drivers/memory/jz4780-nemc.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * JZ4780 NAND/external memory controller (NEMC)
  *
  * Copyright (c) 2015 Imagination Technologies
  * Author: Alex Smith <alex@alex-smith.me.uk>
  */

 #include <linux/clk.h>
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/math64.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>

 #include <linux/jz4780-nemc.h>

 #define NEMC_SMCRn(n)		(0x14 + (((n) - 1) * 4))
 #define NEMC_NFCSR		0x50

 #define NEMC_REG_LEN		0x54

 #define NEMC_SMCR_SMT		BIT(0)
 #define NEMC_SMCR_BW_SHIFT	6
 #define NEMC_SMCR_BW_MASK	(0x3 << NEMC_SMCR_BW_SHIFT)
 #define NEMC_SMCR_BW_8		(0 << 6)
 #define NEMC_SMCR_TAS_SHIFT	8
 #define NEMC_SMCR_TAS_MASK	(0xf << NEMC_SMCR_TAS_SHIFT)
 #define NEMC_SMCR_TAH_SHIFT	12
 #define NEMC_SMCR_TAH_MASK	(0xf << NEMC_SMCR_TAH_SHIFT)
 #define NEMC_SMCR_TBP_SHIFT	16
 #define NEMC_SMCR_TBP_MASK	(0xf << NEMC_SMCR_TBP_SHIFT)
 #define NEMC_SMCR_TAW_SHIFT	20
 #define NEMC_SMCR_TAW_MASK	(0xf << NEMC_SMCR_TAW_SHIFT)
 #define NEMC_SMCR_TSTRV_SHIFT	24
 #define NEMC_SMCR_TSTRV_MASK	(0x3f << NEMC_SMCR_TSTRV_SHIFT)

 #define NEMC_NFCSR_NFEn(n)	BIT(((n) - 1) << 1)
 #define NEMC_NFCSR_NFCEn(n)	BIT((((n) - 1) << 1) + 1)
 #define NEMC_NFCSR_TNFEn(n)	BIT(16 + (n) - 1)

 struct jz_soc_info {
 	u8 tas_tah_cycles_max;
 };

 struct jz4780_nemc {
 	spinlock_t lock;
 	struct device *dev;
 	const struct jz_soc_info *soc_info;
 	void __iomem *base;
 	struct clk *clk;
 	uint32_t clk_period;
 	unsigned long banks_present;
 };

 /**
  * jz4780_nemc_num_banks() - count the number of banks referenced by a device
  * @dev: device to count banks for, must be a child of the NEMC.
  *
  * Return: The number of unique NEMC banks referred to by the specified NEMC
  * child device. Unique here means that a device that references the same bank
  * multiple times in its "reg" property will only count once.
  */
 unsigned int jz4780_nemc_num_banks(struct device *dev)
 {
 	const __be32 *prop;
 	unsigned int bank, count = 0;
 	unsigned long referenced = 0;
 	int i = 0;

 	while ((prop = of_get_address(dev->of_node, i++, NULL, NULL))) {
 		bank = of_read_number(prop, 1);
 		if (!(referenced & BIT(bank))) {
 			referenced |= BIT(bank);
 			count++;
 		}
 	}

 	return count;
 }
 EXPORT_SYMBOL(jz4780_nemc_num_banks);

 /**
  * jz4780_nemc_set_type() - set the type of device connected to a bank
  * @dev: child device of the NEMC.
  * @bank: bank number to configure.
  * @type: type of device connected to the bank.
  */
 void jz4780_nemc_set_type(struct device *dev, unsigned int bank,
 			  enum jz4780_nemc_bank_type type)
 {
 	struct jz4780_nemc *nemc = dev_get_drvdata(dev->parent);
 	uint32_t nfcsr;

 	nfcsr = readl(nemc->base + NEMC_NFCSR);

 	/* TODO: Support toggle NAND devices. */
 	switch (type) {
 	case JZ4780_NEMC_BANK_SRAM:
 		nfcsr &= ~(NEMC_NFCSR_TNFEn(bank) | NEMC_NFCSR_NFEn(bank));
 		break;
 	case JZ4780_NEMC_BANK_NAND:
 		nfcsr &= ~NEMC_NFCSR_TNFEn(bank);
 		nfcsr |= NEMC_NFCSR_NFEn(bank);
 		break;
 	}

 	writel(nfcsr, nemc->base + NEMC_NFCSR);
 }
 EXPORT_SYMBOL(jz4780_nemc_set_type);

