1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Support for the N64 cart. 4 * 5 * Copyright (c) 2021 Lauri Kasanen 6 */ 7 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 15 MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>"); 16 MODULE_DESCRIPTION("Driver for the N64 cart"); 17 MODULE_LICENSE("GPL"); 18 19 static unsigned int start, size; 20 static u32 __iomem *reg_base; 21 static struct device *dev; 22 23 #define PI_DRAM_REG 0 24 #define PI_CART_REG 1 25 #define PI_READ_REG 2 26 #define PI_WRITE_REG 3 27 #define PI_STATUS_REG 4 28 29 #define PI_STATUS_DMA_BUSY (1 << 0) 30 #define PI_STATUS_IO_BUSY (1 << 1) 31 32 #define CART_DOMAIN 0x10000000 33 #define CART_MAX 0x1FFFFFFF 34 35 #define MIN_ALIGNMENT 8 36 37 static void n64cart_write_reg(const u8 reg, const u32 value) 38 { 39 writel(value, reg_base + reg); 40 } 41 42 static u32 n64cart_read_reg(const u8 reg) 43 { 44 return readl(reg_base + reg); 45 } 46 47 static void n64cart_wait_dma(void) 48 { 49 while (n64cart_read_reg(PI_STATUS_REG) & 50 (PI_STATUS_DMA_BUSY | PI_STATUS_IO_BUSY)) 51 cpu_relax(); 52 } 53 54 /* 55 * Process a single bvec of a bio. 56 */ 57 static bool n64cart_do_bvec(struct device *dev, struct bio_vec *bv, u32 pos) 58 { 59 dma_addr_t dma_addr; 60 const u32 bstart = pos + start; 61 62 /* Alignment check */ 63 WARN_ON_ONCE((bv->bv_offset & (MIN_ALIGNMENT - 1)) || 64 (bv->bv_len & (MIN_ALIGNMENT - 1))); 65 66 dma_addr = dma_map_bvec(dev, bv, DMA_FROM_DEVICE, 0); 67 if (dma_mapping_error(dev, dma_addr)) 68 return false; 69 70 n64cart_wait_dma(); 71 72 n64cart_write_reg(PI_DRAM_REG, dma_addr + bv->bv_offset); 73 n64cart_write_reg(PI_CART_REG, (bstart | CART_DOMAIN) & CART_MAX); 74 n64cart_write_reg(PI_WRITE_REG, bv->bv_len - 1); 75 76 n64cart_wait_dma(); 77 78 dma_unmap_page(dev, dma_addr, bv->bv_len, DMA_FROM_DEVICE); 79 return true; 80 } 81 82 static blk_qc_t n64cart_submit_bio(struct bio *bio) 83 { 84 struct bio_vec bvec; 85 u32 pos; 86 struct bvec_iter iter; 87 88 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT; 89 90 bio_for_each_segment(bvec, bio, iter) { 91 if (!n64cart_do_bvec(dev, &bvec, pos)) 92 goto io_error; 93 pos += bvec.bv_len; 94 } 95 96 bio_endio(bio); 97 return BLK_QC_T_NONE; 98 io_error: 99 bio_io_error(bio); 100 return BLK_QC_T_NONE; 101 } 102 103 static const struct block_device_operations n64cart_fops = { 104 .owner = THIS_MODULE, 105 .submit_bio = n64cart_submit_bio, 106 }; 107 108 /* 109 * The target device is embedded and RAM-constrained. We save RAM 110 * by initializing in __init code that gets dropped late in boot. 111 * For the same reason there is no module or unloading support. 112 */ 113 static int __init n64cart_probe(struct platform_device *pdev) 114 { 115 int err; 116 struct request_queue *queue; 117 struct gendisk *disk; 118 119 if (!start || !size) { 120 pr_err("n64cart: start and size not specified\n"); 121 return -ENODEV; 122 } 123 124 if (size & 4095) { 125 pr_err("n64cart: size must be a multiple of 4K\n"); 126 return -ENODEV; 127 } 128 129 queue = blk_alloc_queue(NUMA_NO_NODE); 130 if (!queue) { 131 return -ENOMEM; 132 } 133 134 reg_base = devm_platform_ioremap_resource(pdev, 0); 135 if (!reg_base) { 136 err = -EINVAL; 137 goto fail_queue; 138 } 139 140 disk = alloc_disk(0); 141 if (!disk) { 142 err = -ENOMEM; 143 goto fail_queue; 144 } 145 146 dev = &pdev->dev; 147 148 disk->first_minor = 0; 149 disk->queue = queue; 150 disk->flags = GENHD_FL_NO_PART_SCAN | GENHD_FL_EXT_DEVT; 151 disk->fops = &n64cart_fops; 152 strcpy(disk->disk_name, "n64cart"); 153 154 set_capacity(disk, size / 512); 155 set_disk_ro(disk, 1); 156 157 blk_queue_flag_set(QUEUE_FLAG_NONROT, queue); 158 blk_queue_physical_block_size(queue, 4096); 159 blk_queue_logical_block_size(queue, 4096); 160 161 add_disk(disk); 162 163 pr_info("n64cart: %u kb disk\n", size / 1024); 164 165 return 0; 166 fail_queue: 167 blk_cleanup_queue(queue); 168 169 return err; 170 } 171 172 static struct platform_driver n64cart_driver = { 173 .driver = { 174 .name = "n64cart", 175 }, 176 }; 177 178 static int __init n64cart_init(void) 179 { 180 return platform_driver_probe(&n64cart_driver, n64cart_probe); 181 } 182 183 module_param(start, uint, 0); 184 MODULE_PARM_DESC(start, "Start address of the cart block data"); 185 186 module_param(size, uint, 0); 187 MODULE_PARM_DESC(size, "Size of the cart block data, in bytes"); 188 189 module_init(n64cart_init); 190