Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1279 insertions, 0 deletions

diff --git a/drivers/memory/tegra/tegra20-emc.c b/drivers/memory/tegra/tegra20-emc.c
new file mode 100644
index 0000000000..fd595c851a
--- /dev/null
+++ b/drivers/memory/tegra/tegra20-emc.c
@@ -0,0 +1,1279 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Tegra20 External Memory Controller driver
+ *
+ * Author: Dmitry Osipenko <digetx@gmail.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/clk/tegra.h>
+#include <linux/debugfs.h>
+#include <linux/devfreq.h>
+#include <linux/err.h>
+#include <linux/interconnect-provider.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+#include <linux/types.h>
+
+#include <soc/tegra/common.h>
+#include <soc/tegra/fuse.h>
+
+#include "../jedec_ddr.h"
+#include "../of_memory.h"
+
+#include "mc.h"
+
+#define EMC_INTSTATUS				0x000
+#define EMC_INTMASK				0x004
+#define EMC_DBG					0x008
+#define EMC_ADR_CFG_0				0x010
+#define EMC_TIMING_CONTROL			0x028
+#define EMC_RC					0x02c
+#define EMC_RFC					0x030
+#define EMC_RAS					0x034
+#define EMC_RP					0x038
+#define EMC_R2W					0x03c
+#define EMC_W2R					0x040
+#define EMC_R2P					0x044
+#define EMC_W2P					0x048
+#define EMC_RD_RCD				0x04c
+#define EMC_WR_RCD				0x050
+#define EMC_RRD					0x054
+#define EMC_REXT				0x058
+#define EMC_WDV					0x05c
+#define EMC_QUSE				0x060
+#define EMC_QRST				0x064
+#define EMC_QSAFE				0x068
+#define EMC_RDV					0x06c
+#define EMC_REFRESH				0x070
+#define EMC_BURST_REFRESH_NUM			0x074
+#define EMC_PDEX2WR				0x078
+#define EMC_PDEX2RD				0x07c
+#define EMC_PCHG2PDEN				0x080
+#define EMC_ACT2PDEN				0x084
+#define EMC_AR2PDEN				0x088
+#define EMC_RW2PDEN				0x08c
+#define EMC_TXSR				0x090
+#define EMC_TCKE				0x094
+#define EMC_TFAW				0x098
+#define EMC_TRPAB				0x09c
+#define EMC_TCLKSTABLE				0x0a0
+#define EMC_TCLKSTOP				0x0a4
+#define EMC_TREFBW				0x0a8
+#define EMC_QUSE_EXTRA				0x0ac
+#define EMC_ODT_WRITE				0x0b0
+#define EMC_ODT_READ				0x0b4
+#define EMC_MRR					0x0ec
+#define EMC_FBIO_CFG5				0x104
+#define EMC_FBIO_CFG6				0x114
+#define EMC_STAT_CONTROL			0x160
+#define EMC_STAT_LLMC_CONTROL			0x178
+#define EMC_STAT_PWR_CLOCK_LIMIT		0x198
+#define EMC_STAT_PWR_CLOCKS			0x19c
+#define EMC_STAT_PWR_COUNT			0x1a0
+#define EMC_AUTO_CAL_INTERVAL			0x2a8
+#define EMC_CFG_2				0x2b8
+#define EMC_CFG_DIG_DLL				0x2bc
+#define EMC_DLL_XFORM_DQS			0x2c0
+#define EMC_DLL_XFORM_QUSE			0x2c4
+#define EMC_ZCAL_REF_CNT			0x2e0
+#define EMC_ZCAL_WAIT_CNT			0x2e4
+#define EMC_CFG_CLKTRIM_0			0x2d0
+#define EMC_CFG_CLKTRIM_1			0x2d4
+#define EMC_CFG_CLKTRIM_2			0x2d8
+
+#define EMC_CLKCHANGE_REQ_ENABLE		BIT(0)
+#define EMC_CLKCHANGE_PD_ENABLE			BIT(1)
+#define EMC_CLKCHANGE_SR_ENABLE			BIT(2)
+
+#define EMC_TIMING_UPDATE			BIT(0)
+
+#define EMC_REFRESH_OVERFLOW_INT		BIT(3)
+#define EMC_CLKCHANGE_COMPLETE_INT		BIT(4)
+#define EMC_MRR_DIVLD_INT			BIT(5)
+
+#define EMC_DBG_READ_MUX_ASSEMBLY		BIT(0)
+#define EMC_DBG_WRITE_MUX_ACTIVE		BIT(1)
+#define EMC_DBG_FORCE_UPDATE			BIT(2)
+#define EMC_DBG_READ_DQM_CTRL			BIT(9)
+#define EMC_DBG_CFG_PRIORITY			BIT(24)
+
+#define EMC_FBIO_CFG5_DRAM_WIDTH_X16		BIT(4)
+#define EMC_FBIO_CFG5_DRAM_TYPE			GENMASK(1, 0)
+
+#define EMC_MRR_DEV_SELECTN			GENMASK(31, 30)
+#define EMC_MRR_MRR_MA				GENMASK(23, 16)
+#define EMC_MRR_MRR_DATA			GENMASK(15, 0)
+
+#define EMC_ADR_CFG_0_EMEM_NUMDEV		GENMASK(25, 24)
+
+#define EMC_PWR_GATHER_CLEAR			(1 << 8)
+#define EMC_PWR_GATHER_DISABLE			(2 << 8)
+#define EMC_PWR_GATHER_ENABLE			(3 << 8)
+
+enum emc_dram_type {
+	DRAM_TYPE_RESERVED,
+	DRAM_TYPE_DDR1,
+	DRAM_TYPE_LPDDR2,
+	DRAM_TYPE_DDR2,
+};
+
+static const u16 emc_timing_registers[] = {
+	EMC_RC,
+	EMC_RFC,
+	EMC_RAS,
+	EMC_RP,
+	EMC_R2W,
