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  */
29 static 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 
57 static 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 
101 int 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