clk: tegra: Add library for the DFLL clock source (open-loop mode)

Add shared code to support the Tegra DFLL clocksource in open-loop
mode. This root clocksource is present on the Tegra124 SoCs. The
DFLL is the intended primary clock source for the fast CPU cluster.

This code is very closely based on a patch by Paul Walmsley from
December (http://comments.gmane.org/gmane.linux.ports.tegra/15273),
which in turn comes from the internal driver by originally created
by Aleksandr Frid <afrid@nvidia.com>.

Subsequent patches will add support for closed loop mode and drivers
for the Tegra124 fast CPU cluster DFLL devices, which rely on this
code.

Signed-off-by: Paul Walmsley <pwalmsley@nvidia.com>
Signed-off-by: Tuomas Tynkkynen <ttynkkynen@nvidia.com>
Signed-off-by: Mikko Perttunen <mikko.perttunen@kapsi.fi>
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Acked-by: Michael Turquette <mturquette@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/clk/tegra/Makefile

@@ -1,5 +1,6 @@
 obj-y					+= clk.o
 obj-y					+= clk-audio-sync.o
+obj-y					+= clk-dfll.o
 obj-y					+= clk-divider.o
 obj-y					+= clk-periph.o
 obj-y					+= clk-periph-gate.o

drivers/clk/tegra/clk-dfll.c

@@ -0,0 +1,1095 @@
+/*
+ * clk-dfll.c - Tegra DFLL clock source common code
+ *
+ * Copyright (C) 2012-2014 NVIDIA Corporation. All rights reserved.
+ *
+ * Aleksandr Frid <afrid@nvidia.com>
+ * Paul Walmsley <pwalmsley@nvidia.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 program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * This library is for the DVCO and DFLL IP blocks on the Tegra124
+ * SoC. These IP blocks together are also known at NVIDIA as
+ * "CL-DVFS". To try to avoid confusion, this code refers to them
+ * collectively as the "DFLL."
+ *
+ * The DFLL is a root clocksource which tolerates some amount of
+ * supply voltage noise. Tegra124 uses it to clock the fast CPU
+ * complex when the target CPU speed is above a particular rate. The
+ * DFLL can be operated in either open-loop mode or closed-loop mode.
+ * In open-loop mode, the DFLL generates an output clock appropriate
+ * to the supply voltage. In closed-loop mode, when configured with a
+ * target frequency, the DFLL minimizes supply voltage while
+ * delivering an average frequency equal to the target.
+ *
+ * Devices clocked by the DFLL must be able to tolerate frequency
+ * variation. In the case of the CPU, it's important to note that the
+ * CPU cycle time will vary. This has implications for
+ * performance-measurement code and any code that relies on the CPU
+ * cycle time to delay for a certain length of time.
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm_opp.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/reset.h>
+#include <linux/seq_file.h>
+
+#include "clk-dfll.h"
+
+/*
+ * DFLL control registers - access via dfll_{readl,writel}
+ */
+
+/* DFLL_CTRL: DFLL control register */
+#define DFLL_CTRL			0x00
+#define DFLL_CTRL_MODE_MASK		0x03
+
+/* DFLL_CONFIG: DFLL sample rate control */
+#define DFLL_CONFIG			0x04
+#define DFLL_CONFIG_DIV_MASK		0xff
+#define DFLL_CONFIG_DIV_PRESCALE	32
+
+/* DFLL_PARAMS: tuning coefficients for closed loop integrator */
+#define DFLL_PARAMS			0x08
+#define DFLL_PARAMS_CG_SCALE		(0x1 << 24)
+#define DFLL_PARAMS_FORCE_MODE_SHIFT	22
+#define DFLL_PARAMS_FORCE_MODE_MASK	(0x3 << DFLL_PARAMS_FORCE_MODE_SHIFT)
+#define DFLL_PARAMS_CF_PARAM_SHIFT	16
+#define DFLL_PARAMS_CF_PARAM_MASK	(0x3f << DFLL_PARAMS_CF_PARAM_SHIFT)
+#define DFLL_PARAMS_CI_PARAM_SHIFT	8
+#define DFLL_PARAMS_CI_PARAM_MASK	(0x7 << DFLL_PARAMS_CI_PARAM_SHIFT)
+#define DFLL_PARAMS_CG_PARAM_SHIFT	0
+#define DFLL_PARAMS_CG_PARAM_MASK	(0xff << DFLL_PARAMS_CG_PARAM_SHIFT)
+
+/* DFLL_TUNE0: delay line configuration register 0 */
+#define DFLL_TUNE0			0x0c
+
+/* DFLL_TUNE1: delay line configuration register 1 */
+#define DFLL_TUNE1			0x10
+
+/* DFLL_FREQ_REQ: target DFLL frequency control */
+#define DFLL_FREQ_REQ			0x14
+#define DFLL_FREQ_REQ_FORCE_ENABLE	(0x1 << 28)
+#define DFLL_FREQ_REQ_FORCE_SHIFT	16
+#define DFLL_FREQ_REQ_FORCE_MASK	(0xfff << DFLL_FREQ_REQ_FORCE_SHIFT)
+#define FORCE_MAX			2047
+#define FORCE_MIN			-2048
+#define DFLL_FREQ_REQ_SCALE_SHIFT	8
