clk: rockchip: add new clock-type for the cpuclk

When changing the armclk on Rockchip SoCs it is supposed to be reparented
to an alternate parent before changing the underlying pll and back after
the change. Additionally there exist clocks that are very tightly bound to
the armclk whose divider values are set according to the armclk rate.

Add a special clock-type to handle all that. The rate table and divider
values will be supplied from the soc-specific clock controllers.

Signed-off-by: Heiko Stuebner <[e-mail]>
Reviewed-by: Doug Anderson <[e-mail]>
On a rk3288-board:
Tested-by: Doug Anderson <[e-mail]>

drivers/clk/rockchip/Makefile

···
 obj-y	+= clk-rockchip.o
 obj-y	+= clk.o
 obj-y	+= clk-pll.o
+obj-y	+= clk-cpu.o
 obj-$(CONFIG_RESET_CONTROLLER)	+= softrst.o
 
 obj-y	+= clk-rk3188.o

drivers/clk/rockchip/clk-cpu.c

···
+/*
+ * Copyright (c) 2014 MundoReader S.L.
+ * Author: Heiko Stuebner <[e-mail]>
+ *
+ * based on clk/samsung/clk-cpu.c
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author: Thomas Abraham <[e-mail]>
+ *
+ * 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.
+ *
+ * A CPU clock is defined as a clock supplied to a CPU or a group of CPUs.
+ * The CPU clock is typically derived from a hierarchy of clock
+ * blocks which includes mux and divider blocks. There are a number of other
+ * auxiliary clocks supplied to the CPU domain such as the debug blocks and AXI
+ * clock for CPU domain. The rates of these auxiliary clocks are related to the
+ * CPU clock rate and this relation is usually specified in the hardware manual
+ * of the SoC or supplied after the SoC characterization.
+ *
+ * The below implementation of the CPU clock allows the rate changes of the CPU
+ * clock and the corresponding rate changes of the auxillary clocks of the CPU
+ * domain. The platform clock driver provides a clock register configuration
+ * for each configurable rate which is then used to program the clock hardware
+ * registers to acheive a fast co-oridinated rate change for all the CPU domain
+ * clocks.
+ *
+ * On a rate change request for the CPU clock, the rate change is propagated
+ * upto the PLL supplying the clock to the CPU domain clock blocks. While the
+ * CPU domain PLL is reconfigured, the CPU domain clocks are driven using an
+ * alternate clock source. If required, the alternate clock source is divided
+ * down in order to keep the output clock rate within the previous OPP limits.
+ */
+
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/clk-provider.h>
+#include "clk.h"
+
+/**
+ * struct rockchip_cpuclk: information about clock supplied to a CPU core.
+ * @hw:		handle between ccf and cpu clock.
+ * @alt_parent:	alternate parent clock to use when switching the speed
+ *		of the primary parent clock.
+ * @reg_base:	base register for cpu-clock values.
+ * @clk_nb:	clock notifier registered for changes in clock speed of the
+ *		primary parent clock.
+ * @rate_count:	number of rates in the rate_table
+ * @rate_table:	pll-rates and their associated dividers
+ * @reg_data:	cpu-specific register settings
+ * @lock:	clock lock
+ */
+struct rockchip_cpuclk {
+	struct clk_hw				hw;
+
+	struct clk_mux				cpu_mux;
+	const struct clk_ops			*cpu_mux_ops;
+
+	struct clk				*alt_parent;
+	void __iomem				*reg_base;
+	struct notifier_block			clk_nb;
+	unsigned int				rate_count;
+	struct rockchip_cpuclk_rate_table	*rate_table;
+	const struct rockchip_cpuclk_reg_data	*reg_data;
+	spinlock_t				*lock;
+};
+
+#define to_rockchip_cpuclk_hw(hw) container_of(hw, struct rockchip_cpuclk, hw)
+#define to_rockchip_cpuclk_nb(nb) \
+			container_of(nb, struct rockchip_cpuclk, clk_nb)
+
+static const struct rockchip_cpuclk_rate_table *rockchip_get_cpuclk_settings(
