clk: shmobile: Add R-Car Gen2 ADSP clock support

Add the ADSP clock support to the R-Car generation 2 CPG driver.  This clock
gets derived from  PLL1.  The layout of the ADSPCKCR register is  similar to
those of the clocks supported by the 'clk-div6' driver but the divider encoding
is non-linear, so can't be supported by that driver...

Based on the original patch by Konstantin Kozhevnikov
<konstantin.kozhevnikov@cogentembedded.com>.
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Documentation/devicetree/bindings/clock/renesas,rcar-gen2-cpg-clocks.txt

@@ -18,7 +18,8 @@ Required Properties:
     to the USB_EXTAL clock
   - #clock-cells: Must be 1
   - clock-output-names: The names of the clocks. Supported clocks are "main",
-    "pll0", "pll1", "pll3", "lb", "qspi", "sdh", "sd0", "sd1", "z", and "rcan"
+    "pll0", "pll1", "pll3", "lb", "qspi", "sdh", "sd0", "sd1", "z", "rcan", and
+    "adsp"
 
 
 Example
@@ -32,5 +33,5 @@ Example
 		#clock-cells = <1>;
 		clock-output-names = "main", "pll0, "pll1", "pll3",
 				     "lb", "qspi", "sdh", "sd0", "sd1", "z",
-				     "rcan";
+				     "rcan", "adsp";
 	};

drivers/clk/shmobile/clk-rcar-gen2.c

@@ -33,6 +33,7 @@ struct rcar_gen2_cpg {
 #define CPG_FRQCRC			0x000000e0
 #define CPG_FRQCRC_ZFC_MASK		(0x1f << 8)
 #define CPG_FRQCRC_ZFC_SHIFT		8
+#define CPG_ADSPCKCR			0x0000025c
 #define CPG_RCANCKCR			0x00000270
 
 /* -----------------------------------------------------------------------------
@@ -199,6 +200,51 @@ static struct clk * __init cpg_rcan_clk_register(struct rcar_gen2_cpg *cpg,
 	return clk;
 }
 
+/* ADSP divisors */
+static const struct clk_div_table cpg_adsp_div_table[] = {
+	{  1,  3 }, {  2,  4 }, {  3,  6 }, {  4,  8 },
+	{  5, 12 }, {  6, 16 }, {  7, 18 }, {  8, 24 },
+	{ 10, 36 }, { 11, 48 }, {  0,  0 },
+};
+
+static struct clk * __init cpg_adsp_clk_register(struct rcar_gen2_cpg *cpg)
+{
+	const char *parent_name = "pll1";
+	struct clk_divider *div;
+	struct clk_gate *gate;
+	struct clk *clk;
+
+	div = kzalloc(sizeof(*div), GFP_KERNEL);
+	if (!div)
+		return ERR_PTR(-ENOMEM);
+
+	div->reg = cpg->reg + CPG_ADSPCKCR;
+	div->width = 4;
+	div->table = cpg_adsp_div_table;
+	div->lock = &cpg->lock;
+
+	gate = kzalloc(sizeof(*gate), GFP_KERNEL);
+	if (!gate) {
+		kfree(div);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	gate->reg = cpg->reg + CPG_ADSPCKCR;
+	gate->bit_idx = 8;
+	gate->flags = CLK_GATE_SET_TO_DISABLE;
+	gate->lock = &cpg->lock;
+
+	clk = clk_register_composite(NULL, "adsp", &parent_name, 1, NULL, NULL,
+				     &div->hw, &clk_divider_ops,
+				     &gate->hw, &clk_gate_ops, 0);
+	if (IS_ERR(clk)) {
+		kfree(gate);
+		kfree(div);
+	}
+
+	return clk;
+}
+
 /* -----------------------------------------------------------------------------
  * CPG Clock Data
  */
@@ -303,6 +349,8 @@ rcar_gen2_cpg_register_clock(struct device_node *np, struct rcar_gen2_cpg *cpg,
 		return cpg_z_clk_register(cpg);
 	} else if (!strcmp(name, "rcan")) {
 		return cpg_rcan_clk_register(cpg, np);
+	} else if (!strcmp(name, "adsp")) {
+		return cpg_adsp_clk_register(cpg);
 	} else {
 		return ERR_PTR(-EINVAL);
 	}