+#define DFLL_FREQ_REQ_SCALE_MASK	(0xff << DFLL_FREQ_REQ_SCALE_SHIFT)
+#define DFLL_FREQ_REQ_SCALE_MAX		256
+#define DFLL_FREQ_REQ_FREQ_VALID	(0x1 << 7)
+#define DFLL_FREQ_REQ_MULT_SHIFT	0
+#define DFLL_FREQ_REG_MULT_MASK		(0x7f << DFLL_FREQ_REQ_MULT_SHIFT)
+#define FREQ_MAX			127
+
+/* DFLL_DROOP_CTRL: droop prevention control */
+#define DFLL_DROOP_CTRL			0x1c
+
+/* DFLL_OUTPUT_CFG: closed loop mode control registers */
+/* NOTE: access via dfll_i2c_{readl,writel} */
+#define DFLL_OUTPUT_CFG			0x20
+#define DFLL_OUTPUT_CFG_I2C_ENABLE	(0x1 << 30)
+#define OUT_MASK			0x3f
+#define DFLL_OUTPUT_CFG_SAFE_SHIFT	24
+#define DFLL_OUTPUT_CFG_SAFE_MASK	\
+		(OUT_MASK << DFLL_OUTPUT_CFG_SAFE_SHIFT)
+#define DFLL_OUTPUT_CFG_MAX_SHIFT	16
+#define DFLL_OUTPUT_CFG_MAX_MASK	\
+		(OUT_MASK << DFLL_OUTPUT_CFG_MAX_SHIFT)
+#define DFLL_OUTPUT_CFG_MIN_SHIFT	8
+#define DFLL_OUTPUT_CFG_MIN_MASK	\
+		(OUT_MASK << DFLL_OUTPUT_CFG_MIN_SHIFT)
+#define DFLL_OUTPUT_CFG_PWM_DELTA	(0x1 << 7)
+#define DFLL_OUTPUT_CFG_PWM_ENABLE	(0x1 << 6)
+#define DFLL_OUTPUT_CFG_PWM_DIV_SHIFT	0
+#define DFLL_OUTPUT_CFG_PWM_DIV_MASK	\
+		(OUT_MASK << DFLL_OUTPUT_CFG_PWM_DIV_SHIFT)
+
+/* DFLL_OUTPUT_FORCE: closed loop mode voltage forcing control */
+#define DFLL_OUTPUT_FORCE		0x24
+#define DFLL_OUTPUT_FORCE_ENABLE	(0x1 << 6)
+#define DFLL_OUTPUT_FORCE_VALUE_SHIFT	0
+#define DFLL_OUTPUT_FORCE_VALUE_MASK	\
+		(OUT_MASK << DFLL_OUTPUT_FORCE_VALUE_SHIFT)
+
+/* DFLL_MONITOR_CTRL: internal monitor data source control */
+#define DFLL_MONITOR_CTRL		0x28
+#define DFLL_MONITOR_CTRL_FREQ		6
+
+/* DFLL_MONITOR_DATA: internal monitor data output */
+#define DFLL_MONITOR_DATA		0x2c
+#define DFLL_MONITOR_DATA_NEW_MASK	(0x1 << 16)
+#define DFLL_MONITOR_DATA_VAL_SHIFT	0
+#define DFLL_MONITOR_DATA_VAL_MASK	(0xFFFF << DFLL_MONITOR_DATA_VAL_SHIFT)
+
+/*
+ * I2C output control registers - access via dfll_i2c_{readl,writel}
+ */
+
+/* DFLL_I2C_CFG: I2C controller configuration register */
+#define DFLL_I2C_CFG			0x40
+#define DFLL_I2C_CFG_ARB_ENABLE		(0x1 << 20)
+#define DFLL_I2C_CFG_HS_CODE_SHIFT	16
+#define DFLL_I2C_CFG_HS_CODE_MASK	(0x7 << DFLL_I2C_CFG_HS_CODE_SHIFT)
+#define DFLL_I2C_CFG_PACKET_ENABLE	(0x1 << 15)
+#define DFLL_I2C_CFG_SIZE_SHIFT		12
+#define DFLL_I2C_CFG_SIZE_MASK		(0x7 << DFLL_I2C_CFG_SIZE_SHIFT)
+#define DFLL_I2C_CFG_SLAVE_ADDR_10	(0x1 << 10)
+#define DFLL_I2C_CFG_SLAVE_ADDR_SHIFT_7BIT	1
+#define DFLL_I2C_CFG_SLAVE_ADDR_SHIFT_10BIT	0
+
+/* DFLL_I2C_VDD_REG_ADDR: PMIC I2C address for closed loop mode */
+#define DFLL_I2C_VDD_REG_ADDR		0x44
+
+/* DFLL_I2C_STS: I2C controller status */
+#define DFLL_I2C_STS			0x48
+#define DFLL_I2C_STS_I2C_LAST_SHIFT	1
+#define DFLL_I2C_STS_I2C_REQ_PENDING	0x1
+
+/* DFLL_INTR_STS: DFLL interrupt status register */
+#define DFLL_INTR_STS			0x5c
+
+/* DFLL_INTR_EN: DFLL interrupt enable register */
+#define DFLL_INTR_EN			0x60
+#define DFLL_INTR_MIN_MASK		0x1
+#define DFLL_INTR_MAX_MASK		0x2
+
+/*
+ * Integrated I2C controller registers - relative to td->i2c_controller_base
+ */
+
+/* DFLL_I2C_CLK_DIVISOR: I2C controller clock divisor */
+#define DFLL_I2C_CLK_DIVISOR		0x6c
+#define DFLL_I2C_CLK_DIVISOR_MASK	0xffff
+#define DFLL_I2C_CLK_DIVISOR_FS_SHIFT	16
+#define DFLL_I2C_CLK_DIVISOR_HS_SHIFT	0
+#define DFLL_I2C_CLK_DIVISOR_PREDIV	8
+#define DFLL_I2C_CLK_DIVISOR_HSMODE_PREDIV	12
+
+/*
+ * Other constants
+ */
+
+/* MAX_DFLL_VOLTAGES: number of LUT entries in the DFLL IP block */
+#define MAX_DFLL_VOLTAGES		33
+
+/*
+ * REF_CLK_CYC_PER_DVCO_SAMPLE: the number of ref_clk cycles that the hardware
+ *    integrates the DVCO counter over - used for debug rate monitoring and
+ *    droop control
+ */
+#define REF_CLK_CYC_PER_DVCO_SAMPLE	4
+
+/*
+ * REF_CLOCK_RATE: the DFLL reference clock rate currently supported by this
+ * driver, in Hz
+ */
+#define REF_CLOCK_RATE			51000000UL
+
+
+/**
+ * enum dfll_ctrl_mode - DFLL hardware operating mode
+ * @DFLL_UNINITIALIZED: (uninitialized state - not in hardware bitfield)
+ * @DFLL_DISABLED: DFLL not generating an output clock
+ * @DFLL_OPEN_LOOP: DVCO running, but DFLL not adjusting voltage
+ *
+ * The integer corresponding to the last two states, minus one, is
+ * written to the DFLL hardware to change operating modes.
