[PATCH v2 11/12] 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: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>

---

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      | 454 +++++++++++++++++++++++++++++++++++++++
 drivers/clk/tegra/clk-tegra124.c |   4 +-
 drivers/clk/tegra/clk.h          |   2 +
 4 files changed, 460 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 f7dfb72..240e5b4 100644
--- a/drivers/clk/tegra/Makefile
+++ b/drivers/clk/tegra/Makefile
@@ -14,4 +14,4 @@ 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
diff --git a/drivers/clk/tegra/clk-emc.c b/drivers/clk/tegra/clk-emc.c
new file mode 100644
index 0000000..dcc3a5c
--- /dev/null
+++ b/drivers/clk/tegra/clk-emc.c
@@ -0,0 +1,454 @@
+/*
+ * 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/memory.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_SRC_SHIFT 29
+#define CLK_SOURCE_EMC_EMC_2X_CLK_SRC_MASK 0x7
+
+const char *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
+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_emc {
+	struct clk_hw hw;
+	void __iomem *clk_regs;
+	struct clk *prev_parent;
+	bool changing_timing;
+
+	int num_timings;
+	struct emc_timing *timings;
+};
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Common clock framework callback implementations *
+ * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+unsigned long emc_recalc_rate(struct clk_hw *hw, unsigned long parent_rate)
+{
+	struct tegra_emc *tegra = container_of(hw, struct tegra_emc, hw);
+	u32 val, div;
+
+	/* 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.
+ */
+long emc_round_rate(struct clk_hw *hw, unsigned long rate,
+		    unsigned long *parent_rate)
+{
+	struct tegra_emc *tegra = container_of(hw, struct tegra_emc, hw);
+	u8 ram_code = tegra_read_ram_code();
+	struct emc_timing *timing;
+	int i;
+
+	/* Returning the original rate will lead to a more sensible error
+	 * message when emc_set_rate fails.
+	 */
+	if (tegra->num_timings == 0)
+		return rate;
+
+	for (i = 0; i < tegra->num_timings; ++i) {
+		timing = tegra->timings + i;
+		if (timing->ram_code != ram_code)
+			continue;
+
+		if (timing->rate >= rate)
+			return timing->rate;
+	}
+
+	return tegra->timings[tegra->num_timings - 1].rate;
+}
+
+u8 emc_get_parent(struct clk_hw *hw)
+{
+	struct tegra_emc *tegra = container_of(hw, struct tegra_emc, hw);
+	u32 val;
+
+	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 int emc_set_timing(struct tegra_emc *tegra, struct emc_timing *timing)
+{
+	int err;
+	u8 div;
+	u32 car_value;
+
+	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;
+
+	car_value = 0;
+	car_value |= timing->parent_index <<
+		CLK_SOURCE_EMC_EMC_2X_CLK_SRC_SHIFT;
+	car_value |= div << CLK_SOURCE_EMC_EMC_2X_CLK_DIVISOR_SHIFT;
+
+	tegra_emc_prepare_timing_change(timing->rate);
+
+	writel(car_value, tegra->clk_regs + CLK_SOURCE_EMC);
+
+	tegra_emc_complete_timing_change(timing->rate);
+
+	__clk_reparent(tegra->hw.clk, 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_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_emc *tegra = container_of(hw, struct tegra_emc, hw);
+	struct emc_timing *timing = NULL;
+	int i, err;
+	u32 ram_code = tegra_read_ram_code();
+
+	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_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_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;
+}
+
+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)
+{
+	struct tegra_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->num_timings = 0;
+
+	for_each_child_of_node(np, node) {
+		if (strcmp(node->name, "emc-timings"))
+			continue;
+
+		err = of_property_read_u32(node, "nvidia,ram-code",
+						&node_ram_code);
+		if (err) {
+			pr_warn("skipping timing without ram-code\n");
+			continue;
+		}
+
+		err = load_timings_from_dt(tegra, node, node_ram_code);
+		if (err)
+			return ERR_PTR(err);
+		break;
+	}
+
+	if (tegra->num_timings == 0)
+		pr_warn("no memory timings registered\n");
+
+	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 07ec882..95ef153 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 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_CCLK_G, TEGRA124_CLK_CLK_MAX, 0, 1},
 	{TEGRA124_CLK_MSELECT, TEGRA124_CLK_CLK_MAX, 0, 1},
 	{TEGRA124_CLK_CSITE, TEGRA124_CLK_CLK_MAX, 0, 1},
@@ -1439,6 +1438,9 @@ static void __init tegra124_clock_init(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);
+
 	tegra_register_devclks(devclks, ARRAY_SIZE(devclks));
 
 	tegra_clk_apply_init_table = tegra124_clock_apply_init_table;
diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
index 4e458aa..f2339e8 100644
--- a/drivers/clk/tegra/clk.h
+++ b/drivers/clk/tegra/clk.h
@@ -623,6 +623,8 @@ 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);
+
 void tegra114_clock_tune_cpu_trimmers_high(void);
 void tegra114_clock_tune_cpu_trimmers_low(void);
 void tegra114_clock_tune_cpu_trimmers_init(void);
-- 
1.9.3

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