+	EMC_W2R,
+	EMC_R2P,
+	EMC_W2P,
+	EMC_RD_RCD,
+	EMC_WR_RCD,
+	EMC_RRD,
+	EMC_REXT,
+	EMC_WDV,
+	EMC_QUSE,
+	EMC_QRST,
+	EMC_QSAFE,
+	EMC_RDV,
+	EMC_REFRESH,
+	EMC_BURST_REFRESH_NUM,
+	EMC_PDEX2WR,
+	EMC_PDEX2RD,
+	EMC_PCHG2PDEN,
+	EMC_ACT2PDEN,
+	EMC_AR2PDEN,
+	EMC_RW2PDEN,
+	EMC_TXSR,
+	EMC_TCKE,
+	EMC_TFAW,
+	EMC_TRPAB,
+	EMC_TCLKSTABLE,
+	EMC_TCLKSTOP,
+	EMC_TREFBW,
+	EMC_QUSE_EXTRA,
+	EMC_FBIO_CFG6,
+	EMC_ODT_WRITE,
+	EMC_ODT_READ,
+	EMC_FBIO_CFG5,
+	EMC_CFG_DIG_DLL,
+	EMC_DLL_XFORM_DQS,
+	EMC_DLL_XFORM_QUSE,
+	EMC_ZCAL_REF_CNT,
+	EMC_ZCAL_WAIT_CNT,
+	EMC_AUTO_CAL_INTERVAL,
+	EMC_CFG_CLKTRIM_0,
+	EMC_CFG_CLKTRIM_1,
+	EMC_CFG_CLKTRIM_2,
+};
+
+struct emc_timing {
+	unsigned long rate;
+	u32 data[ARRAY_SIZE(emc_timing_registers)];
+};
+
+enum emc_rate_request_type {
+	EMC_RATE_DEVFREQ,
+	EMC_RATE_DEBUG,
+	EMC_RATE_ICC,
+	EMC_RATE_TYPE_MAX,
+};
+
+struct emc_rate_request {
+	unsigned long min_rate;
+	unsigned long max_rate;
+};
+
+struct tegra_emc {
+	struct device *dev;
+	struct tegra_mc *mc;
+	struct icc_provider provider;
+	struct notifier_block clk_nb;
+	struct clk *clk;
+	void __iomem *regs;
+	unsigned int dram_bus_width;
+
+	struct emc_timing *timings;
+	unsigned int num_timings;
+
+	struct {
+		struct dentry *root;
+		unsigned long min_rate;
+		unsigned long max_rate;
+	} debugfs;
+
+	/*
+	 * There are multiple sources in the EMC driver which could request
+	 * a min/max clock rate, these rates are contained in this array.
+	 */
+	struct emc_rate_request requested_rate[EMC_RATE_TYPE_MAX];
+
+	/* protect shared rate-change code path */
+	struct mutex rate_lock;
+
+	struct devfreq_simple_ondemand_data ondemand_data;
+
+	/* memory chip identity information */
+	union lpddr2_basic_config4 basic_conf4;
+	unsigned int manufacturer_id;
+	unsigned int revision_id1;
+	unsigned int revision_id2;
+
+	bool mrr_error;
+};
+
+static irqreturn_t tegra_emc_isr(int irq, void *data)
+{
+	struct tegra_emc *emc = data;
+	u32 intmask = EMC_REFRESH_OVERFLOW_INT;
+	u32 status;
+
+	status = readl_relaxed(emc->regs + EMC_INTSTATUS) & intmask;
+	if (!status)
+		return IRQ_NONE;
+
+	/* notify about HW problem */
+	if (status & EMC_REFRESH_OVERFLOW_INT)
+		dev_err_ratelimited(emc->dev,
+				    "refresh request overflow timeout\n");
+
+	/* clear interrupts */
+	writel_relaxed(status, emc->regs + EMC_INTSTATUS);
+
+	return IRQ_HANDLED;
+}
+
+static struct emc_timing *tegra_emc_find_timing(struct tegra_emc *emc,
+						unsigned long rate)
+{
+	struct emc_timing *timing = NULL;
+	unsigned int i;
+
+	for (i = 0; i < emc->num_timings; i++) {
+		if (emc->timings[i].rate >= rate) {
+			timing = &emc->timings[i];
+			break;
+		}
+	}
+
+	if (!timing) {
+		dev_err(emc->dev, "no timing for rate %lu\n", rate);
+		return NULL;
+	}
+
+	return timing;
+}
+
+static int emc_prepare_timing_change(struct tegra_emc *emc, unsigned long rate)
+{
+	struct emc_timing *timing = tegra_emc_find_timing(emc, rate);
+	unsigned int i;
+
+	if (!timing)
+		return -EINVAL;
+
+	dev_dbg(emc->dev, "%s: using timing rate %lu for requested rate %lu\n",
+		__func__, timing->rate, rate);
+
+	/* program shadow registers */
+	for (i = 0; i < ARRAY_SIZE(timing->data); i++)
+		writel_relaxed(timing->data[i],
+			       emc->regs + emc_timing_registers[i]);
+
+	/* wait until programming has settled */
+	readl_relaxed(emc->regs + emc_timing_registers[i - 1]);
+
+	return 0;
+}
+
+static int emc_complete_timing_change(struct tegra_emc *emc, bool flush)
+{
+	int err;
+	u32 v;
+
+	dev_dbg(emc->dev, "%s: flush %d\n", __func__, flush);
+
+	if (flush) {
+		/* manually initiate memory timing update */
+		writel_relaxed(EMC_TIMING_UPDATE,
+			       emc->regs + EMC_TIMING_CONTROL);
+		return 0;
+	}
+
+	err = readl_relaxed_poll_timeout_atomic(emc->regs + EMC_INTSTATUS, v,