+ */
+enum dfll_ctrl_mode {
+	DFLL_UNINITIALIZED = 0,
+	DFLL_DISABLED = 1,
+	DFLL_OPEN_LOOP = 2,
+};
+
+/**
+ * enum dfll_tune_range - voltage range that the driver believes it's in
+ * @DFLL_TUNE_UNINITIALIZED: DFLL tuning not yet programmed
+ * @DFLL_TUNE_LOW: DFLL in the low-voltage range (or open-loop mode)
+ *
+ * Some DFLL tuning parameters may need to change depending on the
+ * DVCO's voltage; these states represent the ranges that the driver
+ * supports. These are software states; these values are never
+ * written into registers.
+ */
+enum dfll_tune_range {
+	DFLL_TUNE_UNINITIALIZED = 0,
+	DFLL_TUNE_LOW = 1,
+};
+
+struct tegra_dfll {
+	struct device			*dev;
+	struct tegra_dfll_soc_data	*soc;
+
+	void __iomem			*base;
+	void __iomem			*i2c_base;
+	void __iomem			*i2c_controller_base;
+	void __iomem			*lut_base;
+
+	struct regulator		*vdd_reg;
+	struct clk			*soc_clk;
+	struct clk			*ref_clk;
+	struct clk			*i2c_clk;
+	struct clk			*dfll_clk;
+	struct reset_control		*dvco_rst;
+	unsigned long			ref_rate;
+	unsigned long			i2c_clk_rate;
+	unsigned long			dvco_rate_min;
+
+	enum dfll_ctrl_mode		mode;
+	enum dfll_tune_range		tune_range;
+	struct dentry			*debugfs_dir;
+	struct clk_hw			dfll_clk_hw;
+	const char			*output_clock_name;
+
+	/* Parameters from DT */
+	u32				droop_ctrl;
+};
+
+#define clk_hw_to_dfll(_hw) container_of(_hw, struct tegra_dfll, dfll_clk_hw)
+
+/* mode_name: map numeric DFLL modes to names for friendly console messages */
+static const char * const mode_name[] = {
+	[DFLL_UNINITIALIZED] = "uninitialized",
+	[DFLL_DISABLED] = "disabled",
+	[DFLL_OPEN_LOOP] = "open_loop",
+};
+
+/*
+ * Register accessors
+ */
+
+static inline u32 dfll_readl(struct tegra_dfll *td, u32 offs)
+{
+	return __raw_readl(td->base + offs);
+}
+
+static inline void dfll_writel(struct tegra_dfll *td, u32 val, u32 offs)
+{
+	WARN_ON(offs >= DFLL_I2C_CFG);
+	__raw_writel(val, td->base + offs);
+}
+
+static inline void dfll_wmb(struct tegra_dfll *td)
+{
+	dfll_readl(td, DFLL_CTRL);
+}
+
+/* I2C output control registers - for addresses above DFLL_I2C_CFG */
+
+static inline u32 dfll_i2c_readl(struct tegra_dfll *td, u32 offs)
+{
+	return __raw_readl(td->i2c_base + offs);
+}
+
+static inline void dfll_i2c_writel(struct tegra_dfll *td, u32 val, u32 offs)
+{
+	__raw_writel(val, td->i2c_base + offs);
+}
+
+static inline void dfll_i2c_wmb(struct tegra_dfll *td)
+{
+	dfll_i2c_readl(td, DFLL_I2C_CFG);
+}
+
+/**
+ * dfll_is_running - is the DFLL currently generating a clock?
+ * @td: DFLL instance
+ *
+ * If the DFLL is currently generating an output clock signal, return
+ * true; otherwise return false.
+ */
+static bool dfll_is_running(struct tegra_dfll *td)
+{
+	return td->mode >= DFLL_OPEN_LOOP;
+}
+
+/*
+ * Runtime PM suspend/resume callbacks
+ */
+
+/**
+ * tegra_dfll_runtime_resume - enable all clocks needed by the DFLL
+ * @dev: DFLL device *
+ *
+ * Enable all clocks needed by the DFLL. Assumes that clk_prepare()
+ * has already been called on all the clocks.
+ *
+ * XXX Should also handle context restore when returning from off.
