SPI驱动程序设计

一、SPI驱动子系统架构

m25p80.c:

1. static int __devinit m25p_probe(struct spi_device *spi)
2. {
3. struct flash_platform_data    *data;
4. struct m25p            *flash;
5. struct flash_info        *info;
6. unsigned            i;
7. data = spi->dev.platform_data;
8. if (data && data->type) {                                       //配对设备，在m25p_data中找是否有对应的ID
9. for (i = 0, info = m25p_data;
10. i < ARRAY_SIZE(m25p_data);
11. i++, info++) {
12. if (strcmp(data->type, info->name) == 0)
13. break;
14. }
15. /* unrecognized chip? */                                   //芯片没有被认出
16. if (i == ARRAY_SIZE(m25p_data)) {
17. DEBUG(MTD_DEBUG_LEVEL0, "%s: unrecognized id %s\n",
18. dev_name(&spi->dev), data->type);
19. info = NULL;
20. /* recognized; is that chip really what's there? */                //找到芯片
21. } else if (info->jedec_id) {
22. struct flash_info    *chip = jedec_probe(spi);
23. if (!chip || chip != info) {
24. dev_warn(&spi->dev, "found %s, expected %s\n",
25. chip ? chip->name : "UNKNOWN",
26. info->name);
27. info = NULL;
28. }
29. }
30. } else
31. info = jedec_probe(spi);
32. if (!info)
33. return -ENODEV;
34. flash = kzalloc(sizeof *flash, GFP_KERNEL);                                    //分配空间
35. if (!flash)
36. return -ENOMEM;
37. flash->spi = spi;
38. mutex_init(&flash->lock);
39. dev_set_drvdata(&spi->dev, flash);
40. /*
41. * Atmel serial flash tend to power up
42. * with the software protection bits set
43. */
44. if (info->jedec_id >> 16 == 0x1f) {
45. write_enable(flash);
46. write_sr(flash, 0);
47. }
48. if (data && data->name)
49. flash->mtd.name = data->name;
50. else
51. flash->mtd.name = dev_name(&spi->dev);
52. flash->mtd.type = MTD_NORFLASH;                                                  //初始化操作集
53. flash->mtd.writesize = 1;
54. flash->mtd.flags = MTD_CAP_NORFLASH;
55. flash->mtd.size = info->sector_size * info->n_sectors;
56. flash->mtd.erase = m25p80_erase;
57. flash->mtd.read = m25p80_read;
58. flash->mtd.write = m25p80_write;
59. /* prefer "small sector" erase if possible */
60. if (info->flags & SECT_4K) {
61. flash->erase_opcode = OPCODE_BE_4K;
62. flash->mtd.erasesize = 4096;
63. } else {
64. flash->erase_opcode = OPCODE_SE;
65. flash->mtd.erasesize = info->sector_size;
66. }
67. flash->mtd.dev.parent = &spi->dev;
68. dev_info(&spi->dev, "%s (%lld Kbytes)\n", info->name,
69. (long long)flash->mtd.size >> 10);
70. DEBUG(MTD_DEBUG_LEVEL2,
71. "mtd .name = %s, .size = 0x%llx (%lldMiB) "
72. ".erasesize = 0x%.8x (%uKiB) .numeraseregions = %d\n",
73. flash->mtd.name,
74. (long long)flash->mtd.size, (long long)(flash->mtd.size >> 20),
75. flash->mtd.erasesize, flash->mtd.erasesize / 1024,
76. flash->mtd.numeraseregions);
77. if (flash->mtd.numeraseregions)
78. for (i = 0; i < flash->mtd.numeraseregions; i++)
79. DEBUG(MTD_DEBUG_LEVEL2,
80. "mtd.eraseregions[%d] = { .offset = 0x%llx, "
81. ".erasesize = 0x%.8x (%uKiB), "
82. ".numblocks = %d }\n",
83. i, (long long)flash->mtd.eraseregions[i].offset,
84. flash->mtd.eraseregions[i].erasesize,
85. flash->mtd.eraseregions[i].erasesize / 1024,
86. flash->mtd.eraseregions[i].numblocks);
87. /* partitions should match sector boundaries; and it may be good to
88. * use readonly partitions for writeprotected sectors (BP2..BP0).
89. */
90. if (mtd_has_partitions()) {
91. struct mtd_partition    *parts = NULL;
92. int            nr_parts = 0;
93. if (mtd_has_cmdlinepart()) {
94. static const char *part_probes[]
95. = { "cmdlinepart", NULL, };
96. nr_parts = parse_mtd_partitions(&flash->mtd,
97. part_probes, &parts, 0);
98. }
99. if (nr_parts <= 0 && data && data->parts) {
100. parts = data->parts;
101. nr_parts = data->nr_parts;
102. }
103. if (nr_parts > 0) {
104. for (i = 0; i < nr_parts; i++) {
105. DEBUG(MTD_DEBUG_LEVEL2, "partitions[%d] = "
106. "{.name = %s, .offset = 0x%llx, "
107. ".size = 0x%llx (%lldKiB) }\n",
108. i, parts[i].name,
109. (long long)parts[i].offset,
110. (long long)parts[i].size,
111. (long long)(parts[i].size >> 10));
112. }
113. flash->partitioned = 1;
114. return add_mtd_partitions(&flash->mtd, parts, nr_parts);
115. }
116. } else if (data->nr_parts)
117. dev_warn(&spi->dev, "ignoring %d default partitions on %s\n",
118. data->nr_parts, data->name);
119. return add_mtd_device(&flash->mtd) == 1 ? -ENODEV : 0;
120. }