+						v & EMC_CLKCHANGE_COMPLETE_INT,
+						1, 100);
+	if (err) {
+		dev_err(emc->dev, "emc-car handshake timeout: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static int tegra_emc_clk_change_notify(struct notifier_block *nb,
+				       unsigned long msg, void *data)
+{
+	struct tegra_emc *emc = container_of(nb, struct tegra_emc, clk_nb);
+	struct clk_notifier_data *cnd = data;
+	int err;
+
+	switch (msg) {
+	case PRE_RATE_CHANGE:
+		err = emc_prepare_timing_change(emc, cnd->new_rate);
+		break;
+
+	case ABORT_RATE_CHANGE:
+		err = emc_prepare_timing_change(emc, cnd->old_rate);
+		if (err)
+			break;
+
+		err = emc_complete_timing_change(emc, true);
+		break;
+
+	case POST_RATE_CHANGE:
+		err = emc_complete_timing_change(emc, false);
+		break;
+
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return notifier_from_errno(err);
+}
+
+static int load_one_timing_from_dt(struct tegra_emc *emc,
+				   struct emc_timing *timing,
+				   struct device_node *node)
+{
+	u32 rate;
+	int err;
+
+	if (!of_device_is_compatible(node, "nvidia,tegra20-emc-table")) {
+		dev_err(emc->dev, "incompatible DT node: %pOF\n", node);
+		return -EINVAL;
+	}
+
+	err = of_property_read_u32(node, "clock-frequency", &rate);
+	if (err) {
+		dev_err(emc->dev, "timing %pOF: failed to read rate: %d\n",
+			node, err);
+		return err;
+	}
+
+	err = of_property_read_u32_array(node, "nvidia,emc-registers",
+					 timing->data,
+					 ARRAY_SIZE(emc_timing_registers));
+	if (err) {
+		dev_err(emc->dev,
+			"timing %pOF: failed to read emc timing data: %d\n",
+			node, err);
+		return err;
+	}
+
+	/*
+	 * The EMC clock rate is twice the bus rate, and the bus rate is
+	 * measured in kHz.
+	 */
+	timing->rate = rate * 2 * 1000;
+
+	dev_dbg(emc->dev, "%s: %pOF: EMC rate %lu\n",
+		__func__, node, timing->rate);
+
+	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;
+
+	if (a->rate > b->rate)
+		return 1;
+
+	return 0;
+}
+
+static int tegra_emc_load_timings_from_dt(struct tegra_emc *emc,
+					  struct device_node *node)
+{
+	struct device_node *child;
+	struct emc_timing *timing;
+	int child_count;
+	int err;
+
+	child_count = of_get_child_count(node);
+	if (!child_count) {
+		dev_err(emc->dev, "no memory timings in DT node: %pOF\n", node);
+		return -EINVAL;
+	}
+
+	emc->timings = devm_kcalloc(emc->dev, child_count, sizeof(*timing),
+				    GFP_KERNEL);
+	if (!emc->timings)
+		return -ENOMEM;
+
+	timing = emc->timings;
+
+	for_each_child_of_node(node, child) {
+		if (of_node_name_eq(child, "lpddr2"))
+			continue;
+
+		err = load_one_timing_from_dt(emc, timing++, child);
+		if (err) {
+			of_node_put(child);
+			return err;
+		}
+
+		emc->num_timings++;
+	}
+
+	sort(emc->timings, emc->num_timings, sizeof(*timing), cmp_timings,
+	     NULL);
+
+	dev_info_once(emc->dev,
+		      "got %u timings for RAM code %u (min %luMHz max %luMHz)\n",
+		      emc->num_timings,
+		      tegra_read_ram_code(),
+		      emc->timings[0].rate / 1000000,
+		      emc->timings[emc->num_timings - 1].rate / 1000000);
+
+	return 0;
+}
+
+static struct device_node *
+tegra_emc_find_node_by_ram_code(struct tegra_emc *emc)
+{
+	struct device *dev = emc->dev;
+	struct device_node *np;
+	u32 value, ram_code;
+	int err;
+
+	if (emc->mrr_error) {
+		dev_warn(dev, "memory timings skipped due to MRR error\n");
+		return NULL;
+	}
+
+	if (of_get_child_count(dev->of_node) == 0) {
+		dev_info_once(dev, "device-tree doesn't have memory timings\n");
+		return NULL;
+	}
+
+	if (!of_property_read_bool(dev->of_node, "nvidia,use-ram-code"))
+		return of_node_get(dev->of_node);
+
+	ram_code = tegra_read_ram_code();
+
+	for (np = of_find_node_by_name(dev->of_node, "emc-tables"); np;
+	     np = of_find_node_by_name(np, "emc-tables")) {
