clk: add lpc18xx creg clk driver

The CREG block on lpc18xx contains configuration register
for two low power clocks. Support enabling of these two
clocks with a clk driver that access CREG trough the
syscon regmap interface.

These clocks are needed to support peripherals like the
internal RTC on lpc18xx.
Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/nxp/Makefile

 obj-$(CONFIG_ARCH_LPC18XX)	+= clk-lpc18xx-cgu.o
 obj-$(CONFIG_ARCH_LPC18XX)	+= clk-lpc18xx-ccu.o
+obj-$(CONFIG_ARCH_LPC18XX)	+= clk-lpc18xx-creg.o
 obj-$(CONFIG_ARCH_LPC32XX)	+= clk-lpc32xx.o

drivers/clk/nxp/clk-lpc18xx-creg.c

+/*
+ * Clk driver for NXP LPC18xx/43xx Configuration Registers (CREG)
+ *
+ * Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define LPC18XX_CREG_CREG0			0x004
+#define  LPC18XX_CREG_CREG0_EN1KHZ		BIT(0)
+#define  LPC18XX_CREG_CREG0_EN32KHZ		BIT(1)
+#define  LPC18XX_CREG_CREG0_RESET32KHZ		BIT(2)
+#define  LPC18XX_CREG_CREG0_PD32KHZ		BIT(3)
+
+#define to_clk_creg(_hw) container_of(_hw, struct clk_creg_data, hw)
+
+enum {
+	CREG_CLK_1KHZ,
+	CREG_CLK_32KHZ,
+	CREG_CLK_MAX,
+};
+
+struct clk_creg_data {
+	struct clk_hw hw;
+	const char *name;
+	struct regmap *reg;
+	unsigned int en_mask;
+	const struct clk_ops *ops;
+};
+
+#define CREG_CLK(_name, _emask, _ops)		\
+{						\
+	.name = _name,				\
+	.en_mask = LPC18XX_CREG_CREG0_##_emask,	\
+	.ops = &_ops,				\
+}
+
+static int clk_creg_32k_prepare(struct clk_hw *hw)
+{
+	struct clk_creg_data *creg = to_clk_creg(hw);
+	int ret;
+
+	ret = regmap_update_bits(creg->reg, LPC18XX_CREG_CREG0,
+				 LPC18XX_CREG_CREG0_PD32KHZ |
+				 LPC18XX_CREG_CREG0_RESET32KHZ, 0);
+
+	/*
+	 * Powering up the 32k oscillator takes a long while
+	 * and sadly there aren't any status bit to poll.
+	 */
+	msleep(2500);
+
+	return ret;
+}
+
+static void clk_creg_32k_unprepare(struct clk_hw *hw)
+{
+	struct clk_creg_data *creg = to_clk_creg(hw);
+
+	regmap_update_bits(creg->reg, LPC18XX_CREG_CREG0,
+			   LPC18XX_CREG_CREG0_PD32KHZ,
+			   LPC18XX_CREG_CREG0_PD32KHZ);
+}
+
+static int clk_creg_32k_is_prepared(struct clk_hw *hw)
+{
+	struct clk_creg_data *creg = to_clk_creg(hw);
+	u32 reg;
+
+	regmap_read(creg->reg, LPC18XX_CREG_CREG0, &reg);
+
+	return !(reg & LPC18XX_CREG_CREG0_PD32KHZ) &&
+	       !(reg & LPC18XX_CREG_CREG0_RESET32KHZ);
+}
+
+static unsigned long clk_creg_1k_recalc_rate(struct clk_hw *hw,
+					     unsigned long parent_rate)
+{
+	return parent_rate / 32;
+}
+
+static int clk_creg_enable(struct clk_hw *hw)
+{
+	struct clk_creg_data *creg = to_clk_creg(hw);
+
+	return regmap_update_bits(creg->reg, LPC18XX_CREG_CREG0,
+				  creg->en_mask, creg->en_mask);
+}
+
+static void clk_creg_disable(struct clk_hw *hw)
+{
+	struct clk_creg_data *creg = to_clk_creg(hw);
+
+	regmap_update_bits(creg->reg, LPC18XX_CREG_CREG0,
+			   creg->en_mask, 0);
+}
+
+static int clk_creg_is_enabled(struct clk_hw *hw)
+{
+	struct clk_creg_data *creg = to_clk_creg(hw);
+	u32 reg;
+
+	regmap_read(creg->reg, LPC18XX_CREG_CREG0, &reg);
+
+	return !!(reg & creg->en_mask);
+}
+
