clk: samsung: add infrastructure to register cpu clocks

The CPU clock provider supplies the clock to the CPU clock domain. The
composition and organization of the CPU clock provider could vary among
Exynos SoCs. A CPU clock provider can be composed of clock mux, dividers
and gates. This patch defines a new clock type for CPU clock provider and
adds infrastructure to register the CPU clock providers for Samsung
platforms.

Changes by Bartlomiej:
- fixed issue with setting lower dividers before the parent clock speed
  was lowered (the issue resulted in lockup on Exynos4210 SoC based
  Origen board when "ondemand" cpufreq governor was stress tested)
- fixed missing spin_unlock on error in exynos_cpuclk_post_rate_change()
  problem by moving cfg_data search outside of the spin locked area
- removed leftover kfree() in exynos_register_cpu_clock() that could
  result in dereferencing the NULL pointer on error
- moved spin_lock earlier in exynos_cpuclk_pre_rate_change() to cover
  reading of E4210_SRC_CPU and E4210_DIV_CPU1 registers
- added missing "last chance" checks to wait_until_divider_stable() and
  wait_until_mux_stable() (needed in case that IRQ handling took long
  time to proceed and resulted in function printing incorrect error
  message about timeout)
- moved E4210_CPU_DIV[0,1]() macros just before their only users,
  this resulted in moving them from patch #2 to patch #3/6 ("clk:
  samsung: exynos4: add cpu clock configuration data and instantiate
  cpu clock")
- removed E5250_CPU_DIV[0,1](), E5420_EGL_DIV0() and E5420_KFC_DIV()
  macros for now
- added my Copyrights to drivers/clk/samsung/clk-cpu.c

Cc: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>

drivers/clk/samsung/Makefile

@@ -2,7 +2,7 @@
 # Samsung Clock specific Makefile
 #
 
-obj-$(CONFIG_COMMON_CLK)	+= clk.o clk-pll.o
+obj-$(CONFIG_COMMON_CLK)	+= clk.o clk-pll.o clk-cpu.o
 obj-$(CONFIG_SOC_EXYNOS3250)	+= clk-exynos3250.o
 obj-$(CONFIG_ARCH_EXYNOS4)	+= clk-exynos4.o
 obj-$(CONFIG_SOC_EXYNOS4415)	+= clk-exynos4415.o