+		err = of_property_read_u32(np, "nvidia,ram-code", &value);
+		if (err || value != ram_code) {
+			struct device_node *lpddr2_np;
+			bool cfg_mismatches = false;
+
+			lpddr2_np = of_find_node_by_name(np, "lpddr2");
+			if (lpddr2_np) {
+				const struct lpddr2_info *info;
+
+				info = of_lpddr2_get_info(lpddr2_np, dev);
+				if (info) {
+					if (info->manufacturer_id >= 0 &&
+					    info->manufacturer_id != emc->manufacturer_id)
+						cfg_mismatches = true;
+
+					if (info->revision_id1 >= 0 &&
+					    info->revision_id1 != emc->revision_id1)
+						cfg_mismatches = true;
+
+					if (info->revision_id2 >= 0 &&
+					    info->revision_id2 != emc->revision_id2)
+						cfg_mismatches = true;
+
+					if (info->density != emc->basic_conf4.density)
+						cfg_mismatches = true;
+
+					if (info->io_width != emc->basic_conf4.io_width)
+						cfg_mismatches = true;
+
+					if (info->arch_type != emc->basic_conf4.arch_type)
+						cfg_mismatches = true;
+				} else {
+					dev_err(dev, "failed to parse %pOF\n", lpddr2_np);
+					cfg_mismatches = true;
+				}
+
+				of_node_put(lpddr2_np);
+			} else {
+				cfg_mismatches = true;
+			}
+
+			if (cfg_mismatches) {
+				of_node_put(np);
+				continue;
+			}
+		}
+
+		return np;
+	}
+
+	dev_err(dev, "no memory timings for RAM code %u found in device tree\n",
+		ram_code);
+
+	return NULL;
+}
+
+static int emc_read_lpddr_mode_register(struct tegra_emc *emc,
+					unsigned int emem_dev,
+					unsigned int register_addr,
+					unsigned int *register_data)
+{
+	u32 memory_dev = emem_dev ? 1 : 2;
+	u32 val, mr_mask = 0xff;
+	int err;
+
+	/* clear data-valid interrupt status */
+	writel_relaxed(EMC_MRR_DIVLD_INT, emc->regs + EMC_INTSTATUS);
+
+	/* issue mode register read request */
+	val  = FIELD_PREP(EMC_MRR_DEV_SELECTN, memory_dev);
+	val |= FIELD_PREP(EMC_MRR_MRR_MA, register_addr);
+
+	writel_relaxed(val, emc->regs + EMC_MRR);
+
+	/* wait for the LPDDR2 data-valid interrupt */
+	err = readl_relaxed_poll_timeout_atomic(emc->regs + EMC_INTSTATUS, val,
+						val & EMC_MRR_DIVLD_INT,
+						1, 100);
+	if (err) {
+		dev_err(emc->dev, "mode register %u read failed: %d\n",
+			register_addr, err);
+		emc->mrr_error = true;
+		return err;
+	}
+
+	/* read out mode register data */
+	val = readl_relaxed(emc->regs + EMC_MRR);
+	*register_data = FIELD_GET(EMC_MRR_MRR_DATA, val) & mr_mask;
+
+	return 0;
+}
+
+static void emc_read_lpddr_sdram_info(struct tegra_emc *emc,
+				      unsigned int emem_dev,
+				      bool print_out)
+{
+	/* these registers are standard for all LPDDR JEDEC memory chips */
+	emc_read_lpddr_mode_register(emc, emem_dev, 5, &emc->manufacturer_id);
+	emc_read_lpddr_mode_register(emc, emem_dev, 6, &emc->revision_id1);
+	emc_read_lpddr_mode_register(emc, emem_dev, 7, &emc->revision_id2);
+	emc_read_lpddr_mode_register(emc, emem_dev, 8, &emc->basic_conf4.value);
+
+	if (!print_out)
+		return;
+
+	dev_info(emc->dev, "SDRAM[dev%u]: manufacturer: 0x%x (%s) rev1: 0x%x rev2: 0x%x prefetch: S%u density: %uMbit iowidth: %ubit\n",
+		 emem_dev, emc->manufacturer_id,
+		 lpddr2_jedec_manufacturer(emc->manufacturer_id),
+		 emc->revision_id1, emc->revision_id2,
+		 4 >> emc->basic_conf4.arch_type,
+		 64 << emc->basic_conf4.density,
+		 32 >> emc->basic_conf4.io_width);
+}
+
+static int emc_setup_hw(struct tegra_emc *emc)
+{
+	u32 emc_cfg, emc_dbg, emc_fbio, emc_adr_cfg;
+	u32 intmask = EMC_REFRESH_OVERFLOW_INT;
+	static bool print_sdram_info_once;
+	enum emc_dram_type dram_type;
+	const char *dram_type_str;
+	unsigned int emem_numdev;
+
+	emc_cfg = readl_relaxed(emc->regs + EMC_CFG_2);
+
+	/*
+	 * Depending on a memory type, DRAM should enter either self-refresh
+	 * or power-down state on EMC clock change.