 /**
  * jz4780_nemc_assert() - (de-)assert a NAND device's chip enable pin
  * @dev: child device of the NEMC.
  * @bank: bank number of device.
  * @assert: whether the chip enable pin should be asserted.
  *
  * (De-)asserts the chip enable pin for the NAND device connected to the
  * specified bank.
  */
 void jz4780_nemc_assert(struct device *dev, unsigned int bank, bool assert)
 {
 	struct jz4780_nemc *nemc = dev_get_drvdata(dev->parent);
 	uint32_t nfcsr;

 	nfcsr = readl(nemc->base + NEMC_NFCSR);

 	if (assert)
 		nfcsr |= NEMC_NFCSR_NFCEn(bank);
 	else
 		nfcsr &= ~NEMC_NFCSR_NFCEn(bank);

 	writel(nfcsr, nemc->base + NEMC_NFCSR);
 }
 EXPORT_SYMBOL(jz4780_nemc_assert);

 static uint32_t jz4780_nemc_clk_period(struct jz4780_nemc *nemc)
 {
 	unsigned long rate;

 	rate = clk_get_rate(nemc->clk);
 	if (!rate)
 		return 0;

 	/* Return in picoseconds. */
 	return div64_ul(1000000000000ull, rate);
 }

 static uint32_t jz4780_nemc_ns_to_cycles(struct jz4780_nemc *nemc, uint32_t ns)
 {
 	return ((ns * 1000) + nemc->clk_period - 1) / nemc->clk_period;
 }

 static bool jz4780_nemc_configure_bank(struct jz4780_nemc *nemc,
 				       unsigned int bank,
 				       struct device_node *node)
 {
 	uint32_t smcr, val, cycles;

 	/*
 	 * Conversion of tBP and tAW cycle counts to values supported by the
 	 * hardware (round up to the next supported value).
 	 */
 	static const u8 convert_tBP_tAW[] = {
 		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,

 		/* 11 - 12 -> 12 cycles */
 		11, 11,

 		/* 13 - 15 -> 15 cycles */
 		12, 12, 12,

 		/* 16 - 20 -> 20 cycles */
 		13, 13, 13, 13, 13,

 		/* 21 - 25 -> 25 cycles */
 		14, 14, 14, 14, 14,

 		/* 26 - 31 -> 31 cycles */
 		15, 15, 15, 15, 15, 15
 	};

 	smcr = readl(nemc->base + NEMC_SMCRn(bank));
 	smcr &= ~NEMC_SMCR_SMT;

 	if (!of_property_read_u32(node, "ingenic,nemc-bus-width", &val)) {
 		smcr &= ~NEMC_SMCR_BW_MASK;
 		switch (val) {
 		case 8:
 			smcr |= NEMC_SMCR_BW_8;
 			break;
 		default:
 			/*
 			 * Earlier SoCs support a 16 bit bus width (the 4780
 			 * does not), until those are properly supported, error.
 			 */
 			dev_err(nemc->dev, "unsupported bus width: %u\n", val);
 			return false;
 		}
 	}

 	if (of_property_read_u32(node, "ingenic,nemc-tAS", &val) == 0) {
 		smcr &= ~NEMC_SMCR_TAS_MASK;
 		cycles = jz4780_nemc_ns_to_cycles(nemc, val);
 		if (cycles > nemc->soc_info->tas_tah_cycles_max) {
 			dev_err(nemc->dev, "tAS %u is too high (%u cycles)\n",
 				val, cycles);
 			return false;
 		}

 		smcr |= cycles << NEMC_SMCR_TAS_SHIFT;
 	}

 	if (of_property_read_u32(node, "ingenic,nemc-tAH", &val) == 0) {
 		smcr &= ~NEMC_SMCR_TAH_MASK;
 		cycles = jz4780_nemc_ns_to_cycles(nemc, val);
 		if (cycles > nemc->soc_info->tas_tah_cycles_max) {
 			dev_err(nemc->dev, "tAH %u is too high (%u cycles)\n",
 				val, cycles);
 			return false;
 		}

