[PATCH v8 13/18] clk: tegra: Add EMC clock driver

[Tomeu Vizoso]

From: Mikko Perttunen <mperttunen@xxxxxxxxxx>

The driver is currently only tested on Tegra124 Jetson TK1, but should
work with other Tegra124 boards, provided that correct EMC tables are
provided through the device tree. Older chip models have differing
timing change sequences, so they are not currently supported.

Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>

---

v6:	* Rebase
	* Use clk_hw_reparent as __clk_reparent isn't any more
	* Simplify emc_round_rate a bit

v5:	* Get a pointer to the EMC driver at runtime, to be used when
	  calling the EMC API.
	* Misc. style fixes
	* Fix logic for rounding down to a high rate

v4:	* Adapt to changes in the OF bindings
	* Improve error handling
	* Fix comment style
	* Make static a few more functions

v3:	* Add some locking to protect the registers that are shared with the MC
	  clock

v2:	* Make sure that the clock is properly registered
	* Bail out early from attempts to set the same rate
---
 drivers/clk/tegra/Makefile       |   2 +-
 drivers/clk/tegra/clk-emc.c      | 528 +++++++++++++++++++++++++++++++++++++++
 drivers/clk/tegra/clk-tegra124.c |   4 +-
 drivers/clk/tegra/clk.h          |   3 +
 4 files changed, 535 insertions(+), 2 deletions(-)
 create mode 100644 drivers/clk/tegra/clk-emc.c