+	 */
+	if (!(emc_cfg & EMC_CLKCHANGE_PD_ENABLE) &&
+	    !(emc_cfg & EMC_CLKCHANGE_SR_ENABLE)) {
+		dev_err(emc->dev,
+			"bootloader didn't specify DRAM auto-suspend mode\n");
+		return -EINVAL;
+	}
+
+	/* enable EMC and CAR to handshake on PLL divider/source changes */
+	emc_cfg |= EMC_CLKCHANGE_REQ_ENABLE;
+	writel_relaxed(emc_cfg, emc->regs + EMC_CFG_2);
+
+	/* initialize interrupt */
+	writel_relaxed(intmask, emc->regs + EMC_INTMASK);
+	writel_relaxed(intmask, emc->regs + EMC_INTSTATUS);
+
+	/* ensure that unwanted debug features are disabled */
+	emc_dbg = readl_relaxed(emc->regs + EMC_DBG);
+	emc_dbg |= EMC_DBG_CFG_PRIORITY;
+	emc_dbg &= ~EMC_DBG_READ_MUX_ASSEMBLY;
+	emc_dbg &= ~EMC_DBG_WRITE_MUX_ACTIVE;
+	emc_dbg &= ~EMC_DBG_FORCE_UPDATE;
+	writel_relaxed(emc_dbg, emc->regs + EMC_DBG);
+
+	emc_fbio = readl_relaxed(emc->regs + EMC_FBIO_CFG5);
+
+	if (emc_fbio & EMC_FBIO_CFG5_DRAM_WIDTH_X16)
+		emc->dram_bus_width = 16;
+	else
+		emc->dram_bus_width = 32;
+
+	dram_type = FIELD_GET(EMC_FBIO_CFG5_DRAM_TYPE, emc_fbio);
+
+	switch (dram_type) {
+	case DRAM_TYPE_RESERVED:
+		dram_type_str = "INVALID";
+		break;
+	case DRAM_TYPE_DDR1:
+		dram_type_str = "DDR1";
+		break;
+	case DRAM_TYPE_LPDDR2:
+		dram_type_str = "LPDDR2";
+		break;
+	case DRAM_TYPE_DDR2:
+		dram_type_str = "DDR2";
+		break;
+	}
+
+	emc_adr_cfg = readl_relaxed(emc->regs + EMC_ADR_CFG_0);
+	emem_numdev = FIELD_GET(EMC_ADR_CFG_0_EMEM_NUMDEV, emc_adr_cfg) + 1;
+
+	dev_info_once(emc->dev, "%ubit DRAM bus, %u %s %s attached\n",
+		      emc->dram_bus_width, emem_numdev, dram_type_str,
+		      emem_numdev == 2 ? "devices" : "device");
+
+	if (dram_type == DRAM_TYPE_LPDDR2) {
+		while (emem_numdev--)
+			emc_read_lpddr_sdram_info(emc, emem_numdev,
+						  !print_sdram_info_once);
+		print_sdram_info_once = true;
+	}
+
+	return 0;
+}
+
+static long emc_round_rate(unsigned long rate,
+			   unsigned long min_rate,
+			   unsigned long max_rate,
+			   void *arg)
+{
+	struct emc_timing *timing = NULL;
+	struct tegra_emc *emc = arg;
+	unsigned int i;
+
+	if (!emc->num_timings)
+		return clk_get_rate(emc->clk);
+
+	min_rate = min(min_rate, emc->timings[emc->num_timings - 1].rate);
+
+	for (i = 0; i < emc->num_timings; i++) {
+		if (emc->timings[i].rate < rate && i != emc->num_timings - 1)
+			continue;
+
+		if (emc->timings[i].rate > max_rate) {
+			i = max(i, 1u) - 1;
+
+			if (emc->timings[i].rate < min_rate)
+				break;
+		}
+
+		if (emc->timings[i].rate < min_rate)
+			continue;
+
+		timing = &emc->timings[i];
+		break;
+	}
+
+	if (!timing) {
+		dev_err(emc->dev, "no timing for rate %lu min %lu max %lu\n",
+			rate, min_rate, max_rate);
+		return -EINVAL;
+	}
+
+	return timing->rate;
+}
+
+static void tegra_emc_rate_requests_init(struct tegra_emc *emc)
+{
+	unsigned int i;
+
+	for (i = 0; i < EMC_RATE_TYPE_MAX; i++) {
+		emc->requested_rate[i].min_rate = 0;
+		emc->requested_rate[i].max_rate = ULONG_MAX;
+	}
+}
+
+static int emc_request_rate(struct tegra_emc *emc,
+			    unsigned long new_min_rate,
+			    unsigned long new_max_rate,
+			    enum emc_rate_request_type type)
+{
+	struct emc_rate_request *req = emc->requested_rate;
+	unsigned long min_rate = 0, max_rate = ULONG_MAX;
+	unsigned int i;
+	int err;
+
+	/* select minimum and maximum rates among the requested rates */
+	for (i = 0; i < EMC_RATE_TYPE_MAX; i++, req++) {
+		if (i == type) {
+			min_rate = max(new_min_rate, min_rate);
+			max_rate = min(new_max_rate, max_rate);
+		} else {
+			min_rate = max(req->min_rate, min_rate);
+			max_rate = min(req->max_rate, max_rate);
+		}
+	}
+
+	if (min_rate > max_rate) {
+		dev_err_ratelimited(emc->dev, "%s: type %u: out of range: %lu %lu\n",
+				    __func__, type, min_rate, max_rate);
+		return -ERANGE;
+	}
+
+	/*
+	 * EMC rate-changes should go via OPP API because it manages voltage
+	 * changes.
+	 */
+	err = dev_pm_opp_set_rate(emc->dev, min_rate);
+	if (err)
+		return err;
+
+	emc->requested_rate[type].min_rate = new_min_rate;
+	emc->requested_rate[type].max_rate = new_max_rate;
+
+	return 0;
+}
+
+static int emc_set_min_rate(struct tegra_emc *emc, unsigned long rate,
+			    enum emc_rate_request_type type)
+{
+	struct emc_rate_request *req = &emc->requested_rate[type];
+	int ret;
+
+	mutex_lock(&emc->rate_lock);
+	ret = emc_request_rate(emc, rate, req->max_rate, type);
+	mutex_unlock(&emc->rate_lock);
+
+	return ret;
+}
+
+static int emc_set_max_rate(struct tegra_emc *emc, unsigned long rate,
+			    enum emc_rate_request_type type)
+{
+	struct emc_rate_request *req = &emc->requested_rate[type];
+	int ret;
+
+	mutex_lock(&emc->rate_lock);
+	ret = emc_request_rate(emc, req->min_rate, rate, type);
+	mutex_unlock(&emc->rate_lock);
+
+	return ret;
+}
+
+/*
+ * debugfs interface
+ *
+ * The memory controller driver exposes some files in debugfs that can be used
+ * to control the EMC frequency. The top-level directory can be found here:
+ *
+ *   /sys/kernel/debug/emc
+ *
+ * It contains the following files:
+ *
+ *   - available_rates: This file contains a list of valid, space-separated
+ *     EMC frequencies.
