n64cart.c 3.8 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180
  1. // SPDX-License-Identifier: GPL-2.0
  2. /*
  3. * Support for the N64 cart.
  4. *
  5. * Copyright (c) 2021 Lauri Kasanen
  6. */
  7. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  8. #include <linux/bitops.h>
  9. #include <linux/blkdev.h>
  10. #include <linux/dma-mapping.h>
  11. #include <linux/init.h>
  12. #include <linux/module.h>
  13. #include <linux/platform_device.h>
  14. enum {
  15. PI_DRAM_REG = 0,
  16. PI_CART_REG,
  17. PI_READ_REG,
  18. PI_WRITE_REG,
  19. PI_STATUS_REG,
  20. };
  21. #define PI_STATUS_DMA_BUSY (1 << 0)
  22. #define PI_STATUS_IO_BUSY (1 << 1)
  23. #define CART_DOMAIN 0x10000000
  24. #define CART_MAX 0x1FFFFFFF
  25. #define MIN_ALIGNMENT 8
  26. static u32 __iomem *reg_base;
  27. static unsigned int start;
  28. module_param(start, uint, 0);
  29. MODULE_PARM_DESC(start, "Start address of the cart block data");
  30. static unsigned int size;
  31. module_param(size, uint, 0);
  32. MODULE_PARM_DESC(size, "Size of the cart block data, in bytes");
  33. static void n64cart_write_reg(const u8 reg, const u32 value)
  34. {
  35. writel(value, reg_base + reg);
  36. }
  37. static u32 n64cart_read_reg(const u8 reg)
  38. {
  39. return readl(reg_base + reg);
  40. }
  41. static void n64cart_wait_dma(void)
  42. {
  43. while (n64cart_read_reg(PI_STATUS_REG) &
  44. (PI_STATUS_DMA_BUSY | PI_STATUS_IO_BUSY))
  45. cpu_relax();
  46. }
  47. /*
  48. * Process a single bvec of a bio.
  49. */
  50. static bool n64cart_do_bvec(struct device *dev, struct bio_vec *bv, u32 pos)
  51. {
  52. dma_addr_t dma_addr;
  53. const u32 bstart = pos + start;
  54. /* Alignment check */
  55. WARN_ON_ONCE((bv->bv_offset & (MIN_ALIGNMENT - 1)) ||
  56. (bv->bv_len & (MIN_ALIGNMENT - 1)));
  57. dma_addr = dma_map_bvec(dev, bv, DMA_FROM_DEVICE, 0);
  58. if (dma_mapping_error(dev, dma_addr))
  59. return false;
  60. n64cart_wait_dma();
  61. n64cart_write_reg(PI_DRAM_REG, dma_addr);
  62. n64cart_write_reg(PI_CART_REG, (bstart | CART_DOMAIN) & CART_MAX);
  63. n64cart_write_reg(PI_WRITE_REG, bv->bv_len - 1);
  64. n64cart_wait_dma();
  65. dma_unmap_page(dev, dma_addr, bv->bv_len, DMA_FROM_DEVICE);
  66. return true;
  67. }
  68. static void n64cart_submit_bio(struct bio *bio)
  69. {
  70. struct bio_vec bvec;
  71. struct bvec_iter iter;
  72. struct device *dev = bio->bi_bdev->bd_disk->private_data;
  73. u32 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT;
  74. bio_for_each_segment(bvec, bio, iter) {
  75. if (!n64cart_do_bvec(dev, &bvec, pos)) {
  76. bio_io_error(bio);
  77. return;
  78. }
  79. pos += bvec.bv_len;
  80. }
  81. bio_endio(bio);
  82. }
  83. static const struct block_device_operations n64cart_fops = {
  84. .owner = THIS_MODULE,
  85. .submit_bio = n64cart_submit_bio,
  86. };
  87. /*
  88. * The target device is embedded and RAM-constrained. We save RAM
  89. * by initializing in __init code that gets dropped late in boot.
  90. * For the same reason there is no module or unloading support.
  91. */
  92. static int __init n64cart_probe(struct platform_device *pdev)
  93. {
  94. struct gendisk *disk;
  95. int err = -ENOMEM;
  96. if (!start || !size) {
  97. pr_err("start or size not specified\n");
  98. return -ENODEV;
  99. }
  100. if (size & 4095) {
  101. pr_err("size must be a multiple of 4K\n");
  102. return -ENODEV;
  103. }
  104. reg_base = devm_platform_ioremap_resource(pdev, 0);
  105. if (IS_ERR(reg_base))
  106. return PTR_ERR(reg_base);
  107. disk = blk_alloc_disk(NUMA_NO_NODE);
  108. if (!disk)
  109. goto out;
  110. disk->first_minor = 0;
  111. disk->flags = GENHD_FL_NO_PART;
  112. disk->fops = &n64cart_fops;
  113. disk->private_data = &pdev->dev;
  114. strcpy(disk->disk_name, "n64cart");
  115. set_capacity(disk, size >> SECTOR_SHIFT);
  116. set_disk_ro(disk, 1);
  117. blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
  118. blk_queue_physical_block_size(disk->queue, 4096);
  119. blk_queue_logical_block_size(disk->queue, 4096);
  120. err = add_disk(disk);
  121. if (err)
  122. goto out_cleanup_disk;
  123. pr_info("n64cart: %u kb disk\n", size / 1024);
  124. return 0;
  125. out_cleanup_disk:
  126. put_disk(disk);
  127. out:
  128. return err;
  129. }
  130. static struct platform_driver n64cart_driver = {
  131. .driver = {
  132. .name = "n64cart",
  133. },
  134. };
  135. static int __init n64cart_init(void)
  136. {
  137. return platform_driver_probe(&n64cart_driver, n64cart_probe);
  138. }
  139. module_init(n64cart_init);
  140. MODULE_AUTHOR("Lauri Kasanen <[email protected]>");
  141. MODULE_DESCRIPTION("Driver for the N64 cart");
  142. MODULE_LICENSE("GPL");