ARM: imx: add common clock support for fixup div

One register may have several fields to control some clocks. It
is possible that the read/write values of some fields may map to
different real functional values, so writing to the other fields
in the same register may break a working clock tree. A real case
is the aclk_podf field in the register 'CCM Serial Clock Multiplexer
Register 1' of i.MX6Q/SDL SoC. This patch introduces a fixup hook
for divider clock which is called before writing a value to clock
registers to support this kind of divider clocks.

Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/Makefile

@@ -15,7 +15,8 @@ imx5-pm-$(CONFIG_PM) += pm-imx5.o
 obj-$(CONFIG_SOC_IMX5) += cpu-imx5.o mm-imx5.o clk-imx51-imx53.o ehci-imx5.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-pfd.o clk-busy.o clk.o \
+			    clk-fixup-div.o
 
 obj-$(CONFIG_IMX_HAVE_IOMUX_V1) += iomux-v1.o
 obj-$(CONFIG_ARCH_MXC_IOMUX_V3) += iomux-v3.o

arch/arm/mach-imx/clk-fixup-div.c

@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2013 Freescale Semiconductor, Inc.
+ *
+ * The code contained herein is licensed under the GNU General Public
+ * License. You may obtain a copy of the GNU General Public License
+ * Version 2 or later at the following locations:
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include "clk.h"
+
+#define to_clk_div(_hw) container_of(_hw, struct clk_divider, hw)
+#define div_mask(d)	((1 << (d->width)) - 1)
+
+/**
+ * struct clk_fixup_div - imx integer fixup divider clock
+ * @divider: the parent class
+ * @ops: pointer to clk_ops of parent class
+ * @fixup: a hook to fixup the write value
+ *
+ * The imx fixup divider clock is a subclass of basic clk_divider
+ * with an addtional fixup hook.
+ */
+struct clk_fixup_div {
+	struct clk_divider divider;
+	const struct clk_ops *ops;
+	void (*fixup)(u32 *val);
+};
+
+static inline struct clk_fixup_div *to_clk_fixup_div(struct clk_hw *hw)
+{
+	struct clk_divider *divider = to_clk_div(hw);
+
+	return container_of(divider, struct clk_fixup_div, divider);
+}
+
+static unsigned long clk_fixup_div_recalc_rate(struct clk_hw *hw,
+					 unsigned long parent_rate)
+{
+	struct clk_fixup_div *fixup_div = to_clk_fixup_div(hw);
+
+	return fixup_div->ops->recalc_rate(&fixup_div->divider.hw, parent_rate);
+}
+
+static long clk_fixup_div_round_rate(struct clk_hw *hw, unsigned long rate,
+			       unsigned long *prate)
+{
+	struct clk_fixup_div *fixup_div = to_clk_fixup_div(hw);
+
+	return fixup_div->ops->round_rate(&fixup_div->divider.hw, rate, prate);
+}
+
+static int clk_fixup_div_set_rate(struct clk_hw *hw, unsigned long rate,
+			    unsigned long parent_rate)
+{
+	struct clk_fixup_div *fixup_div = to_clk_fixup_div(hw);
+	struct clk_divider *div = to_clk_div(hw);
+	unsigned int divider, value;
+	unsigned long flags = 0;
+	u32 val;
+
+	divider = parent_rate / rate;
+
+	/* Zero based divider */
+	value = divider - 1;
+
+	if (value > div_mask(div))
+		value = div_mask(div);
+
+	spin_lock_irqsave(div->lock, flags);
+
+	val = readl(div->reg);
+	val &= ~(div_mask(div) << div->shift);
+	val |= value << div->shift;
+	fixup_div->fixup(&val);
+	writel(val, div->reg);
+
+	spin_unlock_irqrestore(div->lock, flags);
+
+	return 0;
+}
+
+static const struct clk_ops clk_fixup_div_ops = {
+	.recalc_rate = clk_fixup_div_recalc_rate,
+	.round_rate = clk_fixup_div_round_rate,
+	.set_rate = clk_fixup_div_set_rate,
+};
+
+struct clk *imx_clk_fixup_divider(const char *name, const char *parent,
+				  void __iomem *reg, u8 shift, u8 width,
+				  void (*fixup)(u32 *val))
+{
+	struct clk_fixup_div *fixup_div;
+	struct clk *clk;
+	struct clk_init_data init;
+
+	if (!fixup)
+		return ERR_PTR(-EINVAL);
+
+	fixup_div = kzalloc(sizeof(*fixup_div), GFP_KERNEL);
+	if (!fixup_div)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.ops = &clk_fixup_div_ops;
+	init.flags = CLK_SET_RATE_PARENT;
+	init.parent_names = parent ? &parent : NULL;
+	init.num_parents = parent ? 1 : 0;
+
+	fixup_div->divider.reg = reg;
+	fixup_div->divider.shift = shift;
+	fixup_div->divider.width = width;
+	fixup_div->divider.lock = &imx_ccm_lock;
+	fixup_div->divider.hw.init = &init;
+	fixup_div->ops = &clk_divider_ops;
+	fixup_div->fixup = fixup;
+
+	clk = clk_register(NULL, &fixup_div->divider.hw);
+	if (IS_ERR(clk))
+		kfree(fixup_div);
+
+	return clk;
+}

arch/arm/mach-imx/clk.h

@@ -49,6 +49,10 @@ struct clk *imx_clk_busy_mux(const char *name, void __iomem *reg, u8 shift,
 			     u8 width, void __iomem *busy_reg, u8 busy_shift,
 			     const char **parent_names, int num_parents);
 
+struct clk *imx_clk_fixup_divider(const char *name, const char *parent,
+				  void __iomem *reg, u8 shift, u8 width,
+				  void (*fixup)(u32 *val));
+
 static inline struct clk *imx_clk_fixed(const char *name, int rate)
 {
 	return clk_register_fixed_rate(NULL, name, NULL, CLK_IS_ROOT, rate);