summaryrefslogtreecommitdiffstats
path: root/drivers/block/n64cart.c
blob: 4db9a8c244af5cd5a1bf1827fc806bc9a3696555 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
// SPDX-License-Identifier: GPL-2.0
/*
 * Support for the N64 cart.
 *
 * Copyright (c) 2021 Lauri Kasanen
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/bitops.h>
#include <linux/blkdev.h>
#include <linux/dma-mapping.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>

enum {
	PI_DRAM_REG = 0,
	PI_CART_REG,
	PI_READ_REG,
	PI_WRITE_REG,
	PI_STATUS_REG,
};

#define PI_STATUS_DMA_BUSY	(1 << 0)
#define PI_STATUS_IO_BUSY	(1 << 1)

#define CART_DOMAIN		0x10000000
#define CART_MAX		0x1FFFFFFF

#define MIN_ALIGNMENT		8

static u32 __iomem *reg_base;

static unsigned int start;
module_param(start, uint, 0);
MODULE_PARM_DESC(start, "Start address of the cart block data");

static unsigned int size;
module_param(size, uint, 0);
MODULE_PARM_DESC(size, "Size of the cart block data, in bytes");

static void n64cart_write_reg(const u8 reg, const u32 value)
{
	writel(value, reg_base + reg);
}

static u32 n64cart_read_reg(const u8 reg)
{
	return readl(reg_base + reg);
}

static void n64cart_wait_dma(void)
{
	while (n64cart_read_reg(PI_STATUS_REG) &
		(PI_STATUS_DMA_BUSY | PI_STATUS_IO_BUSY))
		cpu_relax();
}

/*
 * Process a single bvec of a bio.
 */
static bool n64cart_do_bvec(struct device *dev, struct bio_vec *bv, u32 pos)
{
	dma_addr_t dma_addr;
	const u32 bstart = pos + start;

	/* Alignment check */
	WARN_ON_ONCE((bv->bv_offset & (MIN_ALIGNMENT - 1)) ||
		     (bv->bv_len & (MIN_ALIGNMENT - 1)));

	dma_addr = dma_map_bvec(dev, bv, DMA_FROM_DEVICE, 0);
	if (dma_mapping_error(dev, dma_addr))
		return false;

	n64cart_wait_dma();

	n64cart_write_reg(PI_DRAM_REG, dma_addr);
	n64cart_write_reg(PI_CART_REG, (bstart | CART_DOMAIN) & CART_MAX);
	n64cart_write_reg(PI_WRITE_REG, bv->bv_len - 1);

	n64cart_wait_dma();

	dma_unmap_page(dev, dma_addr, bv->bv_len, DMA_FROM_DEVICE);
	return true;
}

static void n64cart_submit_bio(struct bio *bio)
{
	struct bio_vec bvec;
	struct bvec_iter iter;
	struct device *dev = bio->bi_disk->private_data;
	u32 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT;

	bio_for_each_segment(bvec, bio, iter) {
		if (!n64cart_do_bvec(dev, &bvec, pos)) {
			bio_io_error(bio);
			return;
		}
		pos += bvec.bv_len;
	}

	bio_endio(bio);
}

static const struct block_device_operations n64cart_fops = {
	.owner		= THIS_MODULE,
	.submit_bio	= n64cart_submit_bio,
};

/*
 * The target device is embedded and RAM-constrained. We save RAM
 * by initializing in __init code that gets dropped late in boot.
 * For the same reason there is no module or unloading support.
 */
static int __init n64cart_probe(struct platform_device *pdev)
{
	struct gendisk *disk;
	int err = -ENOMEM;

	if (!start || !size) {
		pr_err("start or size not specified\n");
		return -ENODEV;
	}

	if (size & 4095) {
		pr_err("size must be a multiple of 4K\n");
		return -ENODEV;
	}

	reg_base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(reg_base))
		return PTR_ERR(reg_base);

	disk = blk_alloc_disk(NUMA_NO_NODE);
	if (!disk)
		goto out;

	disk->first_minor = 0;
	disk->flags = GENHD_FL_NO_PART;
	disk->fops = &n64cart_fops;
	disk->private_data = &pdev->dev;
	strcpy(disk->disk_name, "n64cart");

	set_capacity(disk, size >> SECTOR_SHIFT);
	set_disk_ro(disk, 1);

	blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
	blk_queue_physical_block_size(disk->queue, 4096);
	blk_queue_logical_block_size(disk->queue, 4096);

	err = add_disk(disk);
	if (err)
		goto out_cleanup_disk;

	pr_info("n64cart: %u kb disk\n", size / 1024);

	return 0;

out_cleanup_disk:
	blk_cleanup_disk(disk);
out:
	return err;
}

static struct platform_driver n64cart_driver = {
	.driver = {
		.name = "n64cart",
	},
};

static int __init n64cart_init(void)
{
	return platform_driver_probe(&n64cart_driver, n64cart_probe);
}

module_init(n64cart_init);

MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>");
MODULE_DESCRIPTION("Driver for the N64 cart");
MODULE_LICENSE("GPL");