clk: st: STiH407: Support for Flexgen Clocks

This patch is the Flexgen implementation reusing as much as possible
of Common Clock Framework functions.

The idea is to have an instance of "struct flexgen" per output clock.
It represents the clock cross bar (by a mux element), and the pre and final dividers
(using dividers and gates elements).
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: Olivier Bideau <olivier.bideau@st.com>
Signed-off-by: Gabriel Fernandez <gabriel.fernandez@linaro.org>
Acked-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/st/Makefile

-obj-y += clkgen-mux.o clkgen-pll.o clkgen-fsyn.o
+obj-y += clkgen-mux.o clkgen-pll.o clkgen-fsyn.o clk-flexgen.o

drivers/clk/st/clk-flexgen.c

+/*
+ * clk-flexgen.c
+ *
+ * Copyright (C) ST-Microelectronics SA 2013
+ * Author:  Maxime Coquelin <maxime.coquelin@st.com> for ST-Microelectronics.
+ * License terms:  GNU General Public License (GPL), version 2  */
+
+#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>
+#include <linux/of.h>
+#include <linux/of_address.h>
+
+struct flexgen {
+	struct clk_hw hw;
+
+	/* Crossbar */
+	struct clk_mux mux;
+	/* Pre-divisor's gate */
+	struct clk_gate pgate;
+	/* Pre-divisor */
+	struct clk_divider pdiv;
+	/* Final divisor's gate */
+	struct clk_gate fgate;
+	/* Final divisor */
+	struct clk_divider fdiv;
+};
+
+#define to_flexgen(_hw) container_of(_hw, struct flexgen, hw)
+
+static int flexgen_enable(struct clk_hw *hw)
+{
+	struct flexgen *flexgen = to_flexgen(hw);
+	struct clk_hw *pgate_hw = &flexgen->pgate.hw;
+	struct clk_hw *fgate_hw = &flexgen->fgate.hw;
+
+	pgate_hw->clk = hw->clk;
+	fgate_hw->clk = hw->clk;
+
+	clk_gate_ops.enable(pgate_hw);
+
+	clk_gate_ops.enable(fgate_hw);
+
+	pr_debug("%s: flexgen output enabled\n", __clk_get_name(hw->clk));
+	return 0;
+}
+
+static void flexgen_disable(struct clk_hw *hw)
+{
+	struct flexgen *flexgen = to_flexgen(hw);
+	struct clk_hw *fgate_hw = &flexgen->fgate.hw;
+
+	/* disable only the final gate */
+	fgate_hw->clk = hw->clk;
+
+	clk_gate_ops.disable(fgate_hw);
+
+	pr_debug("%s: flexgen output disabled\n", __clk_get_name(hw->clk));
+}
+
+static int flexgen_is_enabled(struct clk_hw *hw)
+{
+	struct flexgen *flexgen = to_flexgen(hw);
+	struct clk_hw *fgate_hw = &flexgen->fgate.hw;
+
+	fgate_hw->clk = hw->clk;
+
+	if (!clk_gate_ops.is_enabled(fgate_hw))
+		return 0;
+
+	return 1;
+}
+
+static u8 flexgen_get_parent(struct clk_hw *hw)
+{
+	struct flexgen *flexgen = to_flexgen(hw);
+	struct clk_hw *mux_hw = &flexgen->mux.hw;
+
+	mux_hw->clk = hw->clk;
+
+	return clk_mux_ops.get_parent(mux_hw);
+}
+
+static int flexgen_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct flexgen *flexgen = to_flexgen(hw);
+	struct clk_hw *mux_hw = &flexgen->mux.hw;
+
+	mux_hw->clk = hw->clk;
+
+	return clk_mux_ops.set_parent(mux_hw, index);
+}
+
+static inline unsigned long
