clk: rockchip: implement the fraction divider branch type

Rockchip SoCs may provide fraction dividers for some clocks, mostly for
i2s and uarts. In contrast to the other registers, these do not use
the hiword-mask paradigm, but instead split the register into the upper
16 bit for the nominator and the lower 16 bit for the denominator.

The common clock framework got a generic fractional divider clock type
recently that can accomodate this setting easily. All currently known
fraction dividers have a separate gate too, therefore implement the
divider as composite using the ops-struct from fractional_divider clock
and add the gate if necessary.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/rockchip/clk.c

@@ -103,6 +103,54 @@ struct clk *rockchip_clk_register_branch(const char *name,
 	return clk;
 }
 
+static struct clk *rockchip_clk_register_frac_branch(const char *name,
+		const char **parent_names, u8 num_parents, void __iomem *base,
+		int muxdiv_offset, u8 div_flags,
+		int gate_offset, u8 gate_shift, u8 gate_flags,
+		unsigned long flags, spinlock_t *lock)
+{
+	struct clk *clk;
+	struct clk_gate *gate = NULL;
+	struct clk_fractional_divider *div = NULL;
+	const struct clk_ops *div_ops = NULL, *gate_ops = NULL;
+
+	if (gate_offset >= 0) {
+		gate = kzalloc(sizeof(*gate), GFP_KERNEL);
+		if (!gate)
+			return ERR_PTR(-ENOMEM);
+
+		gate->flags = gate_flags;
+		gate->reg = base + gate_offset;
+		gate->bit_idx = gate_shift;
+		gate->lock = lock;
+		gate_ops = &clk_gate_ops;
+	}
+
+	if (muxdiv_offset < 0)
+		return ERR_PTR(-EINVAL);
+
+	div = kzalloc(sizeof(*div), GFP_KERNEL);
+	if (!div)
+		return ERR_PTR(-ENOMEM);
+
+	div->flags = div_flags;
+	div->reg = base + muxdiv_offset;
+	div->mshift = 16;
+	div->mmask = 0xffff0000;
+	div->nshift = 0;
+	div->nmask = 0xffff;
+	div->lock = lock;
+	div_ops = &clk_fractional_divider_ops;
+
+	clk = clk_register_composite(NULL, name, parent_names, num_parents,
+				     NULL, NULL,
+				     &div->hw, div_ops,
+				     gate ? &gate->hw : NULL, gate_ops,
+				     flags);
+
+	return clk;
+}
+
 static DEFINE_SPINLOCK(clk_lock);
 static struct clk **clk_table;
 static void __iomem *reg_base;
@@ -197,8 +245,14 @@ void __init rockchip_clk_register_branches(
 					list->div_flags, &clk_lock);
 			break;
 		case branch_fraction_divider:
-			/* unimplemented */
-			continue;
+			/* keep all gates untouched for now */
+			flags |= CLK_IGNORE_UNUSED;
+
+			clk = rockchip_clk_register_frac_branch(list->name,
+				list->parent_names, list->num_parents,
+				reg_base, list->muxdiv_offset, list->div_flags,
+				list->gate_offset, list->gate_shift,
+				list->gate_flags, flags, &clk_lock);
 			break;
 		case branch_gate:
 			flags |= CLK_SET_RATE_PARENT;