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  */
30 static 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 int shift;
35 	map_word ret;
36 	u32 data;
37 
38 	/* Read data within offset dword. */
39 	shift = (uintptr_t)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 
58 static 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 	unsigned int 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 = (uintptr_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 
102 int 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