+ *
+ *   - min_rate: Writing a value to this file sets the given frequency as the
+ *       floor of the permitted range. If this is higher than the currently
+ *       configured EMC frequency, this will cause the frequency to be
+ *       increased so that it stays within the valid range.
+ *
+ *   - max_rate: Similarily to the min_rate file, writing a value to this file
+ *       sets the given frequency as the ceiling of the permitted range. If
+ *       the value is lower than the currently configured EMC frequency, this
+ *       will cause the frequency to be decreased so that it stays within the
+ *       valid range.
+ */
+
+static bool tegra_emc_validate_rate(struct tegra_emc *emc, unsigned long rate)
+{
+	unsigned int i;
+
+	for (i = 0; i < emc->num_timings; i++)
+		if (rate == emc->timings[i].rate)
+			return true;
+
+	return false;
+}
+
+static int tegra_emc_debug_available_rates_show(struct seq_file *s, void *data)
+{
+	struct tegra_emc *emc = s->private;
+	const char *prefix = "";
+	unsigned int i;
+
+	for (i = 0; i < emc->num_timings; i++) {
+		seq_printf(s, "%s%lu", prefix, emc->timings[i].rate);
+		prefix = " ";
+	}
+
+	seq_puts(s, "\n");
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(tegra_emc_debug_available_rates);
+
+static int tegra_emc_debug_min_rate_get(void *data, u64 *rate)
+{
+	struct tegra_emc *emc = data;
+
+	*rate = emc->debugfs.min_rate;
+
+	return 0;
+}
+
+static int tegra_emc_debug_min_rate_set(void *data, u64 rate)
+{
+	struct tegra_emc *emc = data;
+	int err;
+
+	if (!tegra_emc_validate_rate(emc, rate))
+		return -EINVAL;
+
+	err = emc_set_min_rate(emc, rate, EMC_RATE_DEBUG);
+	if (err < 0)
+		return err;
+
+	emc->debugfs.min_rate = rate;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(tegra_emc_debug_min_rate_fops,
+			tegra_emc_debug_min_rate_get,
+			tegra_emc_debug_min_rate_set, "%llu\n");
+
+static int tegra_emc_debug_max_rate_get(void *data, u64 *rate)
+{
+	struct tegra_emc *emc = data;
+
+	*rate = emc->debugfs.max_rate;
+
+	return 0;
+}
+
+static int tegra_emc_debug_max_rate_set(void *data, u64 rate)
+{
+	struct tegra_emc *emc = data;
+	int err;
+
+	if (!tegra_emc_validate_rate(emc, rate))
+		return -EINVAL;
+
+	err = emc_set_max_rate(emc, rate, EMC_RATE_DEBUG);
+	if (err < 0)
+		return err;
+
+	emc->debugfs.max_rate = rate;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(tegra_emc_debug_max_rate_fops,
+			tegra_emc_debug_max_rate_get,
+			tegra_emc_debug_max_rate_set, "%llu\n");
+
+static void tegra_emc_debugfs_init(struct tegra_emc *emc)
+{
+	struct device *dev = emc->dev;
+	unsigned int i;
+	int err;
+
+	emc->debugfs.min_rate = ULONG_MAX;
+	emc->debugfs.max_rate = 0;
+
+	for (i = 0; i < emc->num_timings; i++) {
+		if (emc->timings[i].rate < emc->debugfs.min_rate)
+			emc->debugfs.min_rate = emc->timings[i].rate;
+
+		if (emc->timings[i].rate > emc->debugfs.max_rate)
+			emc->debugfs.max_rate = emc->timings[i].rate;
+	}
+
+	if (!emc->num_timings) {
+		emc->debugfs.min_rate = clk_get_rate(emc->clk);
+		emc->debugfs.max_rate = emc->debugfs.min_rate;
+	}
+
+	err = clk_set_rate_range(emc->clk, emc->debugfs.min_rate,
+				 emc->debugfs.max_rate);
+	if (err < 0) {
+		dev_err(dev, "failed to set rate range [%lu-%lu] for %pC\n",
+			emc->debugfs.min_rate, emc->debugfs.max_rate,
+			emc->clk);
+	}
+
+	emc->debugfs.root = debugfs_create_dir("emc", NULL);
+
+	debugfs_create_file("available_rates", 0444, emc->debugfs.root,
+			    emc, &tegra_emc_debug_available_rates_fops);
+	debugfs_create_file("min_rate", 0644, emc->debugfs.root,
+			    emc, &tegra_emc_debug_min_rate_fops);
+	debugfs_create_file("max_rate", 0644, emc->debugfs.root,
+			    emc, &tegra_emc_debug_max_rate_fops);
+}
+
+static inline struct tegra_emc *
+to_tegra_emc_provider(struct icc_provider *provider)
+{
+	return container_of(provider, struct tegra_emc, provider);
+}
+
+static struct icc_node_data *
+emc_of_icc_xlate_extended(struct of_phandle_args *spec, void *data)
+{
+	struct icc_provider *provider = data;
+	struct icc_node_data *ndata;
+	struct icc_node *node;
+
+	/* External Memory is the only possible ICC route */
+	list_for_each_entry(node, &provider->nodes, node_list) {
+		if (node->id != TEGRA_ICC_EMEM)
+			continue;
+
+		ndata = kzalloc(sizeof(*ndata), GFP_KERNEL);
+		if (!ndata)
+			return ERR_PTR(-ENOMEM);
+
+		/*
+		 * SRC and DST nodes should have matching TAG in order to have
+		 * it set by default for a requested path.