+ */
+int tegra_dfll_runtime_resume(struct device *dev)
+{
+	struct tegra_dfll *td = dev_get_drvdata(dev);
+	int ret;
+
+	ret = clk_enable(td->ref_clk);
+	if (ret) {
+		dev_err(dev, "could not enable ref clock: %d\n", ret);
+		return ret;
+	}
+
+	ret = clk_enable(td->soc_clk);
+	if (ret) {
+		dev_err(dev, "could not enable register clock: %d\n", ret);
+		clk_disable(td->ref_clk);
+		return ret;
+	}
+
+	ret = clk_enable(td->i2c_clk);
+	if (ret) {
+		dev_err(dev, "could not enable i2c clock: %d\n", ret);
+		clk_disable(td->soc_clk);
+		clk_disable(td->ref_clk);
+		return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(tegra_dfll_runtime_resume);
+
+/**
+ * tegra_dfll_runtime_suspend - disable all clocks needed by the DFLL
+ * @dev: DFLL device *
+ *
+ * Disable all clocks needed by the DFLL. Assumes that other code
+ * will later call clk_unprepare().
+ */
+int tegra_dfll_runtime_suspend(struct device *dev)
+{
+	struct tegra_dfll *td = dev_get_drvdata(dev);
+
+	clk_disable(td->ref_clk);
+	clk_disable(td->soc_clk);
+	clk_disable(td->i2c_clk);
+
+	return 0;
+}
+EXPORT_SYMBOL(tegra_dfll_runtime_suspend);
+
+/*
+ * DFLL tuning operations (per-voltage-range tuning settings)
+ */
+
+/**
+ * dfll_tune_low - tune to DFLL and CPU settings valid for any voltage
+ * @td: DFLL instance
+ *
+ * Tune the DFLL oscillator parameters and the CPU clock shaper for
+ * the low-voltage range. These settings are valid for any voltage,
+ * but may not be optimal.
+ */
+static void dfll_tune_low(struct tegra_dfll *td)
+{
+	td->tune_range = DFLL_TUNE_LOW;
+
+	dfll_writel(td, td->soc->tune0_low, DFLL_TUNE0);
+	dfll_writel(td, td->soc->tune1, DFLL_TUNE1);
+	dfll_wmb(td);
+
+	if (td->soc->set_clock_trimmers_low)
+		td->soc->set_clock_trimmers_low();
+}
+
+/*
+ * Output clock scaler helpers
+ */
+
+/**
+ * dfll_scale_dvco_rate - calculate scaled rate from the DVCO rate
+ * @scale_bits: clock scaler value (bits in the DFLL_FREQ_REQ_SCALE field)
+ * @dvco_rate: the DVCO rate
+ *
+ * Apply the same scaling formula that the DFLL hardware uses to scale
+ * the DVCO rate.
+ */
+static unsigned long dfll_scale_dvco_rate(int scale_bits,
+					  unsigned long dvco_rate)
+{
+	return (u64)dvco_rate * (scale_bits + 1) / DFLL_FREQ_REQ_SCALE_MAX;
+}
+
+/*
+ * Monitor control
+ */
+
+/**
+ * dfll_calc_monitored_rate - convert DFLL_MONITOR_DATA_VAL rate into real freq
+ * @monitor_data: value read from the DFLL_MONITOR_DATA_VAL bitfield
+ * @ref_rate: DFLL reference clock rate
+ *
+ * Convert @monitor_data from DFLL_MONITOR_DATA_VAL units into cycles
+ * per second. Returns the converted value.
+ */
+static u64 dfll_calc_monitored_rate(u32 monitor_data,
+				    unsigned long ref_rate)
+{
+	return monitor_data * (ref_rate / REF_CLK_CYC_PER_DVCO_SAMPLE);
+}
+
+/**
+ * dfll_read_monitor_rate - return the DFLL's output rate from internal monitor
+ * @td: DFLL instance
+ *
+ * If the DFLL is enabled, return the last rate reported by the DFLL's
+ * internal monitoring hardware. This works in both open-loop and
+ * closed-loop mode, and takes the output scaler setting into account.
+ * Assumes that the monitor was programmed to monitor frequency before
+ * the sample period started. If the driver believes that the DFLL is
+ * currently uninitialized or disabled, it will return 0, since
+ * otherwise the DFLL monitor data register will return the last
+ * measured rate from when the DFLL was active.
+ */
+static u64 dfll_read_monitor_rate(struct tegra_dfll *td)
+{
+	u32 v, s;
+	u64 pre_scaler_rate, post_scaler_rate;
+
+	if (!dfll_is_running(td))
+		return 0;
+
+	v = dfll_readl(td, DFLL_MONITOR_DATA);
+	v = (v & DFLL_MONITOR_DATA_VAL_MASK) >> DFLL_MONITOR_DATA_VAL_SHIFT;
+	pre_scaler_rate = dfll_calc_monitored_rate(v, td->ref_rate);
+
+	s = dfll_readl(td, DFLL_FREQ_REQ);
+	s = (s & DFLL_FREQ_REQ_SCALE_MASK) >> DFLL_FREQ_REQ_SCALE_SHIFT;
+	post_scaler_rate = dfll_scale_dvco_rate(s, pre_scaler_rate);
+
+	return post_scaler_rate;
+}
+
+/*
+ * DFLL mode switching
+ */
+
+/**
+ * dfll_set_mode - change the DFLL control mode
+ * @td: DFLL instance
+ * @mode: DFLL control mode (see enum dfll_ctrl_mode)
+ *
+ * Change the DFLL's operating mode between disabled, open-loop mode,
+ * and closed-loop mode, or vice versa.
