| // 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 blk_qc_t 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)) |
| goto io_error; |
| pos += bvec.bv_len; |
| } |
| |
| bio_endio(bio); |
| return BLK_QC_T_NONE; |
| io_error: |
| bio_io_error(bio); |
| return BLK_QC_T_NONE; |
| } |
| |
| 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; |
| |
| 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 (!reg_base) |
| return -EINVAL; |
| |
| disk = blk_alloc_disk(NUMA_NO_NODE); |
| if (!disk) |
| return -ENOMEM; |
| |
| disk->first_minor = 0; |
| disk->flags = GENHD_FL_NO_PART_SCAN; |
| 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); |
| |
| add_disk(disk); |
| |
| pr_info("n64cart: %u kb disk\n", size / 1024); |
| |
| return 0; |
| } |
| |
| 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"); |