drivers/clk/tegra/clk-emc.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * drivers/clk/tegra/clk-emc.c
  *
  * Copyright (c) 2014, NVIDIA CORPORATION.  All rights reserved.
  *
  * Author:
  *	Mikko Perttunen <mperttunen@nvidia.com>
  */

 #include <linux/clk-provider.h>
 #include <linux/clk.h>
 #include <linux/clkdev.h>
 #include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/sort.h>
 #include <linux/string.h>

 #include <soc/tegra/fuse.h>
 #include <soc/tegra/emc.h>

 #include "clk.h"

 #define CLK_SOURCE_EMC 0x19c

 #define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_SHIFT 0
 #define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK 0xff
 #define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(x) (((x) & CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK) << \
 					      CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_SHIFT)

 #define CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT 29
 #define CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK 0x7
 #define CLK_SOURCE_EMC_EMC_2X_CLK_SRC(x) (((x) & CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK) << \
 					  CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT)

 static const char * const emc_parent_clk_names[] = {
 	"pll_m", "pll_c", "pll_p", "clk_m", "pll_m_ud",
 	"pll_c2", "pll_c3", "pll_c_ud"
 };

 /*
  * List of clock sources for various parents the EMC clock can have.
  * When we change the timing to a timing with a parent that has the same
  * clock source as the current parent, we must first change to a backup
  * timing that has a different clock source.
  */

 #define EMC_SRC_PLL_M 0
 #define EMC_SRC_PLL_C 1
 #define EMC_SRC_PLL_P 2
 #define EMC_SRC_CLK_M 3
 #define EMC_SRC_PLL_C2 4
 #define EMC_SRC_PLL_C3 5

 static const char emc_parent_clk_sources[] = {
 	EMC_SRC_PLL_M, EMC_SRC_PLL_C, EMC_SRC_PLL_P, EMC_SRC_CLK_M,
 	EMC_SRC_PLL_M, EMC_SRC_PLL_C2, EMC_SRC_PLL_C3, EMC_SRC_PLL_C
 };

 struct emc_timing {
 	unsigned long rate, parent_rate;
 	u8 parent_index;
 	struct clk *parent;
 	u32 ram_code;
 };

 struct tegra_clk_emc {
 	struct clk_hw hw;
 	void __iomem *clk_regs;
 	struct clk *prev_parent;
 	bool changing_timing;

 	struct device_node *emc_node;
 	struct tegra_emc *emc;

 	int num_timings;
 	struct emc_timing *timings;
 	spinlock_t *lock;
 };

 /* Common clock framework callback implementations */

 static unsigned long emc_recalc_rate(struct clk_hw *hw,
 				     unsigned long parent_rate)
 {
 	struct tegra_clk_emc *tegra;
 	u32 val, div;

 	tegra = container_of(hw, struct tegra_clk_emc, hw);

 	/*
 	 * CCF wrongly assumes that the parent won't change during set_rate,
 	 * so get the parent rate explicitly.
 	 */
 	parent_rate = clk_hw_get_rate(clk_hw_get_parent(hw));

 	val = readl(tegra->clk_regs + CLK_SOURCE_EMC);
 	div = val & CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK;

 	return parent_rate / (div + 2) * 2;
 }

 /*
  * Rounds up unless no higher rate exists, in which case down. This way is
  * safer since things have EMC rate floors. Also don't touch parent_rate
  * since we don't want the CCF to play with our parent clocks.
  */
 static int emc_determine_rate(struct clk_hw *hw, struct clk_rate_request *req)
 {
 	struct tegra_clk_emc *tegra;
 	u8 ram_code = tegra_read_ram_code();
 	struct emc_timing *timing = NULL;
 	int i, k, t;

 	tegra = container_of(hw, struct tegra_clk_emc, hw);

 	for (k = 0; k < tegra->num_timings; k++) {
 		if (tegra->timings[k].ram_code == ram_code)
 			break;
 	}

 	for (t = k; t < tegra->num_timings; t++) {
 		if (tegra->timings[t].ram_code != ram_code)
 			break;
 	}

