xref: /kernel/linux/linux-6.6/drivers/mtd/maps/physmap-ixp4xx.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Intel IXP4xx OF physmap add-on
 * Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
 *
 * Based on the ixp4xx.c map driver, originally written by:
 * Intel Corporation
 * Deepak Saxena <dsaxena@mvista.com>
 * Copyright (C) 2002 Intel Corporation
 * Copyright (C) 2003-2004 MontaVista Software, Inc.
 */
#include <linux/export.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/mtd/map.h>
#include <linux/mtd/xip.h>
#include "physmap-ixp4xx.h"

/*
 * Read/write a 16 bit word from flash address 'addr'.
 *
 * When the cpu is in little-endian mode it swizzles the address lines
 * ('address coherency') so we need to undo the swizzling to ensure commands
 * and the like end up on the correct flash address.
 *
 * To further complicate matters, due to the way the expansion bus controller
 * handles 32 bit reads, the byte stream ABCD is stored on the flash as:
 *     D15    D0
 *     +---+---+
 *     | A | B | 0
 *     +---+---+
 *     | C | D | 2
 *     +---+---+
 * This means that on LE systems each 16 bit word must be swapped. Note that
 * this requires CONFIG_MTD_CFI_BE_BYTE_SWAP to be enabled to 'unswap' the CFI
 * data and other flash commands which are always in D7-D0.
 */
#ifndef CONFIG_CPU_BIG_ENDIAN

static inline u16 flash_read16(void __iomem *addr)
{
	return be16_to_cpu(__raw_readw((void __iomem *)((unsigned long)addr ^ 0x2)));
}

static inline void flash_write16(u16 d, void __iomem *addr)
{
	__raw_writew(cpu_to_be16(d), (void __iomem *)((unsigned long)addr ^ 0x2));
}

#define	BYTE0(h)	((h) & 0xFF)
#define	BYTE1(h)	(((h) >> 8) & 0xFF)

#else

static inline u16 flash_read16(const void __iomem *addr)
{
	return __raw_readw(addr);
}

static inline void flash_write16(u16 d, void __iomem *addr)
{
	__raw_writew(d, addr);
}

#define	BYTE0(h)	(((h) >> 8) & 0xFF)
#define	BYTE1(h)	((h) & 0xFF)
#endif

static map_word ixp4xx_read16(struct map_info *map, unsigned long ofs)
{
	map_word val;

	val.x[0] = flash_read16(map->virt + ofs);
	return val;
}

/*
 * The IXP4xx expansion bus only allows 16-bit wide acceses
 * when attached to a 16-bit wide device (such as the 28F128J3A),
 * so we can't just memcpy_fromio().
 */
static void ixp4xx_copy_from(struct map_info *map, void *to,
			     unsigned long from, ssize_t len)
{
	u8 *dest = (u8 *) to;
	void __iomem *src = map->virt + from;

	if (len <= 0)
		return;

	if (from & 1) {
		*dest++ = BYTE1(flash_read16(src-1));
		src++;
		--len;
	}

	while (len >= 2) {
		u16 data = flash_read16(src);
		*dest++ = BYTE0(data);
		*dest++ = BYTE1(data);
		src += 2;
		len -= 2;
	}

	if (len > 0)
		*dest++ = BYTE0(flash_read16(src));
}

static void ixp4xx_write16(struct map_info *map, map_word d, unsigned long adr)
{
	flash_write16(d.x[0], map->virt + adr);
}

int of_flash_probe_ixp4xx(struct platform_device *pdev,
			  struct device_node *np,
			  struct map_info *map)
{
	struct device *dev = &pdev->dev;

	/* Multiplatform guard */
	if (!of_device_is_compatible(np, "intel,ixp4xx-flash"))
		return 0;

	map->read = ixp4xx_read16;
	map->write = ixp4xx_write16;
	map->copy_from = ixp4xx_copy_from;
	map->copy_to = NULL;

	dev_info(dev, "initialized Intel IXP4xx-specific physmap control\n");

	return 0;
}