physmap-bt1-rom.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
  4 *
  5 * Authors:
  6 *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
  7 *
  8 * Baikal-T1 Physically Mapped Internal ROM driver
  9 */
 10#include <linux/bits.h>
 11#include <linux/device.h>
 12#include <linux/kernel.h>
 13#include <linux/mtd/map.h>
 14#include <linux/mtd/xip.h>
 15#include <linux/mux/consumer.h>
 16#include <linux/of.h>
 17#include <linux/platform_device.h>
 18#include <linux/string.h>
 19#include <linux/types.h>
 20
 21#include "physmap-bt1-rom.h"
 22
 23/*
 24 * Baikal-T1 SoC ROMs are only accessible by the dword-aligned instructions.
 25 * We have to take this into account when implementing the data read-methods.
 26 * Note there is no need in bothering with endianness, since both Baikal-T1
 27 * CPU and MMIO are LE.
 28 */
 29static map_word __xipram bt1_rom_map_read(struct map_info *map,
 30					  unsigned long ofs)
 31{
 32	void __iomem *src = map->virt + ofs;
 33	unsigned int shift;
 34	map_word ret;
 35	u32 data;
 36
 37	/* Read data within offset dword. */
 38	shift = (uintptr_t)src & 0x3;
 39	data = readl_relaxed(src - shift);
 40	if (!shift) {
 41		ret.x[0] = data;
 42		return ret;
 43	}
 44	ret.x[0] = data >> (shift * BITS_PER_BYTE);
 45
 46	/* Read data from the next dword. */
 47	shift = 4 - shift;
 48	if (ofs + shift >= map->size)
 49		return ret;
 50
 51	data = readl_relaxed(src + shift);
 52	ret.x[0] |= data << (shift * BITS_PER_BYTE);
 53
 54	return ret;
 55}
 56
 57static void __xipram bt1_rom_map_copy_from(struct map_info *map,
 58					   void *to, unsigned long from,
 59					   ssize_t len)
 60{
 61	void __iomem *src = map->virt + from;
 62	unsigned int shift, chunk;
 63	u32 data;
 64
 65	if (len <= 0 || from >= map->size)
 66		return;
 67
 68	/* Make sure we don't go over the map limit. */
 69	len = min_t(ssize_t, map->size - from, len);
 70
 71	/*
 72	 * Since requested data size can be pretty big we have to implement
 73	 * the copy procedure as optimal as possible. That's why it's split
 74	 * up into the next three stages: unaligned head, aligned body,
 75	 * unaligned tail.
 76	 */
 77	shift = (uintptr_t)src & 0x3;
 78	if (shift) {
 79		chunk = min_t(ssize_t, 4 - shift, len);
 80		data = readl_relaxed(src - shift);
 81		memcpy(to, (char *)&data + shift, chunk);
 82		src += chunk;
 83		to += chunk;
 84		len -= chunk;
 85	}
 86
 87	while (len >= 4) {
 88		data = readl_relaxed(src);
 89		memcpy(to, &data, 4);
 90		src += 4;
 91		to += 4;
 92		len -= 4;
 93	}
 94
 95	if (len) {
 96		data = readl_relaxed(src);
 97		memcpy(to, &data, len);
 98	}
 99}
100
101int of_flash_probe_bt1_rom(struct platform_device *pdev,
102			   struct device_node *np,
103			   struct map_info *map)
104{
105	struct device *dev = &pdev->dev;
106
107	/* It's supposed to be read-only MTD. */
108	if (!of_device_is_compatible(np, "mtd-rom")) {
109		dev_info(dev, "No mtd-rom compatible string\n");
110		return 0;
111	}
112
113	/* Multiplatform guard. */
114	if (!of_device_is_compatible(np, "baikal,bt1-int-rom"))
115		return 0;
116
117	/* Sanity check the device parameters retrieved from DTB. */
118	if (map->bankwidth != 4)
119		dev_warn(dev, "Bank width is supposed to be 32 bits wide\n");
120
121	map->read = bt1_rom_map_read;
122	map->copy_from = bt1_rom_map_copy_from;
123
124	return 0;
125}