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 blk_qc_t n64cart_submit_bio(struct bio *bio) 88 { 89 struct bio_vec bvec; 90 struct bvec_iter iter; 91 struct device *dev = bio->bi_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 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 struct gendisk *disk; 120 121 if (!start || !size) { 122 pr_err("start or size not specified\n"); 123 return -ENODEV; 124 } 125 126 if (size & 4095) { 127 pr_err("size must be a multiple of 4K\n"); 128 return -ENODEV; 129 } 130 131 reg_base = devm_platform_ioremap_resource(pdev, 0); 132 if (!reg_base) 133 return -EINVAL; 134 135 disk = blk_alloc_disk(NUMA_NO_NODE); 136 if (!disk) 137 return -ENOMEM; 138 139 disk->first_minor = 0; 140 disk->flags = GENHD_FL_NO_PART_SCAN; 141 disk->fops = &n64cart_fops; 142 disk->private_data = &pdev->dev; 143 strcpy(disk->disk_name, "n64cart"); 144 145 set_capacity(disk, size >> SECTOR_SHIFT); 146 set_disk_ro(disk, 1); 147 148 blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue); 149 blk_queue_physical_block_size(disk->queue, 4096); 150 blk_queue_logical_block_size(disk->queue, 4096); 151 152 add_disk(disk); 153 154 pr_info("n64cart: %u kb disk\n", size / 1024); 155 156 return 0; 157 } 158 159 static struct platform_driver n64cart_driver = { 160 .driver = { 161 .name = "n64cart", 162 }, 163 }; 164 165 static int __init n64cart_init(void) 166 { 167 return platform_driver_probe(&n64cart_driver, n64cart_probe); 168 } 169 170 module_init(n64cart_init); 171 172 MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>"); 173 MODULE_DESCRIPTION("Driver for the N64 cart"); 174 MODULE_LICENSE("GPL"); 175