+			    struct rockchip_cpuclk *cpuclk, unsigned long rate)
+{
+	const struct rockchip_cpuclk_rate_table *rate_table =
+							cpuclk->rate_table;
+	int i;
+
+	for (i = 0; i < cpuclk->rate_count; i++) {
+		if (rate == rate_table[i].prate)
+			return &rate_table[i];
+	}
+
+	return NULL;
+}
+
+static unsigned long rockchip_cpuclk_recalc_rate(struct clk_hw *hw,
+					unsigned long parent_rate)
+{
+	struct rockchip_cpuclk *cpuclk = to_rockchip_cpuclk_hw(hw);
+	const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
+	u32 clksel0 = readl_relaxed(cpuclk->reg_base + reg_data->core_reg);
+
+	clksel0 >>= reg_data->div_core_shift;
+	clksel0 &= reg_data->div_core_mask;
+	return parent_rate / (clksel0 + 1);
+}
+
+static const struct clk_ops rockchip_cpuclk_ops = {
+	.recalc_rate = rockchip_cpuclk_recalc_rate,
+};
+
+static void rockchip_cpuclk_set_dividers(struct rockchip_cpuclk *cpuclk,
+				const struct rockchip_cpuclk_rate_table *rate)
+{
+	int i;
+
+	/* alternate parent is active now. set the dividers */
+	for (i = 0; i < ARRAY_SIZE(rate->divs); i++) {
+		const struct rockchip_cpuclk_clksel *clksel = &rate->divs[i];
+
+		if (!clksel->reg)
+			continue;
+
+		pr_debug("%s: setting reg 0x%x to 0x%x\n",
+			 __func__, clksel->reg, clksel->val);
+		writel(clksel->val , cpuclk->reg_base + clksel->reg);
+	}
+}
+
+static int rockchip_cpuclk_pre_rate_change(struct rockchip_cpuclk *cpuclk,
+					   struct clk_notifier_data *ndata)
+{
+	const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
+	unsigned long alt_prate, alt_div;
+
+	alt_prate = clk_get_rate(cpuclk->alt_parent);
+
+	spin_lock(cpuclk->lock);
+
+	/*
+	 * If the old parent clock speed is less than the clock speed
+	 * of the alternate parent, then it should be ensured that at no point
+	 * the armclk speed is more than the old_rate until the dividers are
+	 * set.
+	 */
+	if (alt_prate > ndata->old_rate) {
+		/* calculate dividers */
+		alt_div =  DIV_ROUND_UP(alt_prate, ndata->old_rate) - 1;
+		if (alt_div > reg_data->div_core_mask) {
+			pr_warn("%s: limiting alt-divider %lu to %d\n",
+				__func__, alt_div, reg_data->div_core_mask);
+			alt_div = reg_data->div_core_mask;
+		}
+
+		/*
+		 * Change parents and add dividers in a single transaction.
+		 *
+		 * NOTE: we do this in a single transaction so we're never
+		 * dividing the primary parent by the extra dividers that were
+		 * needed for the alt.
+		 */
+		pr_debug("%s: setting div %lu as alt-rate %lu > old-rate %lu\n",
+			 __func__, alt_div, alt_prate, ndata->old_rate);
+
+		writel(HIWORD_UPDATE(alt_div, reg_data->div_core_mask,
+					      reg_data->div_core_shift) |
+		       HIWORD_UPDATE(1, 1, reg_data->mux_core_shift),
+		       cpuclk->reg_base + reg_data->core_reg);
+	} else {
+		/* select alternate parent */
+		writel(HIWORD_UPDATE(1, 1, reg_data->mux_core_shift),
+			cpuclk->reg_base + reg_data->core_reg);
+	}
+
+	spin_unlock(cpuclk->lock);
+	return 0;
+}
+
+static int rockchip_cpuclk_post_rate_change(struct rockchip_cpuclk *cpuclk,
+					    struct clk_notifier_data *ndata)
+{
+	const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
+	const struct rockchip_cpuclk_rate_table *rate;
+
+	rate = rockchip_get_cpuclk_settings(cpuclk, ndata->new_rate);
+	if (!rate) {
+		pr_err("%s: Invalid rate : %lu for cpuclk\n",
+		       __func__, ndata->new_rate);
+		return -EINVAL;
+	}
+
+	spin_lock(cpuclk->lock);
+
+	if (ndata->old_rate < ndata->new_rate)
+		rockchip_cpuclk_set_dividers(cpuclk, rate);
+
+	/*
+	 * post-rate change event, re-mux to primary parent and remove dividers.
+	 *
+	 * NOTE: we do this in a single transaction so we're never dividing the
+	 * primary parent by the extra dividers that were needed for the alt.
+	 */
+