 	for (i = k; i < t; i++) {
 		timing = tegra->timings + i;

 		if (timing->rate < req->rate && i != t - 1)
 			continue;

 		if (timing->rate > req->max_rate) {
 			i = max(i, k + 1);
 			req->rate = tegra->timings[i - 1].rate;
 			return 0;
 		}

 		if (timing->rate < req->min_rate)
 			continue;

 		req->rate = timing->rate;
 		return 0;
 	}

 	if (timing) {
 		req->rate = timing->rate;
 		return 0;
 	}

 	req->rate = clk_hw_get_rate(hw);
 	return 0;
 }

 static u8 emc_get_parent(struct clk_hw *hw)
 {
 	struct tegra_clk_emc *tegra;
 	u32 val;

 	tegra = container_of(hw, struct tegra_clk_emc, hw);

 	val = readl(tegra->clk_regs + CLK_SOURCE_EMC);

 	return (val >> CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT)
 		& CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK;
 }

 static struct tegra_emc *emc_ensure_emc_driver(struct tegra_clk_emc *tegra)
 {
 	struct platform_device *pdev;

 	if (tegra->emc)
 		return tegra->emc;

 	if (!tegra->emc_node)
 		return NULL;

 	pdev = of_find_device_by_node(tegra->emc_node);
 	if (!pdev) {
 		pr_err("%s: could not get external memory controller\n",
 		       __func__);
 		return NULL;
 	}

 	of_node_put(tegra->emc_node);
 	tegra->emc_node = NULL;

 	tegra->emc = platform_get_drvdata(pdev);
 	if (!tegra->emc) {
 		pr_err("%s: cannot find EMC driver\n", __func__);
 		return NULL;
 	}

 	return tegra->emc;
 }

 static int emc_set_timing(struct tegra_clk_emc *tegra,
 			  struct emc_timing *timing)
 {
 	int err;
 	u8 div;
 	u32 car_value;
 	unsigned long flags = 0;
 	struct tegra_emc *emc = emc_ensure_emc_driver(tegra);

 	if (!emc)
 		return -ENOENT;

 	pr_debug("going to rate %ld prate %ld p %s\n", timing->rate,
 		 timing->parent_rate, __clk_get_name(timing->parent));

 	if (emc_get_parent(&tegra->hw) == timing->parent_index &&
 	    clk_get_rate(timing->parent) != timing->parent_rate) {
 		WARN_ONCE(1, "parent %s rate mismatch %lu %lu\n",
 			  __clk_get_name(timing->parent),
 			  clk_get_rate(timing->parent),
 			  timing->parent_rate);
 		return -EINVAL;
 	}

 	tegra->changing_timing = true;

 	err = clk_set_rate(timing->parent, timing->parent_rate);
 	if (err) {
 		pr_err("cannot change parent %s rate to %ld: %d\n",
 		       __clk_get_name(timing->parent), timing->parent_rate,
 		       err);

 		return err;
 	}

 	err = clk_prepare_enable(timing->parent);
 	if (err) {
 		pr_err("cannot enable parent clock: %d\n", err);
 		return err;
 	}

 	div = timing->parent_rate / (timing->rate / 2) - 2;

 	err = tegra_emc_prepare_timing_change(emc, timing->rate);
 	if (err)
 		return err;

 	spin_lock_irqsave(tegra->lock, flags);

 	car_value = readl(tegra->clk_regs + CLK_SOURCE_EMC);

 	car_value &= ~CLK_SOURCE_EMC_EMC_2X_CLK_SRC(~0);
 	car_value |= CLK_SOURCE_EMC_EMC_2X_CLK_SRC(timing->parent_index);

 	car_value &= ~CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(~0);
 	car_value |= CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(div);

 	writel(car_value, tegra->clk_regs + CLK_SOURCE_EMC);

 	spin_unlock_irqrestore(tegra->lock, flags);

 	tegra_emc_complete_timing_change(emc, timing->rate);

 	clk_hw_reparent(&tegra->hw, __clk_get_hw(timing->parent));
 	clk_disable_unprepare(tegra->prev_parent);

