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/of_device.h>
18#include <linux/platform_device.h>
19#include <linux/string.h>
20#include <linux/types.h>
21
22#include "physmap-bt1-rom.h"
23
24/*
25 * Baikal-T1 SoC ROMs are only accessible by the dword-aligned instructions.
26 * We have to take this into account when implementing the data read-methods.
27 * Note there is no need in bothering with endianness, since both Baikal-T1
28 * CPU and MMIO are LE.
29 */
30static map_word __xipram bt1_rom_map_read(struct map_info *map,
31					  unsigned long ofs)
32{
33	void __iomem *src = map->virt + ofs;
34	unsigned long shift;
35	map_word ret;
36	u32 data;
37
38	/* Read data within offset dword. */
39	shift = (unsigned long)src & 0x3;
40	data = readl_relaxed(src - shift);
41	if (!shift) {
42		ret.x[0] = data;
43		return ret;
44	}
45	ret.x[0] = data >> (shift * BITS_PER_BYTE);
46
47	/* Read data from the next dword. */
48	shift = 4 - shift;
49	if (ofs + shift >= map->size)
50		return ret;
51
52	data = readl_relaxed(src + shift);
53	ret.x[0] |= data << (shift * BITS_PER_BYTE);
54
55	return ret;
56}
57
58static void __xipram bt1_rom_map_copy_from(struct map_info *map,
59					   void *to, unsigned long from,
60					   ssize_t len)
61{
62	void __iomem *src = map->virt + from;
63	ssize_t shift, chunk;
64	u32 data;
65
66	if (len <= 0 || from >= map->size)
67		return;
68
69	/* Make sure we don't go over the map limit. */
70	len = min_t(ssize_t, map->size - from, len);
71
72	/*
73	 * Since requested data size can be pretty big we have to implement
74	 * the copy procedure as optimal as possible. That's why it's split
75	 * up into the next three stages: unaligned head, aligned body,
76	 * unaligned tail.
77	 */
78	shift = (ssize_t)src & 0x3;
79	if (shift) {
80		chunk = min_t(ssize_t, 4 - shift, len);
81		data = readl_relaxed(src - shift);
82		memcpy(to, (char *)&data + shift, chunk);
83		src += chunk;
84		to += chunk;
85		len -= chunk;
86	}
87
88	while (len >= 4) {
89		data = readl_relaxed(src);
90		memcpy(to, &data, 4);
91		src += 4;
92		to += 4;
93		len -= 4;
94	}
95
96	if (len) {
97		data = readl_relaxed(src);
98		memcpy(to, &data, len);
99	}
100}
101
102int of_flash_probe_bt1_rom(struct platform_device *pdev,
103			   struct device_node *np,
104			   struct map_info *map)
105{
106	struct device *dev = &pdev->dev;
107
108	/* It's supposed to be read-only MTD. */
109	if (!of_device_is_compatible(np, "mtd-rom")) {
110		dev_info(dev, "No mtd-rom compatible string\n");
111		return 0;
112	}
113
114	/* Multiplatform guard. */
115	if (!of_device_is_compatible(np, "baikal,bt1-int-rom"))
116		return 0;
117
118	/* Sanity check the device parameters retrieved from DTB. */
119	if (map->bankwidth != 4)
120		dev_warn(dev, "Bank width is supposed to be 32 bits wide\n");
121
122	map->read = bt1_rom_map_read;
123	map->copy_from = bt1_rom_map_copy_from;
124
125	return 0;
126}
127