 		smcr |= cycles << NEMC_SMCR_TAH_SHIFT;
 	}

 	if (of_property_read_u32(node, "ingenic,nemc-tBP", &val) == 0) {
 		smcr &= ~NEMC_SMCR_TBP_MASK;
 		cycles = jz4780_nemc_ns_to_cycles(nemc, val);
 		if (cycles > 31) {
 			dev_err(nemc->dev, "tBP %u is too high (%u cycles)\n",
 				val, cycles);
 			return false;
 		}

 		smcr |= convert_tBP_tAW[cycles] << NEMC_SMCR_TBP_SHIFT;
 	}

 	if (of_property_read_u32(node, "ingenic,nemc-tAW", &val) == 0) {
 		smcr &= ~NEMC_SMCR_TAW_MASK;
 		cycles = jz4780_nemc_ns_to_cycles(nemc, val);
 		if (cycles > 31) {
 			dev_err(nemc->dev, "tAW %u is too high (%u cycles)\n",
 				val, cycles);
 			return false;
 		}

 		smcr |= convert_tBP_tAW[cycles] << NEMC_SMCR_TAW_SHIFT;
 	}

 	if (of_property_read_u32(node, "ingenic,nemc-tSTRV", &val) == 0) {
 		smcr &= ~NEMC_SMCR_TSTRV_MASK;
 		cycles = jz4780_nemc_ns_to_cycles(nemc, val);
 		if (cycles > 63) {
 			dev_err(nemc->dev, "tSTRV %u is too high (%u cycles)\n",
 				val, cycles);
 			return false;
 		}

 		smcr |= cycles << NEMC_SMCR_TSTRV_SHIFT;
 	}

 	writel(smcr, nemc->base + NEMC_SMCRn(bank));
 	return true;
 }

 static int jz4780_nemc_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct jz4780_nemc *nemc;
 	struct resource *res;
 	struct device_node *child;
 	const __be32 *prop;
 	unsigned int bank;
 	unsigned long referenced;
 	int i, ret;

 	nemc = devm_kzalloc(dev, sizeof(*nemc), GFP_KERNEL);
 	if (!nemc)
 		return -ENOMEM;

 	nemc->soc_info = device_get_match_data(dev);
 	if (!nemc->soc_info)
 		return -EINVAL;

 	spin_lock_init(&nemc->lock);
 	nemc->dev = dev;

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!res)
 		return -EINVAL;

 	/*
 	 * The driver currently only uses the registers up to offset
 	 * NEMC_REG_LEN. Since the EFUSE registers are in the middle of the
 	 * NEMC registers, we only request the registers we will use for now;
 	 * that way the EFUSE driver can probe too.
 	 */
 	if (!devm_request_mem_region(dev, res->start, NEMC_REG_LEN, dev_name(dev))) {
 		dev_err(dev, "unable to request I/O memory region\n");
 		return -EBUSY;
 	}

 	nemc->base = devm_ioremap(dev, res->start, NEMC_REG_LEN);
 	if (!nemc->base) {
 		dev_err(dev, "failed to get I/O memory\n");
 		return -ENOMEM;
 	}

 	writel(0, nemc->base + NEMC_NFCSR);

 	nemc->clk = devm_clk_get(dev, NULL);
 	if (IS_ERR(nemc->clk)) {
 		dev_err(dev, "failed to get clock\n");
 		return PTR_ERR(nemc->clk);
 	}

 	ret = clk_prepare_enable(nemc->clk);
 	if (ret) {
 		dev_err(dev, "failed to enable clock: %d\n", ret);
 		return ret;
 	}

 	nemc->clk_period = jz4780_nemc_clk_period(nemc);
 	if (!nemc->clk_period) {
 		dev_err(dev, "failed to calculate clock period\n");
 		clk_disable_unprepare(nemc->clk);
 		return -EINVAL;
 	}

 	/*
 	 * Iterate over child devices, check that they do not conflict with
 	 * each other, and register child devices for them. If a child device
 	 * has invalid properties, it is ignored and no platform device is
 	 * registered for it.
 	 */
 	for_each_child_of_node(nemc->dev->of_node, child) {
 		referenced = 0;
 		i = 0;
 		while ((prop = of_get_address(child, i++, NULL, NULL))) {
 			bank = of_read_number(prop, 1);
 			if (bank < 1 || bank >= JZ4780_NEMC_NUM_BANKS) {
 				dev_err(nemc->dev,
 					"%pOF requests invalid bank %u\n",
 					child, bank);