+		 */
+		ndata->tag = TEGRA_MC_ICC_TAG_ISO;
+		ndata->node = node;
+
+		return ndata;
+	}
+
+	return ERR_PTR(-EPROBE_DEFER);
+}
+
+static int emc_icc_set(struct icc_node *src, struct icc_node *dst)
+{
+	struct tegra_emc *emc = to_tegra_emc_provider(dst->provider);
+	unsigned long long peak_bw = icc_units_to_bps(dst->peak_bw);
+	unsigned long long avg_bw = icc_units_to_bps(dst->avg_bw);
+	unsigned long long rate = max(avg_bw, peak_bw);
+	unsigned int dram_data_bus_width_bytes;
+	int err;
+
+	/*
+	 * Tegra20 EMC runs on x2 clock rate of SDRAM bus because DDR data
+	 * is sampled on both clock edges.  This means that EMC clock rate
+	 * equals to the peak data-rate.
+	 */
+	dram_data_bus_width_bytes = emc->dram_bus_width / 8;
+	do_div(rate, dram_data_bus_width_bytes);
+	rate = min_t(u64, rate, U32_MAX);
+
+	err = emc_set_min_rate(emc, rate, EMC_RATE_ICC);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static int tegra_emc_interconnect_init(struct tegra_emc *emc)
+{
+	const struct tegra_mc_soc *soc;
+	struct icc_node *node;
+	int err;
+
+	emc->mc = devm_tegra_memory_controller_get(emc->dev);
+	if (IS_ERR(emc->mc))
+		return PTR_ERR(emc->mc);
+
+	soc = emc->mc->soc;
+
+	emc->provider.dev = emc->dev;
+	emc->provider.set = emc_icc_set;
+	emc->provider.data = &emc->provider;
+	emc->provider.aggregate = soc->icc_ops->aggregate;
+	emc->provider.xlate_extended = emc_of_icc_xlate_extended;
+
+	icc_provider_init(&emc->provider);
+
+	/* create External Memory Controller node */
+	node = icc_node_create(TEGRA_ICC_EMC);
+	if (IS_ERR(node)) {
+		err = PTR_ERR(node);
+		goto err_msg;
+	}
+
+	node->name = "External Memory Controller";
+	icc_node_add(node, &emc->provider);
+
+	/* link External Memory Controller to External Memory (DRAM) */
+	err = icc_link_create(node, TEGRA_ICC_EMEM);
+	if (err)
+		goto remove_nodes;
+
+	/* create External Memory node */
+	node = icc_node_create(TEGRA_ICC_EMEM);
+	if (IS_ERR(node)) {
+		err = PTR_ERR(node);
+		goto remove_nodes;
+	}
+
+	node->name = "External Memory (DRAM)";
+	icc_node_add(node, &emc->provider);
+
+	err = icc_provider_register(&emc->provider);
+	if (err)
+		goto remove_nodes;
+
+	return 0;
+
+remove_nodes:
+	icc_nodes_remove(&emc->provider);
+err_msg:
+	dev_err(emc->dev, "failed to initialize ICC: %d\n", err);
+
+	return err;
+}
+
+static void devm_tegra_emc_unset_callback(void *data)
+{
+	tegra20_clk_set_emc_round_callback(NULL, NULL);
+}
+
+static void devm_tegra_emc_unreg_clk_notifier(void *data)
+{
+	struct tegra_emc *emc = data;
+
+	clk_notifier_unregister(emc->clk, &emc->clk_nb);
+}
+
+static int tegra_emc_init_clk(struct tegra_emc *emc)
+{
+	int err;
+
+	tegra20_clk_set_emc_round_callback(emc_round_rate, emc);
+
+	err = devm_add_action_or_reset(emc->dev, devm_tegra_emc_unset_callback,
+				       NULL);
+	if (err)
+		return err;
+
+	emc->clk = devm_clk_get(emc->dev, NULL);
+	if (IS_ERR(emc->clk)) {
+		dev_err(emc->dev, "failed to get EMC clock: %pe\n", emc->clk);
+		return PTR_ERR(emc->clk);
+	}
+
+	err = clk_notifier_register(emc->clk, &emc->clk_nb);
+	if (err) {
+		dev_err(emc->dev, "failed to register clk notifier: %d\n", err);
+		return err;
+	}
+
+	err = devm_add_action_or_reset(emc->dev,
+				       devm_tegra_emc_unreg_clk_notifier, emc);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static int tegra_emc_devfreq_target(struct device *dev, unsigned long *freq,
+				    u32 flags)
+{
+	struct tegra_emc *emc = dev_get_drvdata(dev);
+	struct dev_pm_opp *opp;
+	unsigned long rate;
+
+	opp = devfreq_recommended_opp(dev, freq, flags);
+	if (IS_ERR(opp)) {
+		dev_err(dev, "failed to find opp for %lu Hz\n", *freq);
+		return PTR_ERR(opp);
+	}
+
+	rate = dev_pm_opp_get_freq(opp);
+	dev_pm_opp_put(opp);
+
+	return emc_set_min_rate(emc, rate, EMC_RATE_DEVFREQ);
+}
+
+static int tegra_emc_devfreq_get_dev_status(struct device *dev,
+					    struct devfreq_dev_status *stat)
+{
+	struct tegra_emc *emc = dev_get_drvdata(dev);
+
+	/* freeze counters */
+	writel_relaxed(EMC_PWR_GATHER_DISABLE, emc->regs + EMC_STAT_CONTROL);
+
+	/*