m25p_write:

1. static int m25p80_write(struct mtd_info *mtd, loff_t to, size_t len,
2. size_t *retlen, const u_char *buf)
3. {
4. struct m25p *flash = mtd_to_m25p(mtd);
5. u32 page_offset, page_size;
6. struct spi_transfer t[2];                                                  //重要结构，一次发送
7. struct spi_message m;                                                      //重要结构，消息结构
8. DEBUG(MTD_DEBUG_LEVEL2, "%s: %s %s 0x%08x, len %zd\n",
9. dev_name(&flash->spi->dev), __func__, "to",
10. (u32)to, len);
11. if (retlen)
12. *retlen = 0;
13. /* sanity checks */
14. if (!len)
15. return(0);
16. if (to + len > flash->mtd.size)
17. return -EINVAL;
18. spi_message_init(&m);                                                  //这边进行了初始化
19. memset(t, 0, (sizeof t));                                              //清空
20. t[0].tx_buf = flash->command;
21. t[0].len = CMD_SIZE;
22. spi_message_add_tail(&t[0], &m);                                       //把数据挂汲取
23. t[1].tx_buf = buf;
24. spi_message_add_tail(&t[1], &m);
25. mutex_lock(&flash->lock);
26. /* Wait until finished previous write command. */
27. if (wait_till_ready(flash)) {
28. mutex_unlock(&flash->lock);
29. return 1;
30. }
31. write_enable(flash);
32. /* Set up the opcode in the write buffer. */                            //数据发送
33. flash->command[0] = OPCODE_PP;
34. flash->command[1] = to >> 16;
35. flash->command[2] = to >> 8;
36. flash->command[3] = to;
37. /* what page do we start with? */
38. page_offset = to % FLASH_PAGESIZE;
39. /* do all the bytes fit onto one page? */
40. if (page_offset + len <= FLASH_PAGESIZE) {
41. t[1].len = len;
42. spi_sync(flash->spi, &m);                                            //把message提交给控制器
43. *retlen = m.actual_length - CMD_SIZE;
44. } else {
45. u32 i;
46. /* the size of data remaining on the first page */
47. page_size = FLASH_PAGESIZE - page_offset;
48. t[1].len = page_size;
49. spi_sync(flash->spi, &m);
50. *retlen = m.actual_length - CMD_SIZE;
51. /* write everything in PAGESIZE chunks */
52. for (i = page_size; i < len; i += page_size) {
53. page_size = len - i;
54. if (page_size > FLASH_PAGESIZE)
55. page_size = FLASH_PAGESIZE;
56. /* write the next page to flash */
57. flash->command[1] = (to + i) >> 16;
58. flash->command[2] = (to + i) >> 8;
59. flash->command[3] = (to + i);
60. t[1].tx_buf = buf + i;
61. t[1].len = page_size;
62. wait_till_ready(flash);
63. write_enable(flash);
64. spi_sync(flash->spi, &m);
65. if (retlen)
66. *retlen += m.actual_length - CMD_SIZE;
67. }
68. }
69. mutex_unlock(&flash->lock);
70. return 0;
71. }

spi_master是SPI控制器，其中的queue把spi_message串成链表。这是一次SPI事务，而一个事务又分成一个一个的读写发送操作（spi_transfer）。