 				/* Will continue the outer loop below. */
 				referenced = 0;
 				break;
 			}

 			referenced |= BIT(bank);
 		}

 		if (!referenced) {
 			dev_err(nemc->dev, "%pOF has no addresses\n",
 				child);
 			continue;
 		} else if (nemc->banks_present & referenced) {
 			dev_err(nemc->dev, "%pOF conflicts with another node\n",
 				child);
 			continue;
 		}

 		/* Configure bank parameters. */
 		for_each_set_bit(bank, &referenced, JZ4780_NEMC_NUM_BANKS) {
 			if (!jz4780_nemc_configure_bank(nemc, bank, child)) {
 				referenced = 0;
 				break;
 			}
 		}

 		if (referenced) {
 			if (of_platform_device_create(child, NULL, nemc->dev))
 				nemc->banks_present |= referenced;
 		}
 	}

 	platform_set_drvdata(pdev, nemc);
 	dev_info(dev, "JZ4780 NEMC initialised\n");
 	return 0;
 }

 static int jz4780_nemc_remove(struct platform_device *pdev)
 {
 	struct jz4780_nemc *nemc = platform_get_drvdata(pdev);

 	clk_disable_unprepare(nemc->clk);
 	return 0;
 }

 static const struct jz_soc_info jz4740_soc_info = {
 	.tas_tah_cycles_max = 7,
 };

 static const struct jz_soc_info jz4780_soc_info = {
 	.tas_tah_cycles_max = 15,
 };

 static const struct of_device_id jz4780_nemc_dt_match[] = {
 	{ .compatible = "ingenic,jz4740-nemc", .data = &jz4740_soc_info, },
 	{ .compatible = "ingenic,jz4780-nemc", .data = &jz4780_soc_info, },
 	{},
 };

 static struct platform_driver jz4780_nemc_driver = {
 	.probe		= jz4780_nemc_probe,
 	.remove		= jz4780_nemc_remove,
 	.driver	= {
 		.name	= "jz4780-nemc",
 		.of_match_table = of_match_ptr(jz4780_nemc_dt_match),
 	},
 };

 static int __init jz4780_nemc_init(void)
 {
 	return platform_driver_register(&jz4780_nemc_driver);
 }
 subsys_initcall(jz4780_nemc_init);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* JZ4780 NAND/external memory controller (NEMC)
	*
	* Copyright (c) 2015 Imagination Technologies
	* Author: Alex Smith <alex@alex-smith.me.uk>
	*/

	#include <linux/clk.h>
	#include <linux/init.h>
	#include <linux/io.h>
	#include <linux/math64.h>
	#include <linux/of.h>
	#include <linux/of_address.h>
	#include <linux/of_platform.h>
	#include <linux/platform_device.h>
	#include <linux/slab.h>
	#include <linux/spinlock.h>

	#include <linux/jz4780-nemc.h>

	#define NEMC_SMCRn(n) (0x14 + (((n) - 1) * 4))
	#define NEMC_NFCSR 0x50

	#define NEMC_REG_LEN 0x54

	#define NEMC_SMCR_SMT BIT(0)
	#define NEMC_SMCR_BW_SHIFT 6
	#define NEMC_SMCR_BW_MASK (0x3 << NEMC_SMCR_BW_SHIFT)
	#define NEMC_SMCR_BW_8 (0 << 6)
	#define NEMC_SMCR_TAS_SHIFT 8
	#define NEMC_SMCR_TAS_MASK (0xf << NEMC_SMCR_TAS_SHIFT)
	#define NEMC_SMCR_TAH_SHIFT 12
	#define NEMC_SMCR_TAH_MASK (0xf << NEMC_SMCR_TAH_SHIFT)
	#define NEMC_SMCR_TBP_SHIFT 16
	#define NEMC_SMCR_TBP_MASK (0xf << NEMC_SMCR_TBP_SHIFT)
	#define NEMC_SMCR_TAW_SHIFT 20
	#define NEMC_SMCR_TAW_MASK (0xf << NEMC_SMCR_TAW_SHIFT)
	#define NEMC_SMCR_TSTRV_SHIFT 24
	#define NEMC_SMCR_TSTRV_MASK (0x3f << NEMC_SMCR_TSTRV_SHIFT)