+	 *  busy_time: number of clocks EMC request was accepted
+	 * total_time: number of clocks PWR_GATHER control was set to ENABLE
+	 */
+	stat->busy_time = readl_relaxed(emc->regs + EMC_STAT_PWR_COUNT);
+	stat->total_time = readl_relaxed(emc->regs + EMC_STAT_PWR_CLOCKS);
+	stat->current_frequency = clk_get_rate(emc->clk);
+
+	/* clear counters and restart */
+	writel_relaxed(EMC_PWR_GATHER_CLEAR, emc->regs + EMC_STAT_CONTROL);
+	writel_relaxed(EMC_PWR_GATHER_ENABLE, emc->regs + EMC_STAT_CONTROL);
+
+	return 0;
+}
+
+static struct devfreq_dev_profile tegra_emc_devfreq_profile = {
+	.polling_ms = 30,
+	.target = tegra_emc_devfreq_target,
+	.get_dev_status = tegra_emc_devfreq_get_dev_status,
+};
+
+static int tegra_emc_devfreq_init(struct tegra_emc *emc)
+{
+	struct devfreq *devfreq;
+
+	/*
+	 * PWR_COUNT is 1/2 of PWR_CLOCKS at max, and thus, the up-threshold
+	 * should be less than 50.  Secondly, multiple active memory clients
+	 * may cause over 20% of lost clock cycles due to stalls caused by
+	 * competing memory accesses.  This means that threshold should be
+	 * set to a less than 30 in order to have a properly working governor.
+	 */
+	emc->ondemand_data.upthreshold = 20;
+
+	/*
+	 * Reset statistic gathers state, select global bandwidth for the
+	 * statistics collection mode and set clocks counter saturation
+	 * limit to maximum.
+	 */
+	writel_relaxed(0x00000000, emc->regs + EMC_STAT_CONTROL);
+	writel_relaxed(0x00000000, emc->regs + EMC_STAT_LLMC_CONTROL);
+	writel_relaxed(0xffffffff, emc->regs + EMC_STAT_PWR_CLOCK_LIMIT);
+
+	devfreq = devm_devfreq_add_device(emc->dev, &tegra_emc_devfreq_profile,
+					  DEVFREQ_GOV_SIMPLE_ONDEMAND,
+					  &emc->ondemand_data);
+	if (IS_ERR(devfreq)) {
+		dev_err(emc->dev, "failed to initialize devfreq: %pe", devfreq);
+		return PTR_ERR(devfreq);
+	}
+
+	return 0;
+}
+
+static int tegra_emc_probe(struct platform_device *pdev)
+{
+	struct tegra_core_opp_params opp_params = {};
+	struct device_node *np;
+	struct tegra_emc *emc;
+	int irq, err;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "please update your device tree\n");
+		return irq;
+	}
+
+	emc = devm_kzalloc(&pdev->dev, sizeof(*emc), GFP_KERNEL);
+	if (!emc)
+		return -ENOMEM;
+
+	mutex_init(&emc->rate_lock);
+	emc->clk_nb.notifier_call = tegra_emc_clk_change_notify;
+	emc->dev = &pdev->dev;
+
+	emc->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(emc->regs))
+		return PTR_ERR(emc->regs);
+
+	err = emc_setup_hw(emc);
+	if (err)
+		return err;
+
+	np = tegra_emc_find_node_by_ram_code(emc);
+	if (np) {
+		err = tegra_emc_load_timings_from_dt(emc, np);
+		of_node_put(np);
+		if (err)
+			return err;
+	}
+
+	err = devm_request_irq(&pdev->dev, irq, tegra_emc_isr, 0,
+			       dev_name(&pdev->dev), emc);
+	if (err) {
+		dev_err(&pdev->dev, "failed to request IRQ: %d\n", err);
+		return err;
+	}
+
+	err = tegra_emc_init_clk(emc);
+	if (err)
+		return err;
+
+	opp_params.init_state = true;
+
+	err = devm_tegra_core_dev_init_opp_table(&pdev->dev, &opp_params);
+	if (err)
+		return err;
+
+	platform_set_drvdata(pdev, emc);
+	tegra_emc_rate_requests_init(emc);
+	tegra_emc_debugfs_init(emc);
+	tegra_emc_interconnect_init(emc);
+	tegra_emc_devfreq_init(emc);
+
+	/*
+	 * Don't allow the kernel module to be unloaded. Unloading adds some
+	 * extra complexity which doesn't really worth the effort in a case of
+	 * this driver.
+	 */
+	try_module_get(THIS_MODULE);
+
+	return 0;
+}
+
+static const struct of_device_id tegra_emc_of_match[] = {
+	{ .compatible = "nvidia,tegra20-emc", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, tegra_emc_of_match);
+
+static struct platform_driver tegra_emc_driver = {
+	.probe = tegra_emc_probe,
+	.driver = {
+		.name = "tegra20-emc",
+		.of_match_table = tegra_emc_of_match,
+		.suppress_bind_attrs = true,
+		.sync_state = icc_sync_state,
+	},
+};
+module_platform_driver(tegra_emc_driver);
+
+MODULE_AUTHOR("Dmitry Osipenko <digetx@gmail.com>");
+MODULE_DESCRIPTION("NVIDIA Tegra20 EMC driver");
+MODULE_SOFTDEP("pre: governor_simpleondemand");
+MODULE_LICENSE("GPL v2");