+clk_best_div(unsigned long parent_rate, unsigned long rate)
+{
+	return parent_rate / rate + ((rate > (2*(parent_rate % rate))) ? 0 : 1);
+}
+
+static long flexgen_round_rate(struct clk_hw *hw, unsigned long rate,
+				   unsigned long *prate)
+{
+	unsigned long div;
+
+	/* Round div according to exact prate and wished rate */
+	div = clk_best_div(*prate, rate);
+
+	if (__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT) {
+		*prate = rate * div;
+		return rate;
+	}
+
+	return *prate / div;
+}
+
+unsigned long flexgen_recalc_rate(struct clk_hw *hw,
+		unsigned long parent_rate)
+{
+	struct flexgen *flexgen = to_flexgen(hw);
+	struct clk_hw *pdiv_hw = &flexgen->pdiv.hw;
+	struct clk_hw *fdiv_hw = &flexgen->fdiv.hw;
+	unsigned long mid_rate;
+
+	pdiv_hw->clk = hw->clk;
+	fdiv_hw->clk = hw->clk;
+
+	mid_rate = clk_divider_ops.recalc_rate(pdiv_hw, parent_rate);
+
+	return clk_divider_ops.recalc_rate(fdiv_hw, mid_rate);
+}
+
+static int flexgen_set_rate(struct clk_hw *hw, unsigned long rate,
+				unsigned long parent_rate)
+{
+	struct flexgen *flexgen = to_flexgen(hw);
+	struct clk_hw *pdiv_hw = &flexgen->pdiv.hw;
+	struct clk_hw *fdiv_hw = &flexgen->fdiv.hw;
+	unsigned long primary_div = 0;
+	int ret = 0;
+
+	pdiv_hw->clk = hw->clk;
+	fdiv_hw->clk = hw->clk;
+
+	primary_div = clk_best_div(parent_rate, rate);
+
+	clk_divider_ops.set_rate(fdiv_hw, parent_rate, parent_rate);
+	ret = clk_divider_ops.set_rate(pdiv_hw, rate, rate * primary_div);
+
+	return ret;
+}
+
+static const struct clk_ops flexgen_ops = {
+	.enable = flexgen_enable,
+	.disable = flexgen_disable,
+	.is_enabled = flexgen_is_enabled,
+	.get_parent = flexgen_get_parent,
+	.set_parent = flexgen_set_parent,
+	.round_rate = flexgen_round_rate,
+	.recalc_rate = flexgen_recalc_rate,
+	.set_rate = flexgen_set_rate,
+};
+
+struct clk *clk_register_flexgen(const char *name,
+				const char **parent_names, u8 num_parents,
+				void __iomem *reg, spinlock_t *lock, u32 idx,
+				unsigned long flexgen_flags) {
+	struct flexgen *fgxbar;
+	struct clk *clk;
+	struct clk_init_data init;
+	u32  xbar_shift;
+	void __iomem *xbar_reg, *fdiv_reg;
+
+	fgxbar = kzalloc(sizeof(struct flexgen), GFP_KERNEL);
+	if (!fgxbar)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.ops = &flexgen_ops;
+	init.flags = CLK_IS_BASIC | flexgen_flags;
+	init.parent_names = parent_names;
+	init.num_parents = num_parents;
+
+	xbar_reg = reg + 0x18 + (idx & ~0x3);
+	xbar_shift = (idx % 4) * 0x8;
+	fdiv_reg = reg + 0x164 + idx * 4;
+
+	/* Crossbar element config */
+	fgxbar->mux.lock = lock;
+	fgxbar->mux.mask = BIT(6) - 1;
+	fgxbar->mux.reg = xbar_reg;
+	fgxbar->mux.shift = xbar_shift;
+	fgxbar->mux.table = NULL;
+
+
+	/* Pre-divider's gate config (in xbar register)*/
+	fgxbar->pgate.lock = lock;
+	fgxbar->pgate.reg = xbar_reg;
+	fgxbar->pgate.bit_idx = xbar_shift + 6;