 	tegra->prev_parent = timing->parent;
 	tegra->changing_timing = false;

 	return 0;
 }

 /*
  * Get backup timing to use as an intermediate step when a change between
  * two timings with the same clock source has been requested. First try to
  * find a timing with a higher clock rate to avoid a rate below any set rate
  * floors. If that is not possible, find a lower rate.
  */
 static struct emc_timing *get_backup_timing(struct tegra_clk_emc *tegra,
 					    int timing_index)
 {
 	int i;
 	u32 ram_code = tegra_read_ram_code();
 	struct emc_timing *timing;

 	for (i = timing_index+1; i < tegra->num_timings; i++) {
 		timing = tegra->timings + i;
 		if (timing->ram_code != ram_code)
 			break;

 		if (emc_parent_clk_sources[timing->parent_index] !=
 		    emc_parent_clk_sources[
 		      tegra->timings[timing_index].parent_index])
 			return timing;
 	}

 	for (i = timing_index-1; i >= 0; --i) {
 		timing = tegra->timings + i;
 		if (timing->ram_code != ram_code)
 			break;

 		if (emc_parent_clk_sources[timing->parent_index] !=
 		    emc_parent_clk_sources[
 		      tegra->timings[timing_index].parent_index])
 			return timing;
 	}

 	return NULL;
 }

 static int emc_set_rate(struct clk_hw *hw, unsigned long rate,
 			unsigned long parent_rate)
 {
 	struct tegra_clk_emc *tegra;
 	struct emc_timing *timing = NULL;
 	int i, err;
 	u32 ram_code = tegra_read_ram_code();

 	tegra = container_of(hw, struct tegra_clk_emc, hw);

 	if (clk_hw_get_rate(hw) == rate)
 		return 0;

 	/*
 	 * When emc_set_timing changes the parent rate, CCF will propagate
 	 * that downward to us, so ignore any set_rate calls while a rate
 	 * change is already going on.
 	 */
 	if (tegra->changing_timing)
 		return 0;

 	for (i = 0; i < tegra->num_timings; i++) {
 		if (tegra->timings[i].rate == rate &&
 		    tegra->timings[i].ram_code == ram_code) {
 			timing = tegra->timings + i;
 			break;
 		}
 	}

 	if (!timing) {
 		pr_err("cannot switch to rate %ld without emc table\n", rate);
 		return -EINVAL;
 	}

 	if (emc_parent_clk_sources[emc_get_parent(hw)] ==
 	    emc_parent_clk_sources[timing->parent_index] &&
 	    clk_get_rate(timing->parent) != timing->parent_rate) {
 		/*
 		 * Parent clock source not changed but parent rate has changed,
 		 * need to temporarily switch to another parent
 		 */

 		struct emc_timing *backup_timing;

 		backup_timing = get_backup_timing(tegra, i);
 		if (!backup_timing) {
 			pr_err("cannot find backup timing\n");
 			return -EINVAL;
 		}

 		pr_debug("using %ld as backup rate when going to %ld\n",
 			 backup_timing->rate, rate);

 		err = emc_set_timing(tegra, backup_timing);
 		if (err) {
 			pr_err("cannot set backup timing: %d\n", err);
 			return err;
 		}
 	}

 	return emc_set_timing(tegra, timing);
 }

 /* Initialization and deinitialization */

 static int load_one_timing_from_dt(struct tegra_clk_emc *tegra,
 				   struct emc_timing *timing,
 				   struct device_node *node)
 {
 	int err, i;
 	u32 tmp;

 	err = of_property_read_u32(node, "clock-frequency", &tmp);
 	if (err) {
 		pr_err("timing %pOF: failed to read rate\n", node);
 		return err;
 	}

 	timing->rate = tmp;

 	err = of_property_read_u32(node, "nvidia,parent-clock-frequency", &tmp);
 	if (err) {
 		pr_err("timing %pOF: failed to read parent rate\n", node);
 		return err;
 	}

 	timing->parent_rate = tmp;

 	timing->parent = of_clk_get_by_name(node, "emc-parent");
 	if (IS_ERR(timing->parent)) {
 		pr_err("timing %pOF: failed to get parent clock\n", node);
 		return PTR_ERR(timing->parent);
 	}

