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 #define PI_DRAM_REG 0 17 #define PI_CART_REG 1 18 #define PI_READ_REG 2 19 #define PI_WRITE_REG 3 20 #define PI_STATUS_REG 4 21 22 #define PI_STATUS_DMA_BUSY (1 << 0) 23 #define PI_STATUS_IO_BUSY (1 << 1) 24 25 #define CART_DOMAIN 0x10000000 26 #define CART_MAX 0x1FFFFFFF 27 28 #define MIN_ALIGNMENT 8 29 30 static u32 __iomem *reg_base; 31 static struct device *dev; 32 33 static unsigned int start; 34 module_param(start, uint, 0); 35 MODULE_PARM_DESC(start, "Start address of the cart block data"); 36 37 static unsigned int size; 38 module_param(size, uint, 0); 39 MODULE_PARM_DESC(size, "Size of the cart block data, in bytes"); 40 41 static void n64cart_write_reg(const u8 reg, const u32 value) 42 { 43 writel(value, reg_base + reg); 44 } 45 46 static u32 n64cart_read_reg(const u8 reg) 47 { 48 return readl(reg_base + reg); 49 } 50 51 static void n64cart_wait_dma(void) 52 { 53 while (n64cart_read_reg(PI_STATUS_REG) & 54 (PI_STATUS_DMA_BUSY | PI_STATUS_IO_BUSY)) 55 cpu_relax(); 56 } 57 58 /* 59 * Process a single bvec of a bio. 60 */ 61 static bool n64cart_do_bvec(struct device *dev, struct bio_vec *bv, u32 pos) 62 { 63 dma_addr_t dma_addr; 64 const u32 bstart = pos + start; 65 66 /* Alignment check */ 67 WARN_ON_ONCE((bv->bv_offset & (MIN_ALIGNMENT - 1)) || 68 (bv->bv_len & (MIN_ALIGNMENT - 1))); 69 70 dma_addr = dma_map_bvec(dev, bv, DMA_FROM_DEVICE, 0); 71 if (dma_mapping_error(dev, dma_addr)) 72 return false; 73 74 n64cart_wait_dma(); 75 76 n64cart_write_reg(PI_DRAM_REG, dma_addr + bv->bv_offset); 77 n64cart_write_reg(PI_CART_REG, (bstart | CART_DOMAIN) & CART_MAX); 78 n64cart_write_reg(PI_WRITE_REG, bv->bv_len - 1); 79 80 n64cart_wait_dma(); 81 82 dma_unmap_page(dev, dma_addr, bv->bv_len, DMA_FROM_DEVICE); 83 return true; 84 } 85 86 static blk_qc_t n64cart_submit_bio(struct bio *bio) 87 { 88 struct bio_vec bvec; 89 u32 pos; 90 struct bvec_iter iter; 91 92 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT; 93 94 bio_for_each_segment(bvec, bio, iter) { 95 if (!n64cart_do_bvec(dev, &bvec, pos)) 96 goto io_error; 97 pos += bvec.bv_len; 98 } 99 100 bio_endio(bio); 101 return BLK_QC_T_NONE; 102 io_error: 103 bio_io_error(bio); 104 return BLK_QC_T_NONE; 105 } 106 107 static const struct block_device_operations n64cart_fops = { 108 .owner = THIS_MODULE, 109 .submit_bio = n64cart_submit_bio, 110 }; 111 112 /* 113 * The target device is embedded and RAM-constrained. We save RAM 114 * by initializing in __init code that gets dropped late in boot. 115 * For the same reason there is no module or unloading support. 116 */ 117 static int __init n64cart_probe(struct platform_device *pdev) 118 { 119 int err; 120 struct request_queue *queue; 121 struct gendisk *disk; 122 123 if (!start || !size) { 124 pr_err("start or size not specified\n"); 125 return -ENODEV; 126 } 127 128 if (size & 4095) { 129 pr_err("size must be a multiple of 4K\n"); 130 return -ENODEV; 131 } 132 133 queue = blk_alloc_queue(NUMA_NO_NODE); 134 if (!queue) { 135 return -ENOMEM; 136 } 137 138 reg_base = devm_platform_ioremap_resource(pdev, 0); 139 if (!reg_base) { 140 err = -EINVAL; 141 goto fail_queue; 142 } 143 144 disk = alloc_disk(0); 145 if (!disk) { 146 err = -ENOMEM; 147 goto fail_queue; 148 } 149 150 dev = &pdev->dev; 151 152 disk->first_minor = 0; 153 disk->queue = queue; 154 disk->flags = GENHD_FL_NO_PART_SCAN | GENHD_FL_EXT_DEVT; 155 disk->fops = &n64cart_fops; 156 strcpy(disk->disk_name, "n64cart"); 157 158 set_capacity(disk, size / 512); 159 set_disk_ro(disk, 1); 160 161 blk_queue_flag_set(QUEUE_FLAG_NONROT, queue); 162 blk_queue_physical_block_size(queue, 4096); 163 blk_queue_logical_block_size(queue, 4096); 164 165 add_disk(disk); 166 167 pr_info("n64cart: %u kb disk\n", size / 1024); 168 169 return 0; 170 fail_queue: 171 blk_cleanup_queue(queue); 172 173 return err; 174 } 175 176 static struct platform_driver n64cart_driver = { 177 .driver = { 178 .name = "n64cart", 179 }, 180 }; 181 182 static int __init n64cart_init(void) 183 { 184 return platform_driver_probe(&n64cart_driver, n64cart_probe); 185 } 186 187 module_init(n64cart_init); 188 189 MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>"); 190 MODULE_DESCRIPTION("Driver for the N64 cart"); 191 MODULE_LICENSE("GPL"); 192