	#define NEMC_NFCSR_NFEn(n) BIT(((n) - 1) << 1)
	#define NEMC_NFCSR_NFCEn(n) BIT((((n) - 1) << 1) + 1)
	#define NEMC_NFCSR_TNFEn(n) BIT(16 + (n) - 1)

	struct jz_soc_info {
	u8 tas_tah_cycles_max;
	};

	struct jz4780_nemc {
	spinlock_t lock;
	struct device *dev;
	const struct jz_soc_info *soc_info;
	void __iomem *base;
	struct clk *clk;
	uint32_t clk_period;
	unsigned long banks_present;
	};

	/**
	* jz4780_nemc_num_banks() - count the number of banks referenced by a device
	* @dev: device to count banks for, must be a child of the NEMC.
	*
	* Return: The number of unique NEMC banks referred to by the specified NEMC
	* child device. Unique here means that a device that references the same bank
	* multiple times in its "reg" property will only count once.
	*/
	unsigned int jz4780_nemc_num_banks(struct device *dev)
	{
	const __be32 *prop;
	unsigned int bank, count = 0;
	unsigned long referenced = 0;
	int i = 0;

	while ((prop = of_get_address(dev->of_node, i++, NULL, NULL))) {
	bank = of_read_number(prop, 1);
	if (!(referenced & BIT(bank))) {
	referenced \|= BIT(bank);
	count++;
	}
	}

	return count;
	}
	EXPORT_SYMBOL(jz4780_nemc_num_banks);

	/**
	* jz4780_nemc_set_type() - set the type of device connected to a bank
	* @dev: child device of the NEMC.
	* @bank: bank number to configure.
	* @type: type of device connected to the bank.
	*/
	void jz4780_nemc_set_type(struct device *dev, unsigned int bank,
	enum jz4780_nemc_bank_type type)
	{
	struct jz4780_nemc *nemc = dev_get_drvdata(dev->parent);
	uint32_t nfcsr;

	nfcsr = readl(nemc->base + NEMC_NFCSR);

	/* TODO: Support toggle NAND devices. */
	switch (type) {
	case JZ4780_NEMC_BANK_SRAM:
	nfcsr &= ~(NEMC_NFCSR_TNFEn(bank) \| NEMC_NFCSR_NFEn(bank));
	break;
	case JZ4780_NEMC_BANK_NAND:
	nfcsr &= ~NEMC_NFCSR_TNFEn(bank);
	nfcsr \|= NEMC_NFCSR_NFEn(bank);
	break;
	}

	writel(nfcsr, nemc->base + NEMC_NFCSR);
	}
	EXPORT_SYMBOL(jz4780_nemc_set_type);

	/**
	* jz4780_nemc_assert() - (de-)assert a NAND device's chip enable pin
	* @dev: child device of the NEMC.
	* @bank: bank number of device.
	* @assert: whether the chip enable pin should be asserted.
	*
	* (De-)asserts the chip enable pin for the NAND device connected to the
	* specified bank.
	*/
	void jz4780_nemc_assert(struct device *dev, unsigned int bank, bool assert)
	{
	struct jz4780_nemc *nemc = dev_get_drvdata(dev->parent);
	uint32_t nfcsr;

	nfcsr = readl(nemc->base + NEMC_NFCSR);

	if (assert)
	nfcsr \|= NEMC_NFCSR_NFCEn(bank);
	else
	nfcsr &= ~NEMC_NFCSR_NFCEn(bank);

	writel(nfcsr, nemc->base + NEMC_NFCSR);
	}
	EXPORT_SYMBOL(jz4780_nemc_assert);

	static uint32_t jz4780_nemc_clk_period(struct jz4780_nemc *nemc)
	{
	unsigned long rate;

	rate = clk_get_rate(nemc->clk);
	if (!rate)
	return 0;

	/* Return in picoseconds. */
	return div64_ul(1000000000000ull, rate);
	}

	static uint32_t jz4780_nemc_ns_to_cycles(struct jz4780_nemc *nemc, uint32_t ns)
	{
	return ((ns * 1000) + nemc->clk_period - 1) / nemc->clk_period;
	}

	static bool jz4780_nemc_configure_bank(struct jz4780_nemc *nemc,
	unsigned int bank,
	struct device_node *node)
	{
	uint32_t smcr, val, cycles;