+ */
+static void dfll_set_mode(struct tegra_dfll *td,
+			  enum dfll_ctrl_mode mode)
+{
+	td->mode = mode;
+	dfll_writel(td, mode - 1, DFLL_CTRL);
+	dfll_wmb(td);
+}
+
+/*
+ * DFLL enable/disable & open-loop <-> closed-loop transitions
+ */
+
+/**
+ * dfll_disable - switch from open-loop mode to disabled mode
+ * @td: DFLL instance
+ *
+ * Switch from OPEN_LOOP state to DISABLED state. Returns 0 upon success
+ * or -EPERM if the DFLL is not currently in open-loop mode.
+ */
+static int dfll_disable(struct tegra_dfll *td)
+{
+	if (td->mode != DFLL_OPEN_LOOP) {
+		dev_err(td->dev, "cannot disable DFLL in %s mode\n",
+			mode_name[td->mode]);
+		return -EINVAL;
+	}
+
+	dfll_set_mode(td, DFLL_DISABLED);
+	pm_runtime_put_sync(td->dev);
+
+	return 0;
+}
+
+/**
+ * dfll_enable - switch a disabled DFLL to open-loop mode
+ * @td: DFLL instance
+ *
+ * Switch from DISABLED state to OPEN_LOOP state. Returns 0 upon success
+ * or -EPERM if the DFLL is not currently disabled.
+ */
+static int dfll_enable(struct tegra_dfll *td)
+{
+	if (td->mode != DFLL_DISABLED) {
+		dev_err(td->dev, "cannot enable DFLL in %s mode\n",
+			mode_name[td->mode]);
+		return -EPERM;
+	}
+
+	pm_runtime_get_sync(td->dev);
+	dfll_set_mode(td, DFLL_OPEN_LOOP);
+
+	return 0;
+}
+
+/**
+ * dfll_set_open_loop_config - prepare to switch to open-loop mode
+ * @td: DFLL instance
+ *
+ * Prepare to switch the DFLL to open-loop mode. This switches the
+ * DFLL to the low-voltage tuning range, ensures that I2C output
+ * forcing is disabled, and disables the output clock rate scaler.
+ * The DFLL's low-voltage tuning range parameters must be
+ * characterized to keep the downstream device stable at any DVCO
+ * input voltage. No return value.
+ */
+static void dfll_set_open_loop_config(struct tegra_dfll *td)
+{
+	u32 val;
+
+	/* always tune low (safe) in open loop */
+	if (td->tune_range != DFLL_TUNE_LOW)
+		dfll_tune_low(td);
+
+	val = dfll_readl(td, DFLL_FREQ_REQ);
+	val |= DFLL_FREQ_REQ_SCALE_MASK;
+	val &= ~DFLL_FREQ_REQ_FORCE_ENABLE;
+	dfll_writel(td, val, DFLL_FREQ_REQ);
+	dfll_wmb(td);
+}
+
+/*
+ * Clock framework integration
+ */
+
+static int dfll_clk_is_enabled(struct clk_hw *hw)
+{
+	struct tegra_dfll *td = clk_hw_to_dfll(hw);
+
+	return dfll_is_running(td);
+}
+
+static int dfll_clk_enable(struct clk_hw *hw)
+{
+	struct tegra_dfll *td = clk_hw_to_dfll(hw);
+
+	return dfll_enable(td);
+}
+
+static void dfll_clk_disable(struct clk_hw *hw)
+{
+	struct tegra_dfll *td = clk_hw_to_dfll(hw);
+
+	dfll_disable(td);
+}
+
+static const struct clk_ops dfll_clk_ops = {
+	.is_enabled	= dfll_clk_is_enabled,
+	.enable		= dfll_clk_enable,
+	.disable	= dfll_clk_disable,
+};
+
+static struct clk_init_data dfll_clk_init_data = {
+	.flags		= CLK_IS_ROOT,
+	.ops		= &dfll_clk_ops,
+	.num_parents	= 0,
+};
+
+/**
+ * dfll_register_clk - register the DFLL output clock with the clock framework
+ * @td: DFLL instance
+ *
+ * Register the DFLL's output clock with the Linux clock framework and register
+ * the DFLL driver as an OF clock provider. Returns 0 upon success or -EINVAL
+ * or -ENOMEM upon failure.
+ */
+static int dfll_register_clk(struct tegra_dfll *td)
+{
+	int ret;
+
+	dfll_clk_init_data.name = td->output_clock_name;
+	td->dfll_clk_hw.init = &dfll_clk_init_data;
+
+	td->dfll_clk = clk_register(td->dev, &td->dfll_clk_hw);
+	if (IS_ERR(td->dfll_clk)) {
+		dev_err(td->dev, "DFLL clock registration error\n");
+		return -EINVAL;
+	}
+
+	ret = of_clk_add_provider(td->dev->of_node, of_clk_src_simple_get,
+				  td->dfll_clk);
+	if (ret) {
+		dev_err(td->dev, "of_clk_add_provider() failed\n");
+
+		clk_unregister(td->dfll_clk);
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * dfll_unregister_clk - unregister the DFLL output clock
+ * @td: DFLL instance
+ *
+ * Unregister the DFLL's output clock from the Linux clock framework
+ * and from clkdev. No return value.