+static const struct clk_ops clk_creg_32k = {
+	.enable		= clk_creg_enable,
+	.disable	= clk_creg_disable,
+	.is_enabled	= clk_creg_is_enabled,
+	.prepare	= clk_creg_32k_prepare,
+	.unprepare	= clk_creg_32k_unprepare,
+	.is_prepared	= clk_creg_32k_is_prepared,
+};
+
+static const struct clk_ops clk_creg_1k = {
+	.enable		= clk_creg_enable,
+	.disable	= clk_creg_disable,
+	.is_enabled	= clk_creg_is_enabled,
+	.recalc_rate	= clk_creg_1k_recalc_rate,
+};
+
+static struct clk_creg_data clk_creg_clocks[] = {
+	[CREG_CLK_1KHZ]  = CREG_CLK("1khz_clk",  EN1KHZ,  clk_creg_1k),
+	[CREG_CLK_32KHZ] = CREG_CLK("32khz_clk", EN32KHZ, clk_creg_32k),
+};
+
+static struct clk *clk_register_creg_clk(struct device *dev,
+					 struct clk_creg_data *creg_clk,
+					 const char **parent_name,
+					 struct regmap *syscon)
+{
+	struct clk_init_data init;
+
+	init.ops = creg_clk->ops;
+	init.name = creg_clk->name;
+	init.parent_names = parent_name;
+	init.num_parents = 1;
+
+	creg_clk->reg = syscon;
+	creg_clk->hw.init = &init;
+
+	if (dev)
+		return devm_clk_register(dev, &creg_clk->hw);
+
+	return clk_register(NULL, &creg_clk->hw);
+}
+
+static struct clk *clk_creg_early[CREG_CLK_MAX];
+static struct clk_onecell_data clk_creg_early_data = {
+	.clks = clk_creg_early,
+	.clk_num = CREG_CLK_MAX,
+};
+
+static void __init lpc18xx_creg_clk_init(struct device_node *np)
+{
+	const char *clk_32khz_parent;
+	struct regmap *syscon;
+
+	syscon = syscon_node_to_regmap(np->parent);
+	if (IS_ERR(syscon)) {
+		pr_err("%s: syscon lookup failed\n", __func__);
+		return;
+	}
+
+	clk_32khz_parent = of_clk_get_parent_name(np, 0);
+
+	clk_creg_early[CREG_CLK_32KHZ] =
+		clk_register_creg_clk(NULL, &clk_creg_clocks[CREG_CLK_32KHZ],
+				      &clk_32khz_parent, syscon);
+	clk_creg_early[CREG_CLK_1KHZ] = ERR_PTR(-EPROBE_DEFER);
+
+	of_clk_add_provider(np, of_clk_src_onecell_get, &clk_creg_early_data);
+}
+CLK_OF_DECLARE(lpc18xx_creg_clk, "nxp,lpc1850-creg-clk", lpc18xx_creg_clk_init);
+
+static struct clk *clk_creg[CREG_CLK_MAX];
+static struct clk_onecell_data clk_creg_data = {
+	.clks = clk_creg,
+	.clk_num = CREG_CLK_MAX,
+};
+
+static int lpc18xx_creg_clk_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct regmap *syscon;
+
+	syscon = syscon_node_to_regmap(np->parent);
+	if (IS_ERR(syscon)) {
+		dev_err(&pdev->dev, "syscon lookup failed\n");
+		return PTR_ERR(syscon);
+	}
+
+	clk_creg[CREG_CLK_32KHZ] = clk_creg_early[CREG_CLK_32KHZ];
+	clk_creg[CREG_CLK_1KHZ] =
+		clk_register_creg_clk(NULL, &clk_creg_clocks[CREG_CLK_1KHZ],
+				      &clk_creg_clocks[CREG_CLK_32KHZ].name,
+				      syscon);
+
+	return of_clk_add_provider(np, of_clk_src_onecell_get, &clk_creg_data);
+}
+
+static const struct of_device_id lpc18xx_creg_clk_of_match[] = {
+	{ .compatible = "nxp,lpc1850-creg-clk" },
+	{},
+};
+
+static struct platform_driver lpc18xx_creg_clk_driver = {
+	.probe = lpc18xx_creg_clk_probe,
+	.driver = {
+		.name = "lpc18xx-creg-clk",
+		.of_match_table = lpc18xx_creg_clk_of_match,
+	},
+};
+builtin_platform_driver(lpc18xx_creg_clk_driver);