// SPDX-License-Identifier: GPL-2.0
/*
 * JZ4740 ECC controller driver
 *
 * Copyright (c) 2019 Paul Cercueil <paul@crapouillou.net>
 *
 * based on jz4740-nand.c
 */

#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>

#include "ingenic_ecc.h"

#define JZ_REG_NAND_ECC_CTRL	0x00
#define JZ_REG_NAND_DATA	0x04
#define JZ_REG_NAND_PAR0	0x08
#define JZ_REG_NAND_PAR1	0x0C
#define JZ_REG_NAND_PAR2	0x10
#define JZ_REG_NAND_IRQ_STAT	0x14
#define JZ_REG_NAND_IRQ_CTRL	0x18
#define JZ_REG_NAND_ERR(x)	(0x1C + ((x) << 2))

#define JZ_NAND_ECC_CTRL_PAR_READY	BIT(4)
#define JZ_NAND_ECC_CTRL_ENCODING	BIT(3)
#define JZ_NAND_ECC_CTRL_RS		BIT(2)
#define JZ_NAND_ECC_CTRL_RESET		BIT(1)
#define JZ_NAND_ECC_CTRL_ENABLE		BIT(0)

#define JZ_NAND_STATUS_ERR_COUNT	(BIT(31) | BIT(30) | BIT(29))
#define JZ_NAND_STATUS_PAD_FINISH	BIT(4)
#define JZ_NAND_STATUS_DEC_FINISH	BIT(3)
#define JZ_NAND_STATUS_ENC_FINISH	BIT(2)
#define JZ_NAND_STATUS_UNCOR_ERROR	BIT(1)
#define JZ_NAND_STATUS_ERROR		BIT(0)

static const uint8_t empty_block_ecc[] = {
	0xcd, 0x9d, 0x90, 0x58, 0xf4, 0x8b, 0xff, 0xb7, 0x6f
};

static void jz4740_ecc_reset(struct ingenic_ecc *ecc, bool calc_ecc)
{
	uint32_t reg;

	/* Clear interrupt status */
	writel(0, ecc->base + JZ_REG_NAND_IRQ_STAT);

	/* Initialize and enable ECC hardware */
	reg = readl(ecc->base + JZ_REG_NAND_ECC_CTRL);
	reg |= JZ_NAND_ECC_CTRL_RESET;
	reg |= JZ_NAND_ECC_CTRL_ENABLE;
	reg |= JZ_NAND_ECC_CTRL_RS;
	if (calc_ecc) /* calculate ECC from data */
		reg |= JZ_NAND_ECC_CTRL_ENCODING;
	else /* correct data from ECC */
		reg &= ~JZ_NAND_ECC_CTRL_ENCODING;

	writel(reg, ecc->base + JZ_REG_NAND_ECC_CTRL);
}

static int jz4740_ecc_calculate(struct ingenic_ecc *ecc,
				struct ingenic_ecc_params *params,
				const u8 *buf, u8 *ecc_code)
{
	uint32_t reg, status;
	unsigned int timeout = 1000;
	int i;

	jz4740_ecc_reset(ecc, true);

	do {
		status = readl(ecc->base + JZ_REG_NAND_IRQ_STAT);
	} while (!(status & JZ_NAND_STATUS_ENC_FINISH) && --timeout);

	if (timeout == 0)
		return -ETIMEDOUT;

	reg = readl(ecc->base + JZ_REG_NAND_ECC_CTRL);
	reg &= ~JZ_NAND_ECC_CTRL_ENABLE;
	writel(reg, ecc->base + JZ_REG_NAND_ECC_CTRL);

	for (i = 0; i < params->bytes; ++i)
		ecc_code[i] = readb(ecc->base + JZ_REG_NAND_PAR0 + i);

