ARM: imx: add an exclusive gate clock type

There are a couple of gate clocks are mutually exclusive on i.MX6, i.e.
LVDSCLK1_IBEN and LVDSCLK1_OBEN.  They cannot be enabled simultaneously.
This patches adds an exclusive gate clock type specifically for such
case.  The clock driver will need to call imx_clk_gate_exclusive() to
register a gate clock with parameter exclusive_mask indicating the mask
of gate bits which are mutually exclusive to this gate clock.

Right now, it only handles the exclusive gate clocks which are defined
in a single hardware register, which is the case we're running into
today.  But it can be extended to handle exclusive gate clocks defined
in different registers later if needed.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>

arch/arm/mach-imx/Makefile

@@ -16,7 +16,8 @@ obj-$(CONFIG_SOC_IMX5) += cpu-imx5.o clk-imx51-imx53.o $(imx5-pm-y)
 
 obj-$(CONFIG_COMMON_CLK) += clk-pllv1.o clk-pllv2.o clk-pllv3.o clk-gate2.o \
 			    clk-pfd.o clk-busy.o clk.o \
-			    clk-fixup-div.o clk-fixup-mux.o
+			    clk-fixup-div.o clk-fixup-mux.o \
+			    clk-gate-exclusive.o
 
 obj-$(CONFIG_IMX_HAVE_IOMUX_V1) += iomux-v1.o
 obj-$(CONFIG_ARCH_MXC_IOMUX_V3) += iomux-v3.o

arch/arm/mach-imx/clk-gate-exclusive.c

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2014 Freescale Semiconductor, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include "clk.h"
+
+/**
+ * struct clk_gate_exclusive - i.MX specific gate clock which is mutually
+ * exclusive with other gate clocks
+ *
+ * @gate: the parent class
+ * @exclusive_mask: mask of gate bits which are mutually exclusive to this
+ *	gate clock
+ *
+ * The imx exclusive gate clock is a subclass of basic clk_gate
+ * with an addtional mask to indicate which other gate bits in the same
+ * register is mutually exclusive to this gate clock.
+ */
+struct clk_gate_exclusive {
+	struct clk_gate gate;
+	u32 exclusive_mask;
+};
+
+static int clk_gate_exclusive_enable(struct clk_hw *hw)
+{
+	struct clk_gate *gate = container_of(hw, struct clk_gate, hw);
+	struct clk_gate_exclusive *exgate = container_of(gate,
+					struct clk_gate_exclusive, gate);
+	u32 val = readl(gate->reg);
+
+	if (val & exgate->exclusive_mask)
+		return -EBUSY;
+
+	return clk_gate_ops.enable(hw);
+}
+
+static void clk_gate_exclusive_disable(struct clk_hw *hw)
+{
+	clk_gate_ops.disable(hw);
+}
+
+static int clk_gate_exclusive_is_enabled(struct clk_hw *hw)
+{
+	return clk_gate_ops.is_enabled(hw);
+}
+
+static const struct clk_ops clk_gate_exclusive_ops = {
+	.enable = clk_gate_exclusive_enable,
+	.disable = clk_gate_exclusive_disable,
+	.is_enabled = clk_gate_exclusive_is_enabled,
+};
+
+struct clk *imx_clk_gate_exclusive(const char *name, const char *parent,
+	 void __iomem *reg, u8 shift, u32 exclusive_mask)
+{
+	struct clk_gate_exclusive *exgate;
+	struct clk_gate *gate;
+	struct clk *clk;
+	struct clk_init_data init;
+
+	if (exclusive_mask == 0)
+		return ERR_PTR(-EINVAL);
+
+	exgate = kzalloc(sizeof(*exgate), GFP_KERNEL);
+	if (!exgate)
+		return ERR_PTR(-ENOMEM);
+	gate = &exgate->gate;
+
+	init.name = name;
+	init.ops = &clk_gate_exclusive_ops;
+	init.flags = CLK_SET_RATE_PARENT;
+	init.parent_names = parent ? &parent : NULL;
+	init.num_parents = parent ? 1 : 0;
+
+	gate->reg = reg;
+	gate->bit_idx = shift;
+	gate->lock = &imx_ccm_lock;
+	gate->hw.init = &init;
+	exgate->exclusive_mask = exclusive_mask;
+
+	clk = clk_register(NULL, &gate->hw);
+	if (IS_ERR(clk))
+		kfree(exgate);
+
+	return clk;
+}

arch/arm/mach-imx/clk.h

@@ -36,6 +36,9 @@ struct clk *clk_register_gate2(struct device *dev, const char *name,
 struct clk * imx_obtain_fixed_clock(
 			const char *name, unsigned long rate);
 
+struct clk *imx_clk_gate_exclusive(const char *name, const char *parent,
+	 void __iomem *reg, u8 shift, u32 exclusive_mask);
+
 static inline struct clk *imx_clk_gate2(const char *name, const char *parent,
 		void __iomem *reg, u8 shift)
 {