 	timing->parent_index = 0xff;
 	for (i = 0; i < ARRAY_SIZE(emc_parent_clk_names); i++) {
 		if (!strcmp(emc_parent_clk_names[i],
 			    __clk_get_name(timing->parent))) {
 			timing->parent_index = i;
 			break;
 		}
 	}
 	if (timing->parent_index == 0xff) {
 		pr_err("timing %pOF: %s is not a valid parent\n",
 		       node, __clk_get_name(timing->parent));
 		clk_put(timing->parent);
 		return -EINVAL;
 	}

 	return 0;
 }

 static int cmp_timings(const void *_a, const void *_b)
 {
 	const struct emc_timing *a = _a;
 	const struct emc_timing *b = _b;

 	if (a->rate < b->rate)
 		return -1;
 	else if (a->rate == b->rate)
 		return 0;
 	else
 		return 1;
 }

 static int load_timings_from_dt(struct tegra_clk_emc *tegra,
 				struct device_node *node,
 				u32 ram_code)
 {
 	struct emc_timing *timings_ptr;
 	struct device_node *child;
 	int child_count = of_get_child_count(node);
 	int i = 0, err;
 	size_t size;

 	size = (tegra->num_timings + child_count) * sizeof(struct emc_timing);

 	tegra->timings = krealloc(tegra->timings, size, GFP_KERNEL);
 	if (!tegra->timings)
 		return -ENOMEM;

 	timings_ptr = tegra->timings + tegra->num_timings;
 	tegra->num_timings += child_count;

 	for_each_child_of_node(node, child) {
 		struct emc_timing *timing = timings_ptr + (i++);

 		err = load_one_timing_from_dt(tegra, timing, child);
 		if (err) {
 			of_node_put(child);
 			return err;
 		}

 		timing->ram_code = ram_code;
 	}

 	sort(timings_ptr, child_count, sizeof(struct emc_timing),
 	     cmp_timings, NULL);

 	return 0;
 }

 static const struct clk_ops tegra_clk_emc_ops = {
 	.recalc_rate = emc_recalc_rate,
 	.determine_rate = emc_determine_rate,
 	.set_rate = emc_set_rate,
 	.get_parent = emc_get_parent,
 };

 struct clk *tegra_clk_register_emc(void __iomem *base, struct device_node *np,
 				   spinlock_t *lock)
 {
 	struct tegra_clk_emc *tegra;
 	struct clk_init_data init;
 	struct device_node *node;
 	u32 node_ram_code;
 	struct clk *clk;
 	int err;

 	tegra = kcalloc(1, sizeof(*tegra), GFP_KERNEL);
 	if (!tegra)
 		return ERR_PTR(-ENOMEM);

 	tegra->clk_regs = base;
 	tegra->lock = lock;

 	tegra->num_timings = 0;

 	for_each_child_of_node(np, node) {
 		err = of_property_read_u32(node, "nvidia,ram-code",
 					   &node_ram_code);
 		if (err)
 			continue;

 		/*
 		 * Store timings for all ram codes as we cannot read the
 		 * fuses until the apbmisc driver is loaded.
 		 */
 		err = load_timings_from_dt(tegra, node, node_ram_code);
 		if (err) {
 			of_node_put(node);
 			return ERR_PTR(err);
 		}
 	}

 	if (tegra->num_timings == 0)
 		pr_warn("%s: no memory timings registered\n", __func__);

 	tegra->emc_node = of_parse_phandle(np,
 			"nvidia,external-memory-controller", 0);
 	if (!tegra->emc_node)
 		pr_warn("%s: couldn't find node for EMC driver\n", __func__);

 	init.name = "emc";
 	init.ops = &tegra_clk_emc_ops;
 	init.flags = CLK_IS_CRITICAL;
 	init.parent_names = emc_parent_clk_names;
 	init.num_parents = ARRAY_SIZE(emc_parent_clk_names);

 	tegra->hw.init = &init;

 	clk = clk_register(NULL, &tegra->hw);
 	if (IS_ERR(clk))
 		return clk;

 	tegra->prev_parent = clk_hw_get_parent_by_index(
 		&tegra->hw, emc_get_parent(&tegra->hw))->clk;
 	tegra->changing_timing = false;