	/*
	 * If the written data is completely 0xff, we also want to write 0xff as
	 * ECC, otherwise we will get in trouble when doing subpage writes.
	 */
	if (memcmp(ecc_code, empty_block_ecc, sizeof(empty_block_ecc)) == 0)
		memset(ecc_code, 0xff, sizeof(empty_block_ecc));

	return 0;
}

static void jz_nand_correct_data(uint8_t *buf, int index, int mask)
{
	int offset = index & 0x7;
	uint16_t data;

	index += (index >> 3);

	data = buf[index];
	data |= buf[index + 1] << 8;

	mask ^= (data >> offset) & 0x1ff;
	data &= ~(0x1ff << offset);
	data |= (mask << offset);

	buf[index] = data & 0xff;
	buf[index + 1] = (data >> 8) & 0xff;
}

static int jz4740_ecc_correct(struct ingenic_ecc *ecc,
			      struct ingenic_ecc_params *params,
			      u8 *buf, u8 *ecc_code)
{
	int i, error_count, index;
	uint32_t reg, status, error;
	unsigned int timeout = 1000;

	jz4740_ecc_reset(ecc, false);

	for (i = 0; i < params->bytes; ++i)
		writeb(ecc_code[i], ecc->base + JZ_REG_NAND_PAR0 + i);

	reg = readl(ecc->base + JZ_REG_NAND_ECC_CTRL);
	reg |= JZ_NAND_ECC_CTRL_PAR_READY;
	writel(reg, ecc->base + JZ_REG_NAND_ECC_CTRL);

	do {
		status = readl(ecc->base + JZ_REG_NAND_IRQ_STAT);
	} while (!(status & JZ_NAND_STATUS_DEC_FINISH) && --timeout);

	if (timeout == 0)
		return -ETIMEDOUT;

	reg = readl(ecc->base + JZ_REG_NAND_ECC_CTRL);
	reg &= ~JZ_NAND_ECC_CTRL_ENABLE;
	writel(reg, ecc->base + JZ_REG_NAND_ECC_CTRL);

	if (status & JZ_NAND_STATUS_ERROR) {
		if (status & JZ_NAND_STATUS_UNCOR_ERROR)
			return -EBADMSG;

		error_count = (status & JZ_NAND_STATUS_ERR_COUNT) >> 29;

		for (i = 0; i < error_count; ++i) {
			error = readl(ecc->base + JZ_REG_NAND_ERR(i));
			index = ((error >> 16) & 0x1ff) - 1;
			if (index >= 0 && index < params->size)
				jz_nand_correct_data(buf, index, error & 0x1ff);
		}

		return error_count;
	}

	return 0;
}

static void jz4740_ecc_disable(struct ingenic_ecc *ecc)
{
	u32 reg;

	writel(0, ecc->base + JZ_REG_NAND_IRQ_STAT);
	reg = readl(ecc->base + JZ_REG_NAND_ECC_CTRL);
	reg &= ~JZ_NAND_ECC_CTRL_ENABLE;
	writel(reg, ecc->base + JZ_REG_NAND_ECC_CTRL);
}

static const struct ingenic_ecc_ops jz4740_ecc_ops = {
	.disable = jz4740_ecc_disable,
	.calculate = jz4740_ecc_calculate,
	.correct = jz4740_ecc_correct,
};

static const struct of_device_id jz4740_ecc_dt_match[] = {
	{ .compatible = "ingenic,jz4740-ecc", .data = &jz4740_ecc_ops },
	{},
};
MODULE_DEVICE_TABLE(of, jz4740_ecc_dt_match);

static struct platform_driver jz4740_ecc_driver = {
	.probe		= ingenic_ecc_probe,
	.driver	= {
		.name	= "jz4740-ecc",
		.of_match_table = jz4740_ecc_dt_match,
	},
};
module_platform_driver(jz4740_ecc_driver);

MODULE_AUTHOR("Paul Cercueil <paul@crapouillou.net>");
MODULE_DESCRIPTION("Ingenic JZ4740 ECC controller driver");
MODULE_LICENSE("GPL v2");