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(device: 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(device: 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

source code of linux/drivers/mtd/maps/physmap-bt1-rom.c