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