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d9b2a2bb LK |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* | |
3 | * Support for the N64 cart. | |
4 | * | |
5 | * Copyright (c) 2021 Lauri Kasanen | |
6 | */ | |
7 | ||
f1e19224 | 8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
d9b2a2bb LK |
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 | ||
2ce503b3 CK |
16 | enum { |
17 | PI_DRAM_REG = 0, | |
18 | PI_CART_REG, | |
19 | PI_READ_REG, | |
20 | PI_WRITE_REG, | |
21 | PI_STATUS_REG, | |
22 | }; | |
d9b2a2bb LK |
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 | ||
e39e3132 | 32 | static u32 __iomem *reg_base; |
e39e3132 CK |
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 | ||
d9b2a2bb LK |
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 + bv->bv_offset); | |
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; | |
d9b2a2bb | 90 | struct bvec_iter iter; |
13d41b53 | 91 | struct device *dev = bio->bi_disk->private_data; |
37772f91 | 92 | u32 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT; |
d9b2a2bb LK |
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 | { | |
d9b2a2bb LK |
119 | struct gendisk *disk; |
120 | ||
121 | if (!start || !size) { | |
f1e19224 | 122 | pr_err("start or size not specified\n"); |
d9b2a2bb LK |
123 | return -ENODEV; |
124 | } | |
125 | ||
126 | if (size & 4095) { | |
f1e19224 | 127 | pr_err("size must be a multiple of 4K\n"); |
d9b2a2bb LK |
128 | return -ENODEV; |
129 | } | |
130 | ||
d9b2a2bb | 131 | reg_base = devm_platform_ioremap_resource(pdev, 0); |
0d424780 CK |
132 | if (!reg_base) |
133 | return -EINVAL; | |
d9b2a2bb | 134 | |
f9dc931d | 135 | disk = blk_alloc_disk(NUMA_NO_NODE); |
0d424780 CK |
136 | if (!disk) |
137 | return -ENOMEM; | |
138 | ||
d9b2a2bb | 139 | disk->first_minor = 0; |
0d1feb72 | 140 | disk->flags = GENHD_FL_NO_PART_SCAN; |
d9b2a2bb | 141 | disk->fops = &n64cart_fops; |
13d41b53 | 142 | disk->private_data = &pdev->dev; |
d9b2a2bb LK |
143 | strcpy(disk->disk_name, "n64cart"); |
144 | ||
857f6fde | 145 | set_capacity(disk, size >> SECTOR_SHIFT); |
d9b2a2bb LK |
146 | set_disk_ro(disk, 1); |
147 | ||
0d424780 CK |
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); | |
d9b2a2bb LK |
151 | |
152 | add_disk(disk); | |
153 | ||
154 | pr_info("n64cart: %u kb disk\n", size / 1024); | |
155 | ||
156 | return 0; | |
d9b2a2bb LK |
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 | ||
d9b2a2bb | 170 | module_init(n64cart_init); |
9ee8c9a1 CK |
171 | |
172 | MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>"); | |
173 | MODULE_DESCRIPTION("Driver for the N64 cart"); | |
174 | MODULE_LICENSE("GPL"); |