drivers/clk/samsung/clk-cpu.c

@@ -0,0 +1,349 @@
+/*
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author: Thomas Abraham <thomas.ab@samsung.com>
+ *
+ * Copyright (c) 2015 Samsung Electronics Co., Ltd.
+ * Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
+ *
+ * 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.
+ *
+ * This file contains the utility function to register CPU clock for Samsung
+ * Exynos platforms. 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/errno.h>
+#include "clk-cpu.h"
+
+#define E4210_SRC_CPU		0x0
+#define E4210_STAT_CPU		0x200
+#define E4210_DIV_CPU0		0x300
+#define E4210_DIV_CPU1		0x304
+#define E4210_DIV_STAT_CPU0	0x400
+#define E4210_DIV_STAT_CPU1	0x404
+
+#define E4210_DIV0_RATIO0_MASK	0x7
+#define E4210_DIV1_HPM_MASK	(0x7 << 4)
+#define E4210_DIV1_COPY_MASK	(0x7 << 0)
+#define E4210_MUX_HPM_MASK	(1 << 20)
+#define E4210_DIV0_ATB_SHIFT	16
+#define E4210_DIV0_ATB_MASK	(DIV_MASK << E4210_DIV0_ATB_SHIFT)
+
+#define MAX_DIV			8
+#define DIV_MASK		7
+#define DIV_MASK_ALL		0xffffffff
+#define MUX_MASK		7
+
+/*
+ * Helper function to wait until divider(s) have stabilized after the divider
+ * value has changed.
+ */
+static void wait_until_divider_stable(void __iomem *div_reg, unsigned long mask)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(10);
+
+	do {
+		if (!(readl(div_reg) & mask))
+			return;
+	} while (time_before(jiffies, timeout));
+
+	if (!(readl(div_reg) & mask))
+		return;
+
+	pr_err("%s: timeout in divider stablization\n", __func__);
+}
+
+/*
+ * Helper function to wait until mux has stabilized after the mux selection
+ * value was changed.
+ */
+static void wait_until_mux_stable(void __iomem *mux_reg, u32 mux_pos,
+					unsigned long mux_value)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(10);
+
+	do {
+		if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
+			return;
+	} while (time_before(jiffies, timeout));
+
+	if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
+		return;
+
+	pr_err("%s: re-parenting mux timed-out\n", __func__);
+}
+
+/* common round rate callback useable for all types of CPU clocks */
+static long exynos_cpuclk_round_rate(struct clk_hw *hw,
+			unsigned long drate, unsigned long *prate)
+{
+	struct clk *parent = __clk_get_parent(hw->clk);
+	*prate = __clk_round_rate(parent, drate);
+	return *prate;
+}
+
+/* common recalc rate callback useable for all types of CPU clocks */
+static unsigned long exynos_cpuclk_recalc_rate(struct clk_hw *hw,
+			unsigned long parent_rate)
+{
+	/*
+	 * The CPU clock output (armclk) rate is the same as its parent
+	 * rate. Although there exist certain dividers inside the CPU
+	 * clock block that could be used to divide the parent clock,
+	 * the driver does not make use of them currently, except during
+	 * frequency transitions.
+	 */
+	return parent_rate;
+}
+
+static const struct clk_ops exynos_cpuclk_clk_ops = {
+	.recalc_rate = exynos_cpuclk_recalc_rate,
+	.round_rate = exynos_cpuclk_round_rate,
+};
+
+/*
+ * Helper function to set the 'safe' dividers for the CPU clock. The parameters
+ * div and mask contain the divider value and the register bit mask of the
+ * dividers to be programmed.
+ */
+static void exynos_set_safe_div(void __iomem *base, unsigned long div,
+					unsigned long mask)
+{
+	unsigned long div0;
+
+	div0 = readl(base + E4210_DIV_CPU0);
+	div0 = (div0 & ~mask) | (div & mask);
+	writel(div0, base + E4210_DIV_CPU0);
+	wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, mask);
+}
+
+/* handler for pre-rate change notification from parent clock */
+static int exynos_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
+			struct exynos_cpuclk *cpuclk, void __iomem *base)
+{
+	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
+	unsigned long alt_prate = clk_get_rate(cpuclk->alt_parent);
+	unsigned long alt_div = 0, alt_div_mask = DIV_MASK;
+	unsigned long div0, div1 = 0, mux_reg;
+
+	/* find out the divider values to use for clock data */
+	while ((cfg_data->prate * 1000) != ndata->new_rate) {
+		if (cfg_data->prate == 0)
+			return -EINVAL;
+		cfg_data++;
+	}
+
+	spin_lock(cpuclk->lock);
+
+	/*
+	 * For the selected PLL clock frequency, get the pre-defined divider
+	 * values. If the clock for sclk_hpm is not sourced from apll, then
+	 * the values for DIV_COPY and DIV_HPM dividers need not be set.
+	 */
+	div0 = cfg_data->div0;
+	if (test_bit(CLK_CPU_HAS_DIV1, &cpuclk->flags)) {
+		div1 = cfg_data->div1;
+		if (readl(base + E4210_SRC_CPU) & E4210_MUX_HPM_MASK)
+			div1 = readl(base + E4210_DIV_CPU1) &
+				(E4210_DIV1_HPM_MASK | E4210_DIV1_COPY_MASK);
+	}
+
+	/*
+	 * 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_prate until the dividers are
+	 * set.  Also workaround the issue of the dividers being set to lower
