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}
126