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// 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_bdev->bd_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 queue_limits lim = {
.physical_block_size = 4096,
.logical_block_size = 4096,
};
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(&lim, NUMA_NO_NODE);
if (IS_ERR(disk)) {
err = PTR_ERR(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);
err = add_disk(disk);
if (err)
goto out_cleanup_disk;
pr_info("n64cart: %u kb disk\n", size / 1024);
return 0;
out_cleanup_disk:
put_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");
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