+	 * values before the parent clock speed is set to new lower speed
+	 * (this can result in too high speed of armclk output clocks).
+	 */
+	if (alt_prate > ndata->old_rate || ndata->old_rate > ndata->new_rate) {
+		unsigned long tmp_rate = min(ndata->old_rate, ndata->new_rate);
+
+		alt_div = DIV_ROUND_UP(alt_prate, tmp_rate) - 1;
+		WARN_ON(alt_div >= MAX_DIV);
+
+		if (test_bit(CLK_CPU_NEEDS_DEBUG_ALT_DIV, &cpuclk->flags)) {
+			/*
+			 * In Exynos4210, ATB clock parent is also mout_core. So
+			 * ATB clock also needs to be mantained at safe speed.
+			 */
+			alt_div |= E4210_DIV0_ATB_MASK;
+			alt_div_mask |= E4210_DIV0_ATB_MASK;
+		}
+		exynos_set_safe_div(base, alt_div, alt_div_mask);
+		div0 |= alt_div;
+	}
+
+	/* select sclk_mpll as the alternate parent */
+	mux_reg = readl(base + E4210_SRC_CPU);
+	writel(mux_reg | (1 << 16), base + E4210_SRC_CPU);
+	wait_until_mux_stable(base + E4210_STAT_CPU, 16, 2);
+
+	/* alternate parent is active now. set the dividers */
+	writel(div0, base + E4210_DIV_CPU0);
+	wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, DIV_MASK_ALL);
+
+	if (test_bit(CLK_CPU_HAS_DIV1, &cpuclk->flags)) {
+		writel(div1, base + E4210_DIV_CPU1);
+		wait_until_divider_stable(base + E4210_DIV_STAT_CPU1,
+				DIV_MASK_ALL);
+	}
+
+	spin_unlock(cpuclk->lock);
+	return 0;
+}
+
+/* handler for post-rate change notification from parent clock */
+static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
+			struct exynos_cpuclk *cpuclk, void __iomem *base)
+{
+	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
+	unsigned long div = 0, div_mask = DIV_MASK;
+	unsigned long mux_reg;
+
+	/* find out the divider values to use for clock data */
+	if (test_bit(CLK_CPU_NEEDS_DEBUG_ALT_DIV, &cpuclk->flags)) {
+		while ((cfg_data->prate * 1000) != ndata->new_rate) {
+			if (cfg_data->prate == 0)
+				return -EINVAL;
+			cfg_data++;
+		}
+	}
+
+	spin_lock(cpuclk->lock);
+
+	/* select mout_apll as the alternate parent */
+	mux_reg = readl(base + E4210_SRC_CPU);
+	writel(mux_reg & ~(1 << 16), base + E4210_SRC_CPU);
+	wait_until_mux_stable(base + E4210_STAT_CPU, 16, 1);
+
+	if (test_bit(CLK_CPU_NEEDS_DEBUG_ALT_DIV, &cpuclk->flags)) {
+		div |= (cfg_data->div0 & E4210_DIV0_ATB_MASK);
+		div_mask |= E4210_DIV0_ATB_MASK;
+	}
+
+	exynos_set_safe_div(base, div, div_mask);
+	spin_unlock(cpuclk->lock);
+	return 0;
+}
+
+/*
+ * This notifier function is called for the pre-rate and post-rate change
+ * notifications of the parent clock of cpuclk.
+ */
+static int exynos_cpuclk_notifier_cb(struct notifier_block *nb,
+				unsigned long event, void *data)
+{
+	struct clk_notifier_data *ndata = data;
+	struct exynos_cpuclk *cpuclk;
+	void __iomem *base;
+	int err = 0;
+
+	cpuclk = container_of(nb, struct exynos_cpuclk, clk_nb);
+	base = cpuclk->ctrl_base;
+
+	if (event == PRE_RATE_CHANGE)
+		err = exynos_cpuclk_pre_rate_change(ndata, cpuclk, base);
+	else if (event == POST_RATE_CHANGE)
+		err = exynos_cpuclk_post_rate_change(ndata, cpuclk, base);
+
+	return notifier_from_errno(err);
+}
+
+/* helper function to register a CPU clock */
+int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
+		unsigned int lookup_id, const char *name, const char *parent,
+		const char *alt_parent, unsigned long offset,
+		const struct exynos_cpuclk_cfg_data *cfg,
+		unsigned long num_cfgs, unsigned long flags)
+{
+	struct exynos_cpuclk *cpuclk;
+	struct clk_init_data init;
+	struct clk *clk;
+	int ret = 0;
+
+	cpuclk = kzalloc(sizeof(*cpuclk), GFP_KERNEL);
+	if (!cpuclk)
+		return -ENOMEM;
+
+	init.name = name;
+	init.flags = CLK_SET_RATE_PARENT;
+	init.parent_names = &parent;
+	init.num_parents = 1;
+	init.ops = &exynos_cpuclk_clk_ops;
+
+	cpuclk->hw.init = &init;
+	cpuclk->ctrl_base = ctx->reg_base + offset;
+	cpuclk->lock = &ctx->lock;
+	cpuclk->flags = flags;
+	cpuclk->clk_nb.notifier_call = exynos_cpuclk_notifier_cb;
+
+	cpuclk->alt_parent = __clk_lookup(alt_parent);
+	if (!cpuclk->alt_parent) {
+		pr_err("%s: could not lookup alternate parent %s\n",
+				__func__, alt_parent);
+		ret = -EINVAL;
+		goto free_cpuclk;
+	}
+
+	clk = __clk_lookup(parent);
+	if (!clk) {
+		pr_err("%s: could not lookup parent clock %s\n",
+				__func__, parent);
+		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;
+	}
+
+	cpuclk->cfg = kmemdup(cfg, sizeof(*cfg) * num_cfgs, GFP_KERNEL);
+	if (!cpuclk->cfg) {
+		pr_err("%s: could not allocate memory for cpuclk data\n",
+				__func__);
+		ret = -ENOMEM;
+		goto unregister_clk_nb;
+	}
+
+	clk = 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_cpuclk_data;
+	}
+
+	samsung_clk_add_lookup(ctx, clk, lookup_id);
+	return 0;
+
+free_cpuclk_data:
+	kfree(cpuclk->cfg);
+unregister_clk_nb:
+	clk_notifier_unregister(__clk_lookup(parent), &cpuclk->clk_nb);
+free_cpuclk:
+	kfree(cpuclk);
+	return ret;
+}

