1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Support for the N64 cart. 4 * 5 * Copyright (c) 2021 Lauri Kasanen 6 */ 7 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 #include <linux/bitops.h> 10 #include <linux/blkdev.h> 11 #include <linux/dma-mapping.h> 12 #include <linux/init.h> 13 #include <linux/module.h> 14 #include <linux/platform_device.h> 15 16 enum { 17 PI_DRAM_REG = 0, 18 PI_CART_REG, 19 PI_READ_REG, 20 PI_WRITE_REG, 21 PI_STATUS_REG, 22 }; 23 24 #define PI_STATUS_DMA_BUSY (1 << 0) 25 #define PI_STATUS_IO_BUSY (1 << 1) 26 27 #define CART_DOMAIN 0x10000000 28 #define CART_MAX 0x1FFFFFFF 29 30 #define MIN_ALIGNMENT 8 31 32 static u32 __iomem *reg_base; 33 static struct device *dev; 34 35 static unsigned int start; 36 module_param(start, uint, 0); 37 MODULE_PARM_DESC(start, "Start address of the cart block data"); 38 39 static unsigned int size; 40 module_param(size, uint, 0); 41 MODULE_PARM_DESC(size, "Size of the cart block data, in bytes"); 42 43 static void n64cart_write_reg(const u8 reg, const u32 value) 44 { 45 writel(value, reg_base + reg); 46 } 47 48 static u32 n64cart_read_reg(const u8 reg) 49 { 50 return readl(reg_base + reg); 51 } 52 53 static void n64cart_wait_dma(void) 54 { 55 while (n64cart_read_reg(PI_STATUS_REG) & 56 (PI_STATUS_DMA_BUSY | PI_STATUS_IO_BUSY)) 57 cpu_relax(); 58 } 59 60 /* 61 * Process a single bvec of a bio. 62 */ 63 static bool n64cart_do_bvec(struct device *dev, struct bio_vec *bv, u32 pos) 64 { 65 dma_addr_t dma_addr; 66 const u32 bstart = pos + start; 67 68 /* Alignment check */ 69 WARN_ON_ONCE((bv->bv_offset & (MIN_ALIGNMENT - 1)) || 70 (bv->bv_len & (MIN_ALIGNMENT - 1))); 71 72 dma_addr = dma_map_bvec(dev, bv, DMA_FROM_DEVICE, 0); 73 if (dma_mapping_error(dev, dma_addr)) 74 return false; 75 76 n64cart_wait_dma(); 77 78 n64cart_write_reg(PI_DRAM_REG, dma_addr + bv->bv_offset); 79 n64cart_write_reg(PI_CART_REG, (bstart | CART_DOMAIN) & CART_MAX); 80 n64cart_write_reg(PI_WRITE_REG, bv->bv_len - 1); 81 82 n64cart_wait_dma(); 83 84 dma_unmap_page(dev, dma_addr, bv->bv_len, DMA_FROM_DEVICE); 85 return true; 86 } 87 88 static blk_qc_t n64cart_submit_bio(struct bio *bio) 89 { 90 struct bio_vec bvec; 91 u32 pos; 92 struct bvec_iter iter; 93 94 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT; 95 96 bio_for_each_segment(bvec, bio, iter) { 97 if (!n64cart_do_bvec(dev, &bvec, pos)) 98 goto io_error; 99 pos += bvec.bv_len; 100 } 101 102 bio_endio(bio); 103 return BLK_QC_T_NONE; 104 io_error: 105 bio_io_error(bio); 106 return BLK_QC_T_NONE; 107 } 108 109 static const struct block_device_operations n64cart_fops = { 110 .owner = THIS_MODULE, 111 .submit_bio = n64cart_submit_bio, 112 }; 113 114 /* 115 * The target device is embedded and RAM-constrained. We save RAM 116 * by initializing in __init code that gets dropped late in boot. 117 * For the same reason there is no module or unloading support. 118 */ 119 static int __init n64cart_probe(struct platform_device *pdev) 120 { 121 int err; 122 struct request_queue *queue; 123 struct gendisk *disk; 124 125 if (!start || !size) { 126 pr_err("start or size not specified\n"); 127 return -ENODEV; 128 } 129 130 if (size & 4095) { 131 pr_err("size must be a multiple of 4K\n"); 132 return -ENODEV; 133 } 134 135 queue = blk_alloc_queue(NUMA_NO_NODE); 136 if (!queue) 137 return -ENOMEM; 138 139 reg_base = devm_platform_ioremap_resource(pdev, 0); 140 if (!reg_base) { 141 err = -EINVAL; 142 goto fail_queue; 143 } 144 145 disk = alloc_disk(0); 146 if (!disk) { 147 err = -ENOMEM; 148 goto fail_queue; 149 } 150 151 dev = &pdev->dev; 152 153 disk->first_minor = 0; 154 disk->queue = queue; 155 disk->flags = GENHD_FL_NO_PART_SCAN | GENHD_FL_EXT_DEVT; 156 disk->fops = &n64cart_fops; 157 strcpy(disk->disk_name, "n64cart"); 158 159 set_capacity(disk, size >> SECTOR_SHIFT); 160 set_disk_ro(disk, 1); 161 162 blk_queue_flag_set(QUEUE_FLAG_NONROT, queue); 163 blk_queue_physical_block_size(queue, 4096); 164 blk_queue_logical_block_size(queue, 4096); 165 166 add_disk(disk); 167 168 pr_info("n64cart: %u kb disk\n", size / 1024); 169 170 return 0; 171 fail_queue: 172 blk_cleanup_queue(queue); 173 174 return err; 175 } 176 177 static struct platform_driver n64cart_driver = { 178 .driver = { 179 .name = "n64cart", 180 }, 181 }; 182 183 static int __init n64cart_init(void) 184 { 185 return platform_driver_probe(&n64cart_driver, n64cart_probe); 186 } 187 188 module_init(n64cart_init); 189 190 MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>"); 191 MODULE_DESCRIPTION("Driver for the N64 cart"); 192 MODULE_LICENSE("GPL"); 193