+
+	/* Pre-divider config */
+	fgxbar->pdiv.lock = lock;
+	fgxbar->pdiv.reg = reg + 0x58 + idx * 4;
+	fgxbar->pdiv.width = 10;
+
+	/* Final divider's gate config */
+	fgxbar->fgate.lock = lock;
+	fgxbar->fgate.reg = fdiv_reg;
+	fgxbar->fgate.bit_idx = 6;
+
+	/* Final divider config */
+	fgxbar->fdiv.lock = lock;
+	fgxbar->fdiv.reg = fdiv_reg;
+	fgxbar->fdiv.width = 6;
+
+	fgxbar->hw.init = &init;
+
+	clk = clk_register(NULL, &fgxbar->hw);
+	if (IS_ERR(clk))
+		kfree(fgxbar);
+	else
+		pr_debug("%s: parent %s rate %u\n",
+			__clk_get_name(clk),
+			__clk_get_name(clk_get_parent(clk)),
+			(unsigned int)clk_get_rate(clk));
+	return clk;
+}
+
+static const char ** __init flexgen_get_parents(struct device_node *np,
+						       int *num_parents)
+{
+	const char **parents;
+	int nparents, i;
+
+	nparents = of_count_phandle_with_args(np, "clocks", "#clock-cells");
+	if (WARN_ON(nparents <= 0))
+		return NULL;
+
+	parents = kcalloc(nparents, sizeof(const char *), GFP_KERNEL);
+	if (!parents)
+		return NULL;
+
+	for (i = 0; i < nparents; i++)
+		parents[i] = of_clk_get_parent_name(np, i);
+
+	*num_parents = nparents;
+	return parents;
+}
+
+void __init st_of_flexgen_setup(struct device_node *np)
+{
+	struct device_node *pnode;
+	void __iomem *reg;
+	struct clk_onecell_data *clk_data;
+	const char **parents;
+	int num_parents, i;
+	spinlock_t *rlock = NULL;
+	unsigned long flex_flags = 0;
+
+	pnode = of_get_parent(np);
+	if (!pnode)
+		return;
+
+	reg = of_iomap(pnode, 0);
+	if (!reg)
+		return;
+
+	parents = flexgen_get_parents(np, &num_parents);
+	if (!parents)
+		return;
+
+	clk_data = kzalloc(sizeof(*clk_data), GFP_KERNEL);
+	if (!clk_data)
+		goto err;
+
+	clk_data->clk_num = of_property_count_strings(np ,
+			"clock-output-names");
+	if (clk_data->clk_num <= 0) {
+		pr_err("%s: Failed to get number of output clocks (%d)",
+				__func__, clk_data->clk_num);
+		goto err;
+	}
+
+	clk_data->clks = kcalloc(clk_data->clk_num, sizeof(struct clk *),
+			GFP_KERNEL);
+	if (!clk_data->clks)
+		goto err;
+
+	rlock = kzalloc(sizeof(spinlock_t), GFP_KERNEL);
+	if (!rlock)
+		goto err;
+
+	for (i = 0; i < clk_data->clk_num; i++) {
+		struct clk *clk;
+		const char *clk_name;
+
+		if (of_property_read_string_index(np, "clock-output-names",
+						  i, &clk_name)) {
+			break;
+		}
+
+		/*
+		 * If we read an empty clock name then the output is unused
+		 */
+		if (*clk_name == '\0')
+			continue;
+
+		clk = clk_register_flexgen(clk_name, parents, num_parents,
+					   reg, rlock, i, flex_flags);
+
+		if (IS_ERR(clk))
+			goto err;
+
+		clk_data->clks[i] = clk;
+	}
+
+	kfree(parents);
+	of_clk_add_provider(np, of_clk_src_onecell_get, clk_data);
+
+	return;
+
+err:
+	if (clk_data)
+		kfree(clk_data->clks);
+	kfree(clk_data);
+	kfree(parents);
+	kfree(rlock);
+}
+CLK_OF_DECLARE(flexgen, "st,flexgen", st_of_flexgen_setup);