	/*
	* Conversion of tBP and tAW cycle counts to values supported by the
	* hardware (round up to the next supported value).
	*/
	static const u8 convert_tBP_tAW[] = {
	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,

	/* 11 - 12 -> 12 cycles */
	11, 11,

	/* 13 - 15 -> 15 cycles */
	12, 12, 12,

	/* 16 - 20 -> 20 cycles */
	13, 13, 13, 13, 13,

	/* 21 - 25 -> 25 cycles */
	14, 14, 14, 14, 14,

	/* 26 - 31 -> 31 cycles */
	15, 15, 15, 15, 15, 15
	};

	smcr = readl(nemc->base + NEMC_SMCRn(bank));
	smcr &= ~NEMC_SMCR_SMT;

	if (!of_property_read_u32(node, "ingenic,nemc-bus-width", &val)) {
	smcr &= ~NEMC_SMCR_BW_MASK;
	switch (val) {
	case 8:
	smcr \|= NEMC_SMCR_BW_8;
	break;
	default:
	/*
	* Earlier SoCs support a 16 bit bus width (the 4780
	* does not), until those are properly supported, error.
	*/
	dev_err(nemc->dev, "unsupported bus width: %u\n", val);
	return false;
	}
	}

	if (of_property_read_u32(node, "ingenic,nemc-tAS", &val) == 0) {
	smcr &= ~NEMC_SMCR_TAS_MASK;
	cycles = jz4780_nemc_ns_to_cycles(nemc, val);
	if (cycles > nemc->soc_info->tas_tah_cycles_max) {
	dev_err(nemc->dev, "tAS %u is too high (%u cycles)\n",
	val, cycles);
	return false;
	}

	smcr \|= cycles << NEMC_SMCR_TAS_SHIFT;
	}

	if (of_property_read_u32(node, "ingenic,nemc-tAH", &val) == 0) {
	smcr &= ~NEMC_SMCR_TAH_MASK;
	cycles = jz4780_nemc_ns_to_cycles(nemc, val);
	if (cycles > nemc->soc_info->tas_tah_cycles_max) {
	dev_err(nemc->dev, "tAH %u is too high (%u cycles)\n",
	val, cycles);
	return false;
	}

	smcr \|= cycles << NEMC_SMCR_TAH_SHIFT;
	}

	if (of_property_read_u32(node, "ingenic,nemc-tBP", &val) == 0) {
	smcr &= ~NEMC_SMCR_TBP_MASK;
	cycles = jz4780_nemc_ns_to_cycles(nemc, val);
	if (cycles > 31) {
	dev_err(nemc->dev, "tBP %u is too high (%u cycles)\n",
	val, cycles);
	return false;
	}

	smcr \|= convert_tBP_tAW[cycles] << NEMC_SMCR_TBP_SHIFT;
	}

	if (of_property_read_u32(node, "ingenic,nemc-tAW", &val) == 0) {
	smcr &= ~NEMC_SMCR_TAW_MASK;
	cycles = jz4780_nemc_ns_to_cycles(nemc, val);
	if (cycles > 31) {
	dev_err(nemc->dev, "tAW %u is too high (%u cycles)\n",
	val, cycles);
	return false;
	}

	smcr \|= convert_tBP_tAW[cycles] << NEMC_SMCR_TAW_SHIFT;
	}

	if (of_property_read_u32(node, "ingenic,nemc-tSTRV", &val) == 0) {
	smcr &= ~NEMC_SMCR_TSTRV_MASK;
	cycles = jz4780_nemc_ns_to_cycles(nemc, val);
	if (cycles > 63) {
	dev_err(nemc->dev, "tSTRV %u is too high (%u cycles)\n",
	val, cycles);
	return false;
	}

	smcr \|= cycles << NEMC_SMCR_TSTRV_SHIFT;
	}

	writel(smcr, nemc->base + NEMC_SMCRn(bank));
	return true;
	}

	static int jz4780_nemc_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	struct jz4780_nemc *nemc;
	struct resource *res;
	struct device_node *child;
	const __be32 *prop;
	unsigned int bank;
	unsigned long referenced;
	int i, ret;

	nemc = devm_kzalloc(dev, sizeof(*nemc), GFP_KERNEL);
	if (!nemc)
	return -ENOMEM;

	nemc->soc_info = device_get_match_data(dev);
	if (!nemc->soc_info)
	return -EINVAL;

	spin_lock_init(&nemc->lock);
	nemc->dev = dev;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
	return -EINVAL;