 	/* Allow debugging tools to see the EMC clock */
 	clk_register_clkdev(clk, "emc", "tegra-clk-debug");

 	return clk;
 };
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* drivers/clk/tegra/clk-emc.c
	*
	* Copyright (c) 2014, NVIDIA CORPORATION. All rights reserved.
	*
	* Author:
	* Mikko Perttunen <mperttunen@nvidia.com>
	*/

	#include <linux/clk-provider.h>
	#include <linux/clk.h>
	#include <linux/clkdev.h>
	#include <linux/delay.h>
	#include <linux/io.h>
	#include <linux/module.h>
	#include <linux/of_address.h>
	#include <linux/of_platform.h>
	#include <linux/platform_device.h>
	#include <linux/sort.h>
	#include <linux/string.h>

	#include <soc/tegra/fuse.h>
	#include <soc/tegra/emc.h>

	#include "clk.h"

	#define CLK_SOURCE_EMC 0x19c

	#define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_SHIFT 0
	#define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK 0xff
	#define CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(x) (((x) & CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK) << \
	CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_SHIFT)

	#define CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT 29
	#define CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK 0x7
	#define CLK_SOURCE_EMC_EMC_2X_CLK_SRC(x) (((x) & CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK) << \
	CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT)

	static const char * const emc_parent_clk_names[] = {
	"pll_m", "pll_c", "pll_p", "clk_m", "pll_m_ud",
	"pll_c2", "pll_c3", "pll_c_ud"
	};

	/*
	* List of clock sources for various parents the EMC clock can have.
	* When we change the timing to a timing with a parent that has the same
	* clock source as the current parent, we must first change to a backup
	* timing that has a different clock source.
	*/

	#define EMC_SRC_PLL_M 0
	#define EMC_SRC_PLL_C 1
	#define EMC_SRC_PLL_P 2
	#define EMC_SRC_CLK_M 3
	#define EMC_SRC_PLL_C2 4
	#define EMC_SRC_PLL_C3 5

	static const char emc_parent_clk_sources[] = {
	EMC_SRC_PLL_M, EMC_SRC_PLL_C, EMC_SRC_PLL_P, EMC_SRC_CLK_M,
	EMC_SRC_PLL_M, EMC_SRC_PLL_C2, EMC_SRC_PLL_C3, EMC_SRC_PLL_C
	};

	struct emc_timing {
	unsigned long rate, parent_rate;
	u8 parent_index;
	struct clk *parent;
	u32 ram_code;
	};

	struct tegra_clk_emc {
	struct clk_hw hw;
	void __iomem *clk_regs;
	struct clk *prev_parent;
	bool changing_timing;

	struct device_node *emc_node;
	struct tegra_emc *emc;

	int num_timings;
	struct emc_timing *timings;
	spinlock_t *lock;
	};

	/* Common clock framework callback implementations */

	static unsigned long emc_recalc_rate(struct clk_hw *hw,
	unsigned long parent_rate)
	{
	struct tegra_clk_emc *tegra;
	u32 val, div;

	tegra = container_of(hw, struct tegra_clk_emc, hw);

	/*
	* CCF wrongly assumes that the parent won't change during set_rate,
	* so get the parent rate explicitly.
	*/
	parent_rate = clk_hw_get_rate(clk_hw_get_parent(hw));

	val = readl(tegra->clk_regs + CLK_SOURCE_EMC);
	div = val & CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_MASK;

	return parent_rate / (div + 2) * 2;
	}

	/*
	* Rounds up unless no higher rate exists, in which case down. This way is
	* safer since things have EMC rate floors. Also don't touch parent_rate
	* since we don't want the CCF to play with our parent clocks.
	*/
	static int emc_determine_rate(struct clk_hw hw, struct clk_rate_request req)
	{
	struct tegra_clk_emc *tegra;
	u8 ram_code = tegra_read_ram_code();
	struct emc_timing *timing = NULL;
	int i, k, t;