drivers/clk/samsung/clk-cpu.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ *
+ * 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.
+ *
+ * Common Clock Framework support for all PLL's in Samsung platforms
+*/
+
+#ifndef __SAMSUNG_CLK_CPU_H
+#define __SAMSUNG_CLK_CPU_H
+
+#include "clk.h"
+
+/**
+ * struct exynos_cpuclk_data: config data to setup cpu clocks.
+ * @prate: frequency of the primary parent clock (in KHz).
+ * @div0: value to be programmed in the div_cpu0 register.
+ * @div1: value to be programmed in the div_cpu1 register.
+ *
+ * This structure holds the divider configuration data for dividers in the CPU
+ * clock domain. The parent frequency at which these divider values are valid is
+ * specified in @prate. The @prate is the frequency of the primary parent clock.
+ * For CPU clock domains that do not have a DIV1 register, the @div1 member
+ * value is not used.
+ */
+struct exynos_cpuclk_cfg_data {
+	unsigned long	prate;
+	unsigned long	div0;
+	unsigned long	div1;
+};
+
+/**
+ * struct exynos_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.
+ * @ctrl_base:	base address of the clock controller.
+ * @lock: cpu clock domain register access lock.
+ * @cfg: cpu clock rate configuration data.
+ * @num_cfgs: number of array elements in @cfg array.
+ * @clk_nb: clock notifier registered for changes in clock speed of the
+ *	primary parent clock.
+ * @flags: configuration flags for the CPU clock.
+ *
+ * This structure holds information required for programming the CPU clock for
+ * various clock speeds.
+ */
+struct exynos_cpuclk {
+	struct clk_hw				hw;
+	struct clk				*alt_parent;
+	void __iomem				*ctrl_base;
+	spinlock_t				*lock;
+	const struct exynos_cpuclk_cfg_data	*cfg;
+	const unsigned long			num_cfgs;
+	struct notifier_block			clk_nb;
+	unsigned long				flags;
+
+/* The CPU clock registers has DIV1 configuration register */
+#define CLK_CPU_HAS_DIV1		(1 << 0)
+/* When ALT parent is active, debug clocks need safe divider values */
+#define CLK_CPU_NEEDS_DEBUG_ALT_DIV	(1 << 1)
+};
+
+extern int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
+			unsigned int lookup_id, const char *name,
+			const char *parent, const char *alt_parent,
+			unsigned long offset,
+			const struct exynos_cpuclk_cfg_data *cfg,
+			unsigned long num_cfgs, unsigned long flags);
+
+#endif /* __SAMSUNG_CLK_CPU_H */