clk: basic clock hardware types

Many platforms support simple gateable clocks, fixed-rate clocks,
adjustable divider clocks and multi-parent multiplexer clocks.

This patch introduces basic clock types for the above-mentioned hardware
which share some common characteristics.

Based on original work by Jeremy Kerr and contribution by Jamie Iles.
Dividers and multiplexor clocks originally contributed by Richard Zhao &
Sascha Hauer.

Signed-off-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Mike Turquette <mturquette@ti.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Rob Herring <rob.herring@calxeda.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Jeremy Kerr <jeremy.kerr@canonical.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergman <arnd.bergmann@linaro.org>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Shawn Guo <shawn.guo@freescale.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Jamie Iles <jamie@jamieiles.com>
Cc: Richard Zhao <richard.zhao@linaro.org>
Cc: Saravana Kannan <skannan@codeaurora.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Amit Kucheria <amit.kucheria@linaro.org>
Cc: Deepak Saxena <dsaxena@linaro.org>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/clk/clk-gate.c

@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
+ * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
+ *
+ * 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.
+ *
+ * Gated clock implementation
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <linux/string.h>
+
+/**
+ * DOC: basic gatable clock which can gate and ungate it's ouput
+ *
+ * Traits of this clock:
+ * prepare - clk_(un)prepare only ensures parent is (un)prepared
+ * enable - clk_enable and clk_disable are functional & control gating
+ * rate - inherits rate from parent.  No clk_set_rate support
+ * parent - fixed parent.  No clk_set_parent support
+ */
+
+#define to_clk_gate(_hw) container_of(_hw, struct clk_gate, hw)
+
+static void clk_gate_set_bit(struct clk_gate *gate)
+{
+	u32 reg;
+	unsigned long flags = 0;
+
+	if (gate->lock)
+		spin_lock_irqsave(gate->lock, flags);
+
+	reg = readl(gate->reg);
+	reg |= BIT(gate->bit_idx);
+	writel(reg, gate->reg);
+
+	if (gate->lock)
+		spin_unlock_irqrestore(gate->lock, flags);
+}
+
+static void clk_gate_clear_bit(struct clk_gate *gate)
+{
+	u32 reg;
+	unsigned long flags = 0;
+
+	if (gate->lock)
+		spin_lock_irqsave(gate->lock, flags);
+
+	reg = readl(gate->reg);
+	reg &= ~BIT(gate->bit_idx);
+	writel(reg, gate->reg);
+
+	if (gate->lock)
+		spin_unlock_irqrestore(gate->lock, flags);
+}
+
+static int clk_gate_enable(struct clk_hw *hw)
+{
+	struct clk_gate *gate = to_clk_gate(hw);
+
+	if (gate->flags & CLK_GATE_SET_TO_DISABLE)
+		clk_gate_clear_bit(gate);
+	else
+		clk_gate_set_bit(gate);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(clk_gate_enable);
+
+static void clk_gate_disable(struct clk_hw *hw)
+{
+	struct clk_gate *gate = to_clk_gate(hw);
+
+	if (gate->flags & CLK_GATE_SET_TO_DISABLE)
+		clk_gate_set_bit(gate);
+	else
+		clk_gate_clear_bit(gate);
+}
+EXPORT_SYMBOL_GPL(clk_gate_disable);
+
+static int clk_gate_is_enabled(struct clk_hw *hw)
+{
+	u32 reg;
+	struct clk_gate *gate = to_clk_gate(hw);
+
+	reg = readl(gate->reg);
+
+	/* if a set bit disables this clk, flip it before masking */
+	if (gate->flags & CLK_GATE_SET_TO_DISABLE)
+		reg ^= BIT(gate->bit_idx);
+
+	reg &= BIT(gate->bit_idx);
+
+	return reg ? 1 : 0;
+}
+EXPORT_SYMBOL_GPL(clk_gate_is_enabled);
+
+struct clk_ops clk_gate_ops = {
+	.enable = clk_gate_enable,
+	.disable = clk_gate_disable,
+	.is_enabled = clk_gate_is_enabled,
+};
+EXPORT_SYMBOL_GPL(clk_gate_ops);
+
+struct clk *clk_register_gate(struct device *dev, const char *name,
+		const char *parent_name, unsigned long flags,
+		void __iomem *reg, u8 bit_idx,
+		u8 clk_gate_flags, spinlock_t *lock)
+{
+	struct clk_gate *gate;
+	struct clk *clk;
+
+	gate = kzalloc(sizeof(struct clk_gate), GFP_KERNEL);
+
+	if (!gate) {
+		pr_err("%s: could not allocate gated clk\n", __func__);
+		return NULL;
+	}
+
+	/* struct clk_gate assignments */
+	gate->reg = reg;
+	gate->bit_idx = bit_idx;
+	gate->flags = clk_gate_flags;
+	gate->lock = lock;
+
+	if (parent_name) {
+		gate->parent[0] = kstrdup(parent_name, GFP_KERNEL);
+		if (!gate->parent[0])
+			goto out;
+	}
+
+	clk = clk_register(dev, name,
+			&clk_gate_ops, &gate->hw,
+			gate->parent,
+			(parent_name ? 1 : 0),
+			flags);
+	if (clk)
+		return clk;
+out:
+	kfree(gate->parent[0]);
+	kfree(gate);
+
+	return NULL;
+}