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   */
bt1_rom_map_read(struct map_info * map,unsigned long ofs)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  
bt1_rom_map_copy_from(struct map_info * map,void * to,unsigned long from,ssize_t len)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  
of_flash_probe_bt1_rom(struct platform_device * pdev,struct device_node * np,struct map_info * map)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