diff --git a/drivers/clk/tegra/Makefile b/drivers/clk/tegra/Makefile
index edb8358..18c28d1 100644
--- a/drivers/clk/tegra/Makefile
+++ b/drivers/clk/tegra/Makefile
@@ -14,5 +14,5 @@ obj-y					+= clk-tegra-super-gen4.o
 obj-$(CONFIG_ARCH_TEGRA_2x_SOC)         += clk-tegra20.o
 obj-$(CONFIG_ARCH_TEGRA_3x_SOC)         += clk-tegra30.o
 obj-$(CONFIG_ARCH_TEGRA_114_SOC)	+= clk-tegra114.o
-obj-$(CONFIG_ARCH_TEGRA_124_SOC)	+= clk-tegra124.o
+obj-$(CONFIG_ARCH_TEGRA_124_SOC)	+= clk-tegra124.o clk-emc.o
 obj-$(CONFIG_ARCH_TEGRA_132_SOC)	+= clk-tegra124.o
diff --git a/drivers/clk/tegra/clk-emc.c b/drivers/clk/tegra/clk-emc.c
new file mode 100644
index 0000000..704fff7
--- /dev/null
+++ b/drivers/clk/tegra/clk-emc.c
@@ -0,0 +1,528 @@
+/*
+ * drivers/clk/tegra/clk-emc.c
+ *
+ * Copyright (c) 2014, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * Author:
+ *	Mikko Perttunen <mperttunen@xxxxxxxxxx>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * 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.
+ *
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/delay.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_get_rate(__clk_get_parent(hw->clk));
+
+	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 long emc_round_rate(struct clk_hw *hw, unsigned long rate,
+		    unsigned long *parent_rate)
+{
+	struct tegra_clk_emc *tegra;
+	u8 ram_code = tegra_read_ram_code();
+	struct emc_timing *timing = NULL;
+	int i;
+
+	tegra = container_of(hw, struct tegra_clk_emc, hw);
+
+         for (i = 0; i < tegra->num_timings; i++) {
+                if (tegra->timings[i].ram_code != ram_code)
+                        continue;
+
+                timing = tegra->timings + i;
+
+                if (timing->rate >= rate)
+                        return timing->rate;
+        }
+
+        if (timing)
+                return timing->rate;
+
+	return __clk_get_rate(hw->clk);
+}
+
+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) {
+		BUG();
+		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)
+			continue;
+
+		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)
+			continue;
+
+		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_get_rate(hw->clk) == 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 %s: failed to read rate\n", node->full_name);
+		return err;
+	}
+
+	timing->rate = tmp;
+
+	err = of_property_read_u32(node, "nvidia,parent-clock-frequency", &tmp);
+	if (err) {
+		pr_err("timing %s: failed to read parent rate\n",
+		       node->full_name);
+		return err;
+	}
+
+	timing->parent_rate = tmp;
+
+	timing->parent = of_clk_get_by_name(node, "emc-parent");
+	if (IS_ERR(timing->parent)) {
+		pr_err("timing %s: failed to get parent clock\n",
+		       node->full_name);
+		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 %s: %s is not a valid parent\n",
+		       node->full_name, __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 device_node *child;
+	int child_count = of_get_child_count(node);
+	int i = 0, err;
+
+	tegra->timings = kcalloc(child_count, sizeof(struct emc_timing),
+				 GFP_KERNEL);
+	if (!tegra->timings)
+		return -ENOMEM;
+
+	tegra->num_timings = child_count;
+
+	for_each_child_of_node(node, child) {
+		struct emc_timing *timing = tegra->timings + (i++);
+
+		err = load_one_timing_from_dt(tegra, timing, child);
+		if (err)
+			return err;
+
+		timing->ram_code = ram_code;
+	}
+
+	sort(tegra->timings, tegra->num_timings, sizeof(struct emc_timing),
+	     cmp_timings, NULL);
+
+	return 0;
+}
+
+static const struct clk_ops tegra_clk_emc_ops = {
+	.recalc_rate = emc_recalc_rate,
+	.round_rate = emc_round_rate,
+	.set_rate = emc_set_rate,
+	.get_parent = emc_get_parent,
+};
+
+struct clk *tegra_emc_init(struct device_node *np, void __iomem *clk_regs,
+			   spinlock_t *lock)
+{
+	struct tegra_clk_emc *tegra;
+	struct clk *clk;
+	struct clk_init_data init;
+	struct device_node *node;
+	u32 node_ram_code;
+	int err;
+
+	tegra = kcalloc(1, sizeof(*tegra), GFP_KERNEL);
+	if (!tegra)
+		return ERR_PTR(-ENOMEM);
+
+	tegra->clk_regs = clk_regs;
+	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) {
+			of_node_put(node);
+			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)
+			return ERR_PTR(err);
+		of_node_put(node);
+		break;
+	}
+
+	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 = 0;
+	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_get_parent_by_index(
+		tegra->hw.clk, emc_get_parent(&tegra->hw));
+	tegra->changing_timing = false;
+
+	/* Allow debugging tools to see the EMC clock */
+	clk_register_clkdev(clk, "emc", "tegra-clk-debug");
+
+	clk_prepare_enable(clk);
+
+	return clk;
+};
diff --git a/drivers/clk/tegra/clk-tegra124.c b/drivers/clk/tegra/clk-tegra124.c
index d370134..8a813c4 100644
--- a/drivers/clk/tegra/clk-tegra124.c
+++ b/drivers/clk/tegra/clk-tegra124.c
@@ -1383,7 +1383,6 @@ static struct tegra_clk_init_table common_init_table[] __initdata = {
 	{TEGRA124_CLK_XUSB_HOST_SRC, TEGRA124_CLK_PLL_RE_OUT, 112000000, 0},
 	{TEGRA124_CLK_SATA, TEGRA124_CLK_PLL_P, 104000000, 0},
 	{TEGRA124_CLK_SATA_OOB, TEGRA124_CLK_PLL_P, 204000000, 0},
-	{TEGRA124_CLK_EMC, TEGRA124_CLK_CLK_MAX, 0, 1},
 	{TEGRA124_CLK_MSELECT, TEGRA124_CLK_CLK_MAX, 0, 1},
 	{TEGRA124_CLK_CSITE, TEGRA124_CLK_CLK_MAX, 0, 1},
 	{TEGRA124_CLK_TSENSOR, TEGRA124_CLK_CLK_M, 400000, 0},
@@ -1504,6 +1503,9 @@ static void __init tegra124_132_clock_init_post(struct device_node *np)
 	tegra_super_clk_gen4_init(clk_base, pmc_base, tegra124_clks,
 				  &pll_x_params);
 	tegra_add_of_provider(np);
+
+	clks[TEGRA124_CLK_EMC] = tegra_emc_init(np, clk_base, &emc_lock);
+
 	tegra_register_devclks(devclks, ARRAY_SIZE(devclks));
 
 	tegra_cpu_car_ops = &tegra124_cpu_car_ops;
diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
index 4e458aa..097f972 100644
--- a/drivers/clk/tegra/clk.h
+++ b/drivers/clk/tegra/clk.h
@@ -623,6 +623,9 @@ void tegra_super_clk_gen4_init(void __iomem *clk_base,
 			void __iomem *pmc_base, struct tegra_clk *tegra_clks,
 			struct tegra_clk_pll_params *pll_params);
 
+struct clk *tegra_emc_init(struct device_node *np, void __iomem *clk_regs,
+			   spinlock_t *lock);
+
 void tegra114_clock_tune_cpu_trimmers_high(void);
 void tegra114_clock_tune_cpu_trimmers_low(void);
 void tegra114_clock_tune_cpu_trimmers_init(void);
-- 
2.1.0

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