	tegra = container_of(hw, struct tegra_clk_emc, hw);

	for (k = 0; k < tegra->num_timings; k++) {
	if (tegra->timings[k].ram_code == ram_code)
	break;
	}

	for (t = k; t < tegra->num_timings; t++) {
	if (tegra->timings[t].ram_code != ram_code)
	break;
	}

	for (i = k; i < t; i++) {
	timing = tegra->timings + i;

	if (timing->rate < req->rate && i != t - 1)
	continue;

	if (timing->rate > req->max_rate) {
	i = max(i, k + 1);
	req->rate = tegra->timings[i - 1].rate;
	return 0;
	}

	if (timing->rate < req->min_rate)
	continue;

	req->rate = timing->rate;
	return 0;
	}

	if (timing) {
	req->rate = timing->rate;
	return 0;
	}

	req->rate = clk_hw_get_rate(hw);
	return 0;
	}

	static u8 emc_get_parent(struct clk_hw *hw)
	{
	struct tegra_clk_emc *tegra;
	u32 val;

	tegra = container_of(hw, struct tegra_clk_emc, hw);

	val = readl(tegra->clk_regs + CLK_SOURCE_EMC);

	return (val >> CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT)
	& CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK;
	}

	static struct tegra_emc emc_ensure_emc_driver(struct tegra_clk_emc tegra)
	{
	struct platform_device *pdev;

	if (tegra->emc)
	return tegra->emc;

	if (!tegra->emc_node)
	return NULL;

	pdev = of_find_device_by_node(tegra->emc_node);
	if (!pdev) {
	pr_err("%s: could not get external memory controller\n",
	__func__);
	return NULL;
	}

	of_node_put(tegra->emc_node);
	tegra->emc_node = NULL;

	tegra->emc = platform_get_drvdata(pdev);
	if (!tegra->emc) {
	pr_err("%s: cannot find EMC driver\n", __func__);
	return NULL;
	}

	return tegra->emc;
	}

	static int emc_set_timing(struct tegra_clk_emc *tegra,
	struct emc_timing *timing)
	{
	int err;
	u8 div;
	u32 car_value;
	unsigned long flags = 0;
	struct tegra_emc *emc = emc_ensure_emc_driver(tegra);

	if (!emc)
	return -ENOENT;

	pr_debug("going to rate %ld prate %ld p %s\n", timing->rate,
	timing->parent_rate, __clk_get_name(timing->parent));

	if (emc_get_parent(&tegra->hw) == timing->parent_index &&
	clk_get_rate(timing->parent) != timing->parent_rate) {
	WARN_ONCE(1, "parent %s rate mismatch %lu %lu\n",
	__clk_get_name(timing->parent),
	clk_get_rate(timing->parent),
	timing->parent_rate);
	return -EINVAL;
	}

	tegra->changing_timing = true;

	err = clk_set_rate(timing->parent, timing->parent_rate);
	if (err) {
	pr_err("cannot change parent %s rate to %ld: %d\n",
	__clk_get_name(timing->parent), timing->parent_rate,
	err);

	return err;
	}

	err = clk_prepare_enable(timing->parent);
	if (err) {
	pr_err("cannot enable parent clock: %d\n", err);
	return err;
	}

	div = timing->parent_rate / (timing->rate / 2) - 2;

	err = tegra_emc_prepare_timing_change(emc, timing->rate);
	if (err)
	return err;

	spin_lock_irqsave(tegra->lock, flags);

	car_value = readl(tegra->clk_regs + CLK_SOURCE_EMC);

	car_value &= ~CLK_SOURCE_EMC_EMC_2X_CLK_SRC(~0);
	car_value \|= CLK_SOURCE_EMC_EMC_2X_CLK_SRC(timing->parent_index);

	car_value &= ~CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(~0);
	car_value \|= CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR(div);

	writel(car_value, tegra->clk_regs + CLK_SOURCE_EMC);

	spin_unlock_irqrestore(tegra->lock, flags);

	tegra_emc_complete_timing_change(emc, timing->rate);