	/*
	* The driver currently only uses the registers up to offset
	* NEMC_REG_LEN. Since the EFUSE registers are in the middle of the
	* NEMC registers, we only request the registers we will use for now;
	* that way the EFUSE driver can probe too.
	*/
	if (!devm_request_mem_region(dev, res->start, NEMC_REG_LEN, dev_name(dev))) {
	dev_err(dev, "unable to request I/O memory region\n");
	return -EBUSY;
	}

	nemc->base = devm_ioremap(dev, res->start, NEMC_REG_LEN);
	if (!nemc->base) {
	dev_err(dev, "failed to get I/O memory\n");
	return -ENOMEM;
	}

	writel(0, nemc->base + NEMC_NFCSR);

	nemc->clk = devm_clk_get(dev, NULL);
	if (IS_ERR(nemc->clk)) {
	dev_err(dev, "failed to get clock\n");
	return PTR_ERR(nemc->clk);
	}

	ret = clk_prepare_enable(nemc->clk);
	if (ret) {
	dev_err(dev, "failed to enable clock: %d\n", ret);
	return ret;
	}

	nemc->clk_period = jz4780_nemc_clk_period(nemc);
	if (!nemc->clk_period) {
	dev_err(dev, "failed to calculate clock period\n");
	clk_disable_unprepare(nemc->clk);
	return -EINVAL;
	}

	/*
	* Iterate over child devices, check that they do not conflict with
	* each other, and register child devices for them. If a child device
	* has invalid properties, it is ignored and no platform device is
	* registered for it.
	*/
	for_each_child_of_node(nemc->dev->of_node, child) {
	referenced = 0;
	i = 0;
	while ((prop = of_get_address(child, i++, NULL, NULL))) {
	bank = of_read_number(prop, 1);
	if (bank < 1 \|\| bank >= JZ4780_NEMC_NUM_BANKS) {
	dev_err(nemc->dev,
	"%pOF requests invalid bank %u\n",
	child, bank);

	/* Will continue the outer loop below. */
	referenced = 0;
	break;
	}

	referenced \|= BIT(bank);
	}

	if (!referenced) {
	dev_err(nemc->dev, "%pOF has no addresses\n",
	child);
	continue;
	} else if (nemc->banks_present & referenced) {
	dev_err(nemc->dev, "%pOF conflicts with another node\n",
	child);
	continue;
	}

	/* Configure bank parameters. */
	for_each_set_bit(bank, &referenced, JZ4780_NEMC_NUM_BANKS) {
	if (!jz4780_nemc_configure_bank(nemc, bank, child)) {
	referenced = 0;
	break;
	}
	}

	if (referenced) {
	if (of_platform_device_create(child, NULL, nemc->dev))
	nemc->banks_present \|= referenced;
	}
	}

	platform_set_drvdata(pdev, nemc);
	dev_info(dev, "JZ4780 NEMC initialised\n");
	return 0;
	}

	static int jz4780_nemc_remove(struct platform_device *pdev)
	{
	struct jz4780_nemc *nemc = platform_get_drvdata(pdev);

	clk_disable_unprepare(nemc->clk);
	return 0;
	}

	static const struct jz_soc_info jz4740_soc_info = {
	.tas_tah_cycles_max = 7,
	};

	static const struct jz_soc_info jz4780_soc_info = {
	.tas_tah_cycles_max = 15,
	};

	static const struct of_device_id jz4780_nemc_dt_match[] = {
	{ .compatible = "ingenic,jz4740-nemc", .data = &jz4740_soc_info, },
	{ .compatible = "ingenic,jz4780-nemc", .data = &jz4780_soc_info, },
	{},
	};

	static struct platform_driver jz4780_nemc_driver = {
	.probe = jz4780_nemc_probe,
	.remove = jz4780_nemc_remove,
	.driver = {
	.name = "jz4780-nemc",
	.of_match_table = of_match_ptr(jz4780_nemc_dt_match),
	},
	};

	static int __init jz4780_nemc_init(void)
	{
	return platform_driver_register(&jz4780_nemc_driver);
	}
	subsys_initcall(jz4780_nemc_init);