+ */
+static void dfll_unregister_clk(struct tegra_dfll *td)
+{
+	of_clk_del_provider(td->dev->of_node);
+	clk_unregister(td->dfll_clk);
+	td->dfll_clk = NULL;
+}
+
+/*
+ * Debugfs interface
+ */
+
+#ifdef CONFIG_DEBUG_FS
+
+static int attr_enable_get(void *data, u64 *val)
+{
+	struct tegra_dfll *td = data;
+
+	*val = dfll_is_running(td);
+
+	return 0;
+}
+static int attr_enable_set(void *data, u64 val)
+{
+	struct tegra_dfll *td = data;
+
+	return val ? dfll_enable(td) : dfll_disable(td);
+}
+DEFINE_SIMPLE_ATTRIBUTE(enable_fops, attr_enable_get, attr_enable_set,
+			"%llu\n");
+
+static int attr_rate_get(void *data, u64 *val)
+{
+	struct tegra_dfll *td = data;
+
+	*val = dfll_read_monitor_rate(td);
+
+	return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(rate_fops, attr_rate_get, NULL, "%llu\n");
+
+static int attr_registers_show(struct seq_file *s, void *data)
+{
+	u32 val, offs;
+	struct tegra_dfll *td = s->private;
+
+	seq_puts(s, "CONTROL REGISTERS:\n");
+	for (offs = 0; offs <= DFLL_MONITOR_DATA; offs += 4) {
+		if (offs == DFLL_OUTPUT_CFG)
+			val = dfll_i2c_readl(td, offs);
+		else
+			val = dfll_readl(td, offs);
+		seq_printf(s, "[0x%02x] = 0x%08x\n", offs, val);
+	}
+
+	seq_puts(s, "\nI2C and INTR REGISTERS:\n");
+	for (offs = DFLL_I2C_CFG; offs <= DFLL_I2C_STS; offs += 4)
+		seq_printf(s, "[0x%02x] = 0x%08x\n", offs,
+			   dfll_i2c_readl(td, offs));
+	for (offs = DFLL_INTR_STS; offs <= DFLL_INTR_EN; offs += 4)
+		seq_printf(s, "[0x%02x] = 0x%08x\n", offs,
+			   dfll_i2c_readl(td, offs));
+
+	seq_puts(s, "\nINTEGRATED I2C CONTROLLER REGISTERS:\n");
+	offs = DFLL_I2C_CLK_DIVISOR;
+	seq_printf(s, "[0x%02x] = 0x%08x\n", offs,
+		   __raw_readl(td->i2c_controller_base + offs));
+
+	seq_puts(s, "\nLUT:\n");
+	for (offs = 0; offs <  4 * MAX_DFLL_VOLTAGES; offs += 4)
+		seq_printf(s, "[0x%02x] = 0x%08x\n", offs,
+			   __raw_readl(td->lut_base + offs));
+
+	return 0;
+}
+
+static int attr_registers_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, attr_registers_show, inode->i_private);
+}
+
+static const struct file_operations attr_registers_fops = {
+	.open		= attr_registers_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static int dfll_debug_init(struct tegra_dfll *td)
+{
+	int ret;
+
+	if (!td || (td->mode == DFLL_UNINITIALIZED))
+		return 0;
+
+	td->debugfs_dir = debugfs_create_dir("tegra_dfll_fcpu", NULL);
+	if (!td->debugfs_dir)
+		return -ENOMEM;
+
+	ret = -ENOMEM;
+
+	if (!debugfs_create_file("enable", S_IRUGO | S_IWUSR,
+				 td->debugfs_dir, td, &enable_fops))
+		goto err_out;
+
+	if (!debugfs_create_file("rate", S_IRUGO,
+				 td->debugfs_dir, td, &rate_fops))
+		goto err_out;
+
+	if (!debugfs_create_file("registers", S_IRUGO,
+				 td->debugfs_dir, td, &attr_registers_fops))
+		goto err_out;
+
+	return 0;
+
+err_out:
+	debugfs_remove_recursive(td->debugfs_dir);
+	return ret;
+}
+
+#endif /* CONFIG_DEBUG_FS */
+
+/*
+ * DFLL initialization
+ */
+
+/**
+ * dfll_set_default_params - program non-output related DFLL parameters
+ * @td: DFLL instance
+ *
+ * During DFLL driver initialization or resume from context loss,
+ * program parameters for the closed loop integrator, DVCO tuning,
+ * voltage droop control and monitor control.
+ */
+static void dfll_set_default_params(struct tegra_dfll *td)
+{
+	dfll_tune_low(td);
+	dfll_writel(td, td->droop_ctrl, DFLL_DROOP_CTRL);
+	dfll_writel(td, DFLL_MONITOR_CTRL_FREQ, DFLL_MONITOR_CTRL);
+}
+
+/**
+ * dfll_init_clks - clk_get() the DFLL source clocks
+ * @td: DFLL instance
+ *
+ * Call clk_get() on the DFLL source clocks and save the pointers for later
+ * use. Returns 0 upon success or error (see devm_clk_get) if one or more
+ * of the clocks couldn't be looked up.
+ */
+static int dfll_init_clks(struct tegra_dfll *td)
+{
+	td->ref_clk = devm_clk_get(td->dev, "ref");
+	if (IS_ERR(td->ref_clk)) {
+		dev_err(td->dev, "missing ref clock\n");
+		return PTR_ERR(td->ref_clk);
+	}
+
+	td->soc_clk = devm_clk_get(td->dev, "soc");
+	if (IS_ERR(td->soc_clk)) {
+		dev_err(td->dev, "missing soc clock\n");
+		return PTR_ERR(td->soc_clk);
+	}
+
+	td->i2c_clk = devm_clk_get(td->dev, "i2c");
+	if (IS_ERR(td->i2c_clk)) {
+		dev_err(td->dev, "missing i2c clock\n");
+		return PTR_ERR(td->i2c_clk);
+	}
+	td->i2c_clk_rate = clk_get_rate(td->i2c_clk);
+
+	return 0;
+}
+
+/**
+ * dfll_init - Prepare the DFLL IP block for use
+ * @td: DFLL instance
+ *
+ * Do everything necessary to prepare the DFLL IP block for use. The
+ * DFLL will be left in DISABLED state. Called by dfll_probe().
