun7i-a20-gmac-clk" - for the GMAC clock module on A20/A31
 	"allwinner,sun4i-a10-usb-clk" - for usb gates + resets on A10 / A20
 	"allwinner,sun5i-a13-usb-clk" - for usb gates + resets on A13
 
@@ -56,6 +57,9 @@ Required properties for all clocks:
 And "allwinner,*-usb-clk" clocks also require:
 - reset-cells : shall be set to 1
 
+For "allwinner,sun7i-a20-gmac-clk", the parent clocks shall be fixed rate
+dummy clocks at 25 MHz and 125 MHz, respectively. See example.
+
 Clock consumers should specify the desired clocks they use with a
 "clocks" phandle cell. Consumers that are using a gated clock should
 provide an additional ID in their clock property. This ID is the
@@ -102,3 +106,29 @@ mmc0_clk: clk@01c20088 {
 	clocks = <&osc24M>, <&pll6 1>, <&pll5 1>;
 	clock-output-names = "mmc0";
 };
+
+mii_phy_tx_clk: clk@2 {
+	#clock-cells = <0>;
+	compatible = "fixed-clock";
+	clock-frequency = <25000000>;
+	clock-output-names = "mii_phy_tx";
+};
+
+gmac_int_tx_clk: clk@3 {
+	#clock-cells = <0>;
+	compatible = "fixed-clock";
+	clock-frequency = <125000000>;
+	clock-output-names = "gmac_int_tx";
+};
+
+gmac_clk: clk@01c20164 {
+	#clock-cells = <0>;
+	compatible = "allwinner,sun7i-a20-gmac-clk";
+	reg = <0x01c20164 0x4>;
+	/*
+	 * The first clock must be fixed at 25MHz;
+	 * the second clock must be fixed at 125MHz
+	 */
+	clocks = <&mii_phy_tx_clk>, <&gmac_int_tx_clk>;
+	clock-output-names = "gmac";
+};

drivers/clk/sunxi/clk-sunxi.c

@@ -410,6 +410,102 @@ static void sun7i_a20_get_out_factors(u32 *freq, u32 parent_rate,
 
 
 
+/**
+ * sun7i_a20_gmac_clk_setup - Setup function for A20/A31 GMAC clock module
+ *
+ * This clock looks something like this
+ *                               ________________________
+ *  MII TX clock from PHY >-----|___________    _________|----> to GMAC core
+ *  GMAC Int. RGMII TX clk >----|___________\__/__gate---|----> to PHY
+ *  Ext. 125MHz RGMII TX clk >--|__divider__/            |
+ *                              |________________________|
+ *
+ * The external 125 MHz reference is optional, i.e. GMAC can use its
+ * internal TX clock just fine. The A31 GMAC clock module does not have
+ * the divider controls for the external reference.
+ *
+ * To keep it simple, let the GMAC use either the MII TX clock for MII mode,
+ * and its internal TX clock for GMII and RGMII modes. The GMAC driver should
+ * select the appropriate source and gate/ungate the output to the PHY.
+ *
+ * Only the GMAC should use this clock. Altering the clock so that it doesn't
+ * match the GMAC's operation parameters will result in the GMAC not being
+ * able to send traffic out. The GMAC driver should set the clock rate and
+ * enable/disable this clock to configure the required state. The clock
+ * driver then responds by auto-reparenting the clock.
+ */
+
+#define SUN7I_A20_GMAC_GPIT	2
+#define SUN7I_A20_GMAC_MASK	0x3
+#define SUN7I_A20_GMAC_PARENTS	2
+
+static void __init sun7i_a20_gmac_clk_setup(struct device_node *node)
+{
+	struct clk *clk;
+	struct clk_mux *mux;
+	struct clk_gate *gate;
+	const char *clk_name = node->name;
+	const char *parents[SUN7I_A20_GMAC_PARENTS];
+	void *reg;
+
+	if (of_property_read_string(node, "clock-output-names", &clk_name))
+		return;
+
+	/* allocate mux and gate clock structs */
+	mux = kzalloc(sizeof(struct clk_mux), GFP_KERNEL);
+	if (!mux)
+		return;
+
+	gate = kzalloc(sizeof(struct clk_gate), GFP_KERNEL);
+	if (!gate)
+		goto free_mux;
+
+	/* gmac clock requires exactly 2 parents */
+	parents[0] = of_clk_get_parent_name(node, 0);
+	parents[1] = of_clk_get_parent_name(node, 1);
+	if (!parents[0] || !parents[1])
+		goto free_gate;
+
+	reg = of_iomap(node, 0);
+	if (!reg)
+		goto free_gate;
+
+	/* set up gate and fixed rate properties */
+	gate->reg = reg;
+	gate->bit_idx = SUN7I_A20_GMAC_GPIT;
+	gate->lock = &clk_lock;
+	mux->reg = reg;
+	mux->mask = SUN7I_A20_GMAC_MASK;
+	mux->flags = CLK_MUX_INDEX_BIT;
+	mux->lock = &clk_lock;
+
+	clk = clk_register_composite(NULL, clk_name,
+			parents, SUN7I_A20_GMAC_PARENTS,
+			&mux->hw, &clk_mux_ops,
+			NULL, NULL,
+			&gate->hw, &clk_gate_ops,
+			0);
+
+	if (IS_ERR(clk))
+		goto iounmap_reg;
+
+	of_clk_add_provider(node, of_clk_src_simple_get, clk);
+	clk_register_clkdev(clk, clk_name, NULL);
+
+	return;
+
+iounmap_reg:
+	iounmap(reg);
+free_gate:
+	kfree(gate);
+free_mux:
+	kfree(mux);
+}
+CLK_OF_DECLARE(sun7i_a20_gmac, "allwinner,sun7i-a20-gmac-clk",
+		sun7i_a20_gmac_clk_setup);
+
+
+
 /**
  * sunxi_factors_clk_setup() - Setup function for factor clocks
  */