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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 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:
- 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 <[email protected]>");
- MODULE_DESCRIPTION("Driver for the N64 cart");
- MODULE_LICENSE("GPL");
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