+ * Returns 0 upon success, or passes along the error from whatever
+ * function returned it.
+ */
+static int dfll_init(struct tegra_dfll *td)
+{
+	int ret;
+
+	td->ref_rate = clk_get_rate(td->ref_clk);
+	if (td->ref_rate != REF_CLOCK_RATE) {
+		dev_err(td->dev, "unexpected ref clk rate %lu, expecting %lu",
+			td->ref_rate, REF_CLOCK_RATE);
+		return -EINVAL;
+	}
+
+	reset_control_deassert(td->dvco_rst);
+
+	ret = clk_prepare(td->ref_clk);
+	if (ret) {
+		dev_err(td->dev, "failed to prepare ref_clk\n");
+		return ret;
+	}
+
+	ret = clk_prepare(td->soc_clk);
+	if (ret) {
+		dev_err(td->dev, "failed to prepare soc_clk\n");
+		goto di_err1;
+	}
+
+	ret = clk_prepare(td->i2c_clk);
+	if (ret) {
+		dev_err(td->dev, "failed to prepare i2c_clk\n");
+		goto di_err2;
+	}
+
+	pm_runtime_enable(td->dev);
+	pm_runtime_get_sync(td->dev);
+
+	dfll_set_mode(td, DFLL_DISABLED);
+	dfll_set_default_params(td);
+
+	if (td->soc->init_clock_trimmers)
+		td->soc->init_clock_trimmers();
+
+	dfll_set_open_loop_config(td);
+
+	pm_runtime_put_sync(td->dev);
+
+	return 0;
+
+di_err2:
+	clk_unprepare(td->soc_clk);
+di_err1:
+	clk_unprepare(td->ref_clk);
+
+	reset_control_assert(td->dvco_rst);
+
+	return ret;
+}
+
+/*
+ * DT data fetch
+ */
+
+/**
+ * read_dt_param - helper function for reading required parameters from the DT
+ * @td: DFLL instance
+ * @param: DT property name
+ * @dest: output pointer for the value read
+ *
+ * Read a required numeric parameter from the DFLL device node, or complain
+ * if the property doesn't exist. Returns a boolean indicating success for
+ * easy chaining of multiple calls to this function.
+ */
+static bool read_dt_param(struct tegra_dfll *td, const char *param, u32 *dest)
+{
+	int err = of_property_read_u32(td->dev->of_node, param, dest);
+
+	if (err < 0) {
+		dev_err(td->dev, "failed to read DT parameter %s: %d\n",
+			param, err);
+		return false;
+	}
+
+	return true;
+}
+
+/**
+ * dfll_fetch_common_params - read DFLL parameters from the device tree
+ * @td: DFLL instance
+ *
+ * Read all the DT parameters that are common to both I2C and PWM operation.
+ * Returns 0 on success or -EINVAL on any failure.
+ */
+static int dfll_fetch_common_params(struct tegra_dfll *td)
+{
+	bool ok = true;
+
+	ok &= read_dt_param(td, "nvidia,droop-ctrl", &td->droop_ctrl);
+
+	if (of_property_read_string(td->dev->of_node, "clock-output-names",
+				    &td->output_clock_name)) {
+		dev_err(td->dev, "missing clock-output-names property\n");
+		ok = false;
+	}
+
+	return ok ? 0 : -EINVAL;
+}
+
+/*
+ * API exported to per-SoC platform drivers
+ */
+
+/**
+ * tegra_dfll_register - probe a Tegra DFLL device
+ * @pdev: DFLL platform_device *
+ * @soc: Per-SoC integration and characterization data for this DFLL instance
+ *
+ * Probe and initialize a DFLL device instance. Intended to be called
+ * by a SoC-specific shim driver that passes in per-SoC integration
+ * and configuration data via @soc. Returns 0 on success or -err on failure.