	clk_hw_reparent(&tegra->hw, __clk_get_hw(timing->parent));
	clk_disable_unprepare(tegra->prev_parent);

	tegra->prev_parent = timing->parent;
	tegra->changing_timing = false;

	return 0;
	}

	/*
	* Get backup timing to use as an intermediate step when a change between
	* two timings with the same clock source has been requested. First try to
	* find a timing with a higher clock rate to avoid a rate below any set rate
	* floors. If that is not possible, find a lower rate.
	*/
	static struct emc_timing get_backup_timing(struct tegra_clk_emc tegra,
	int timing_index)
	{
	int i;
	u32 ram_code = tegra_read_ram_code();
	struct emc_timing *timing;

	for (i = timing_index+1; i < tegra->num_timings; i++) {
	timing = tegra->timings + i;
	if (timing->ram_code != ram_code)
	break;

	if (emc_parent_clk_sources[timing->parent_index] !=
	emc_parent_clk_sources[
	tegra->timings[timing_index].parent_index])
	return timing;
	}

	for (i = timing_index-1; i >= 0; --i) {
	timing = tegra->timings + i;
	if (timing->ram_code != ram_code)
	break;

	if (emc_parent_clk_sources[timing->parent_index] !=
	emc_parent_clk_sources[
	tegra->timings[timing_index].parent_index])
	return timing;
	}

	return NULL;
	}

	static int emc_set_rate(struct clk_hw *hw, unsigned long rate,
	unsigned long parent_rate)
	{
	struct tegra_clk_emc *tegra;
	struct emc_timing *timing = NULL;
	int i, err;
	u32 ram_code = tegra_read_ram_code();

	tegra = container_of(hw, struct tegra_clk_emc, hw);

	if (clk_hw_get_rate(hw) == rate)
	return 0;

	/*
	* When emc_set_timing changes the parent rate, CCF will propagate
	* that downward to us, so ignore any set_rate calls while a rate
	* change is already going on.
	*/
	if (tegra->changing_timing)
	return 0;

	for (i = 0; i < tegra->num_timings; i++) {
	if (tegra->timings[i].rate == rate &&
	tegra->timings[i].ram_code == ram_code) {
	timing = tegra->timings + i;
	break;
	}
	}

	if (!timing) {
	pr_err("cannot switch to rate %ld without emc table\n", rate);
	return -EINVAL;
	}

	if (emc_parent_clk_sources[emc_get_parent(hw)] ==
	emc_parent_clk_sources[timing->parent_index] &&
	clk_get_rate(timing->parent) != timing->parent_rate) {
	/*
	* Parent clock source not changed but parent rate has changed,
	* need to temporarily switch to another parent
	*/

	struct emc_timing *backup_timing;

	backup_timing = get_backup_timing(tegra, i);
	if (!backup_timing) {
	pr_err("cannot find backup timing\n");
	return -EINVAL;
	}

	pr_debug("using %ld as backup rate when going to %ld\n",
	backup_timing->rate, rate);

	err = emc_set_timing(tegra, backup_timing);
	if (err) {
	pr_err("cannot set backup timing: %d\n", err);
	return err;
	}
	}

	return emc_set_timing(tegra, timing);
	}

	/* Initialization and deinitialization */

	static int load_one_timing_from_dt(struct tegra_clk_emc *tegra,
	struct emc_timing *timing,
	struct device_node *node)
	{
	int err, i;
	u32 tmp;

	err = of_property_read_u32(node, "clock-frequency", &tmp);
	if (err) {
	pr_err("timing %pOF: failed to read rate\n", node);
	return err;
	}

	timing->rate = tmp;

	err = of_property_read_u32(node, "nvidia,parent-clock-frequency", &tmp);
	if (err) {
	pr_err("timing %pOF: failed to read parent rate\n", node);
	return err;
	}

	timing->parent_rate = tmp;

	timing->parent = of_clk_get_by_name(node, "emc-parent");
	if (IS_ERR(timing->parent)) {
	pr_err("timing %pOF: failed to get parent clock\n", node);
	return PTR_ERR(timing->parent);
	}