+	writel(HIWORD_UPDATE(0, reg_data->div_core_mask,
+				reg_data->div_core_shift) |
+	       HIWORD_UPDATE(0, 1, reg_data->mux_core_shift),
+	       cpuclk->reg_base + reg_data->core_reg);
+
+	if (ndata->old_rate > ndata->new_rate)
+		rockchip_cpuclk_set_dividers(cpuclk, rate);
+
+	spin_unlock(cpuclk->lock);
+	return 0;
+}
+
+/*
+ * This clock notifier is called when the frequency of the parent clock
+ * of cpuclk is to be changed. This notifier handles the setting up all
+ * the divider clocks, remux to temporary parent and handling the safe
+ * frequency levels when using temporary parent.
+ */
+static int rockchip_cpuclk_notifier_cb(struct notifier_block *nb,
+					unsigned long event, void *data)
+{
+	struct clk_notifier_data *ndata = data;
+	struct rockchip_cpuclk *cpuclk = to_rockchip_cpuclk_nb(nb);
+	int ret = 0;
+
+	pr_debug("%s: event %lu, old_rate %lu, new_rate: %lu\n",
+		 __func__, event, ndata->old_rate, ndata->new_rate);
+	if (event == PRE_RATE_CHANGE)
+		ret = rockchip_cpuclk_pre_rate_change(cpuclk, ndata);
+	else if (event == POST_RATE_CHANGE)
+		ret = rockchip_cpuclk_post_rate_change(cpuclk, ndata);
+
+	return notifier_from_errno(ret);
+}
+
+struct clk *rockchip_clk_register_cpuclk(const char *name,
+			const char **parent_names, u8 num_parents,
+			const struct rockchip_cpuclk_reg_data *reg_data,
+			const struct rockchip_cpuclk_rate_table *rates,
+			int nrates, void __iomem *reg_base, spinlock_t *lock)
+{
+	struct rockchip_cpuclk *cpuclk;
+	struct clk_init_data init;
+	struct clk *clk, *cclk;
+	int ret;
+
+	if (num_parents != 2) {
+		pr_err("%s: needs two parent clocks\n", __func__);
+		return ERR_PTR(-EINVAL);
+	}
+
+	cpuclk = kzalloc(sizeof(*cpuclk), GFP_KERNEL);
+	if (!cpuclk)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.parent_names = &parent_names[0];
+	init.num_parents = 1;
+	init.ops = &rockchip_cpuclk_ops;
+
+	/* only allow rate changes when we have a rate table */
+	init.flags = (nrates > 0) ? CLK_SET_RATE_PARENT : 0;
+
+	/* disallow automatic parent changes by ccf */
+	init.flags |= CLK_SET_RATE_NO_REPARENT;
+
+	init.flags |= CLK_GET_RATE_NOCACHE;
+
+	cpuclk->reg_base = reg_base;
+	cpuclk->lock = lock;
+	cpuclk->reg_data = reg_data;
+	cpuclk->clk_nb.notifier_call = rockchip_cpuclk_notifier_cb;
+	cpuclk->hw.init = &init;
+
+	cpuclk->alt_parent = __clk_lookup(parent_names[1]);
+	if (!cpuclk->alt_parent) {
+		pr_err("%s: could not lookup alternate parent\n",
+		       __func__);
+		ret = -EINVAL;
+		goto free_cpuclk;
+	}
+
+	ret = clk_prepare_enable(cpuclk->alt_parent);
+	if (ret) {
+		pr_err("%s: could not enable alternate parent\n",
+		       __func__);
+		goto free_cpuclk;
+	}
+
+	clk = __clk_lookup(parent_names[0]);
+	if (!clk) {
+		pr_err("%s: could not lookup parent clock %s\n",
+		       __func__, parent_names[0]);
+		ret = -EINVAL;
+		goto free_cpuclk;
+	}
+
+	ret = clk_notifier_register(clk, &cpuclk->clk_nb);
+	if (ret) {
+		pr_err("%s: failed to register clock notifier for %s\n",
+				__func__, name);
+		goto free_cpuclk;
+	}
+
+	if (nrates > 0) {
+		cpuclk->rate_count = nrates;
+		cpuclk->rate_table = kmemdup(rates,
+					     sizeof(*rates) * nrates,
+					     GFP_KERNEL);
+		if (!cpuclk->rate_table) {
+			pr_err("%s: could not allocate memory for cpuclk rates\n",
+			       __func__);
+			ret = -ENOMEM;
+			goto unregister_notifier;
+		}
+	}
+
+	cclk = clk_register(NULL, &cpuclk->hw);
+	if (IS_ERR(clk)) {
+		pr_err("%s: could not register cpuclk %s\n", __func__,	name);
+		ret = PTR_ERR(clk);
+		goto free_rate_table;
+	}
+
+	return cclk;
+
+free_rate_table:
+	kfree(cpuclk->rate_table);
+unregister_notifier:
+	clk_notifier_unregister(clk, &cpuclk->clk_nb);
+free_cpuclk:
+	kfree(cpuclk);
+	return ERR_PTR(ret);
+}