+ */
+int tegra_dfll_register(struct platform_device *pdev,
+			struct tegra_dfll_soc_data *soc)
+{
+	struct resource *mem;
+	struct tegra_dfll *td;
+	int ret;
+
+	if (!soc) {
+		dev_err(&pdev->dev, "no tegra_dfll_soc_data provided\n");
+		return -EINVAL;
+	}
+
+	td = devm_kzalloc(&pdev->dev, sizeof(*td), GFP_KERNEL);
+	if (!td)
+		return -ENOMEM;
+	td->dev = &pdev->dev;
+	platform_set_drvdata(pdev, td);
+
+	td->soc = soc;
+
+	td->vdd_reg = devm_regulator_get(td->dev, "vdd-cpu");
+	if (IS_ERR(td->vdd_reg)) {
+		dev_err(td->dev, "couldn't get vdd_cpu regulator\n");
+		return PTR_ERR(td->vdd_reg);
+	}
+
+	td->dvco_rst = devm_reset_control_get(td->dev, "dvco");
+	if (IS_ERR(td->dvco_rst)) {
+		dev_err(td->dev, "couldn't get dvco reset\n");
+		return PTR_ERR(td->dvco_rst);
+	}
+
+	ret = dfll_fetch_common_params(td);
+	if (ret) {
+		dev_err(td->dev, "couldn't parse device tree parameters\n");
+		return ret;
+	}
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!mem) {
+		dev_err(td->dev, "no control register resource\n");
+		return -ENODEV;
+	}
+
+	td->base = devm_ioremap(td->dev, mem->start, resource_size(mem));
+	if (!td->base) {
+		dev_err(td->dev, "couldn't ioremap DFLL control registers\n");
+		return -ENODEV;
+	}
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	if (!mem) {
+		dev_err(td->dev, "no i2c_base resource\n");
+		return -ENODEV;
+	}
+
+	td->i2c_base = devm_ioremap(td->dev, mem->start, resource_size(mem));
+	if (!td->i2c_base) {
+		dev_err(td->dev, "couldn't ioremap i2c_base resource\n");
+		return -ENODEV;
+	}
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 2);
+	if (!mem) {
+		dev_err(td->dev, "no i2c_controller_base resource\n");
+		return -ENODEV;
+	}
+
+	td->i2c_controller_base = devm_ioremap(td->dev, mem->start,
+					       resource_size(mem));
+	if (!td->i2c_controller_base) {
+		dev_err(td->dev,
+			"couldn't ioremap i2c_controller_base resource\n");
+		return -ENODEV;
+	}
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 3);
+	if (!mem) {
+		dev_err(td->dev, "no lut_base resource\n");
+		return -ENODEV;
+	}
+
+	td->lut_base = devm_ioremap(td->dev, mem->start, resource_size(mem));
+	if (!td->lut_base) {
+		dev_err(td->dev,
+			"couldn't ioremap lut_base resource\n");
+		return -ENODEV;
+	}
+
+	ret = dfll_init_clks(td);
+	if (ret) {
+		dev_err(&pdev->dev, "DFLL clock init error\n");
+		return ret;
+	}
+
+	/* Enable the clocks and set the device up */
+	ret = dfll_init(td);
+	if (ret)
+		return ret;
+
+	ret = dfll_register_clk(td);
+	if (ret) {
+		dev_err(&pdev->dev, "DFLL clk registration failed\n");
+		return ret;
+	}
+
+#ifdef CONFIG_DEBUG_FS
+	dfll_debug_init(td);
+#endif
+
+	return 0;
+}
+EXPORT_SYMBOL(tegra_dfll_register);
+
+/**
+ * tegra_dfll_unregister - release all of the DFLL driver resources for a device
+ * @pdev: DFLL platform_device *
+ *
+ * Unbind this driver from the DFLL hardware device represented by
+ * @pdev. The DFLL must be disabled for this to succeed. Returns 0
+ * upon success or -EBUSY if the DFLL is still active.
+ */
+int tegra_dfll_unregister(struct platform_device *pdev)
+{
+	struct tegra_dfll *td = platform_get_drvdata(pdev);
+
+	/* Try to prevent removal while the DFLL is active */
+	if (td->mode != DFLL_DISABLED) {
+		dev_err(&pdev->dev,
+			"must disable DFLL before removing driver\n");
+		return -EBUSY;
+	}
+
+	debugfs_remove_recursive(td->debugfs_dir);
+
+	dfll_unregister_clk(td);
+	pm_runtime_disable(&pdev->dev);
+
+	clk_unprepare(td->ref_clk);
+	clk_unprepare(td->soc_clk);
+	clk_unprepare(td->i2c_clk);
+
+	reset_control_assert(td->dvco_rst);
+
+	return 0;
+}
+EXPORT_SYMBOL(tegra_dfll_unregister);

drivers/clk/tegra/clk-dfll.h

@@ -0,0 +1,54 @@
+/*
+ * clk-dfll.h - prototypes and macros for the Tegra DFLL clocksource driver
+ * Copyright (C) 2013 NVIDIA Corporation.  All rights reserved.
+ *
+ * Aleksandr Frid <afrid@nvidia.com>
+ * Paul Walmsley <pwalmsley@nvidia.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 program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#ifndef __DRIVERS_CLK_TEGRA_CLK_DFLL_H
+#define __DRIVERS_CLK_TEGRA_CLK_DFLL_H
+
+#include <linux/platform_device.h>
+#include <linux/reset.h>
+#include <linux/types.h>
+
+/**
+ * struct tegra_dfll_soc_data - SoC-specific hooks/integration for the DFLL driver
+ * @opp_dev: struct device * that holds the OPP table for the DFLL
+ * @min_millivolts: minimum voltage (in mV) that the DFLL can operate
+ * @tune0_low: DFLL tuning register 0 (low voltage range)
+ * @tune0_high: DFLL tuning register 0 (high voltage range)
+ * @tune1: DFLL tuning register 1
+ * @assert_dvco_reset: fn ptr to place the DVCO in reset
+ * @deassert_dvco_reset: fn ptr to release the DVCO reset
+ * @set_clock_trimmers_high: fn ptr to tune clock trimmers for high voltage
+ * @set_clock_trimmers_low: fn ptr to tune clock trimmers for low voltage
+ */
+struct tegra_dfll_soc_data {
+	struct device *opp_dev;
+	unsigned int min_millivolts;
+	u32 tune0_low;
+	u32 tune0_high;
+	u32 tune1;
+	void (*init_clock_trimmers)(void);
+	void (*set_clock_trimmers_high)(void);
+	void (*set_clock_trimmers_low)(void);
+};
+
+int tegra_dfll_register(struct platform_device *pdev,
+			struct tegra_dfll_soc_data *soc);
+int tegra_dfll_unregister(struct platform_device *pdev);
+int tegra_dfll_runtime_suspend(struct device *dev);
+int tegra_dfll_runtime_resume(struct device *dev);
+
+#endif /* __DRIVERS_CLK_TEGRA_CLK_DFLL_H */