	timing->parent_index = 0xff;
	for (i = 0; i < ARRAY_SIZE(emc_parent_clk_names); i++) {
	if (!strcmp(emc_parent_clk_names[i],
	__clk_get_name(timing->parent))) {
	timing->parent_index = i;
	break;
	}
	}
	if (timing->parent_index == 0xff) {
	pr_err("timing %pOF: %s is not a valid parent\n",
	node, __clk_get_name(timing->parent));
	clk_put(timing->parent);
	return -EINVAL;
	}

	return 0;
	}

	static int cmp_timings(const void _a, const void _b)
	{
	const struct emc_timing *a = _a;
	const struct emc_timing *b = _b;

	if (a->rate < b->rate)
	return -1;
	else if (a->rate == b->rate)
	return 0;
	else
	return 1;
	}

	static int load_timings_from_dt(struct tegra_clk_emc *tegra,
	struct device_node *node,
	u32 ram_code)
	{
	struct emc_timing *timings_ptr;
	struct device_node *child;
	int child_count = of_get_child_count(node);
	int i = 0, err;
	size_t size;

	size = (tegra->num_timings + child_count) * sizeof(struct emc_timing);

	tegra->timings = krealloc(tegra->timings, size, GFP_KERNEL);
	if (!tegra->timings)
	return -ENOMEM;

	timings_ptr = tegra->timings + tegra->num_timings;
	tegra->num_timings += child_count;

	for_each_child_of_node(node, child) {
	struct emc_timing *timing = timings_ptr + (i++);

	err = load_one_timing_from_dt(tegra, timing, child);
	if (err) {
	of_node_put(child);
	return err;
	}

	timing->ram_code = ram_code;
	}

	sort(timings_ptr, child_count, sizeof(struct emc_timing),
	cmp_timings, NULL);

	return 0;
	}

	static const struct clk_ops tegra_clk_emc_ops = {
	.recalc_rate = emc_recalc_rate,
	.determine_rate = emc_determine_rate,
	.set_rate = emc_set_rate,
	.get_parent = emc_get_parent,
	};

	struct clk tegra_clk_register_emc(void __iomem base, struct device_node *np,
	spinlock_t *lock)
	{
	struct tegra_clk_emc *tegra;
	struct clk_init_data init;
	struct device_node *node;
	u32 node_ram_code;
	struct clk *clk;
	int err;

	tegra = kcalloc(1, sizeof(*tegra), GFP_KERNEL);
	if (!tegra)
	return ERR_PTR(-ENOMEM);

	tegra->clk_regs = base;
	tegra->lock = lock;

	tegra->num_timings = 0;

	for_each_child_of_node(np, node) {
	err = of_property_read_u32(node, "nvidia,ram-code",
	&node_ram_code);
	if (err)
	continue;

	/*
	* Store timings for all ram codes as we cannot read the
	* fuses until the apbmisc driver is loaded.
	*/
	err = load_timings_from_dt(tegra, node, node_ram_code);
	if (err) {
	of_node_put(node);
	return ERR_PTR(err);
	}
	}

	if (tegra->num_timings == 0)
	pr_warn("%s: no memory timings registered\n", __func__);

	tegra->emc_node = of_parse_phandle(np,
	"nvidia,external-memory-controller", 0);
	if (!tegra->emc_node)
	pr_warn("%s: couldn't find node for EMC driver\n", __func__);

	init.name = "emc";
	init.ops = &tegra_clk_emc_ops;
	init.flags = CLK_IS_CRITICAL;
	init.parent_names = emc_parent_clk_names;
	init.num_parents = ARRAY_SIZE(emc_parent_clk_names);

	tegra->hw.init = &init;

	clk = clk_register(NULL, &tegra->hw);
	if (IS_ERR(clk))
	return clk;

	tegra->prev_parent = clk_hw_get_parent_by_index(
	&tegra->hw, emc_get_parent(&tegra->hw))->clk;
	tegra->changing_timing = false;

	/* Allow debugging tools to see the EMC clock */
	clk_register_clkdev(clk, "emc", "tegra-clk-debug");

	return clk;
	};