drivers/clk/rockchip/clk.c

···
 	}
 }
 
+void __init rockchip_clk_register_armclk(unsigned int lookup_id,
+			const char *name, const char **parent_names,
+			u8 num_parents,
+			const struct rockchip_cpuclk_reg_data *reg_data,
+			const struct rockchip_cpuclk_rate_table *rates,
+			int nrates)
+{
+	struct clk *clk;
+
+	clk = rockchip_clk_register_cpuclk(name, parent_names, num_parents,
+					   reg_data, rates, nrates, reg_base,
+					   &clk_lock);
+	if (IS_ERR(clk)) {
+		pr_err("%s: failed to register clock %s: %ld\n",
+		       __func__, name, PTR_ERR(clk));
+		return;
+	}
+
+	rockchip_clk_add_lookup(clk, lookup_id);
+}
+
 void __init rockchip_clk_protect_critical(const char *clocks[], int nclocks)
 {
 	int i;

drivers/clk/rockchip/clk.h

···
 		struct rockchip_pll_rate_table *rate_table,
 		spinlock_t *lock);
 
+struct rockchip_cpuclk_clksel {
+	int reg;
+	u32 val;
+};
+
+#define ROCKCHIP_CPUCLK_NUM_DIVIDERS	2
+struct rockchip_cpuclk_rate_table {
+	unsigned long prate;
+	struct rockchip_cpuclk_clksel divs[ROCKCHIP_CPUCLK_NUM_DIVIDERS];
+};
+
+/**
+ * struct rockchip_cpuclk_reg_data: describes register offsets and masks of the cpuclock
+ * @core_reg:		register offset of the core settings register
+ * @div_core_shift:	core divider offset used to divide the pll value
+ * @div_core_mask:	core divider mask
+ * @mux_core_shift:	offset of the core multiplexer
+ */
+struct rockchip_cpuclk_reg_data {
+	int		core_reg;
+	u8		div_core_shift;
+	u32		div_core_mask;
+	int		mux_core_reg;
+	u8		mux_core_shift;
+};
+
+struct clk *rockchip_clk_register_cpuclk(const char *name,
+			const char **parent_names, u8 num_parents,
+			const struct rockchip_cpuclk_reg_data *reg_data,
+			const struct rockchip_cpuclk_rate_table *rates,
+			int nrates, void __iomem *reg_base, spinlock_t *lock);
+
 #define PNAME(x) static const char *x[] __initconst
 
 enum rockchip_clk_branch_type {
···
 				    unsigned int nr_clk);
 void rockchip_clk_register_plls(struct rockchip_pll_clock *pll_list,
 				unsigned int nr_pll, int grf_lock_offset);
+void rockchip_clk_register_armclk(unsigned int lookup_id, const char *name,
+			const char **parent_names, u8 num_parents,
+			const struct rockchip_cpuclk_reg_data *reg_data,
+			const struct rockchip_cpuclk_rate_table *rates,
+			int nrates);
 void rockchip_clk_protect_critical(const char *clocks[], int nclocks);
 
 #define ROCKCHIP_SOFTRST_HIWORD_MASK	BIT(0)