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174 lines
3.8 KiB
174 lines
3.8 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Support for the N64 cart. |
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* |
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* Copyright (c) 2021 Lauri Kasanen |
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*/ |
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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#include <linux/bitops.h> |
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#include <linux/blkdev.h> |
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#include <linux/dma-mapping.h> |
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#include <linux/init.h> |
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#include <linux/module.h> |
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#include <linux/platform_device.h> |
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enum { |
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PI_DRAM_REG = 0, |
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PI_CART_REG, |
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PI_READ_REG, |
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PI_WRITE_REG, |
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PI_STATUS_REG, |
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}; |
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#define PI_STATUS_DMA_BUSY (1 << 0) |
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#define PI_STATUS_IO_BUSY (1 << 1) |
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#define CART_DOMAIN 0x10000000 |
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#define CART_MAX 0x1FFFFFFF |
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#define MIN_ALIGNMENT 8 |
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static u32 __iomem *reg_base; |
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static unsigned int start; |
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module_param(start, uint, 0); |
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MODULE_PARM_DESC(start, "Start address of the cart block data"); |
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static unsigned int size; |
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module_param(size, uint, 0); |
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MODULE_PARM_DESC(size, "Size of the cart block data, in bytes"); |
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static void n64cart_write_reg(const u8 reg, const u32 value) |
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{ |
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writel(value, reg_base + reg); |
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} |
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static u32 n64cart_read_reg(const u8 reg) |
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{ |
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return readl(reg_base + reg); |
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} |
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static void n64cart_wait_dma(void) |
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{ |
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while (n64cart_read_reg(PI_STATUS_REG) & |
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(PI_STATUS_DMA_BUSY | PI_STATUS_IO_BUSY)) |
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cpu_relax(); |
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} |
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/* |
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* Process a single bvec of a bio. |
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*/ |
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static bool n64cart_do_bvec(struct device *dev, struct bio_vec *bv, u32 pos) |
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{ |
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dma_addr_t dma_addr; |
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const u32 bstart = pos + start; |
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/* Alignment check */ |
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WARN_ON_ONCE((bv->bv_offset & (MIN_ALIGNMENT - 1)) || |
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(bv->bv_len & (MIN_ALIGNMENT - 1))); |
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dma_addr = dma_map_bvec(dev, bv, DMA_FROM_DEVICE, 0); |
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if (dma_mapping_error(dev, dma_addr)) |
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return false; |
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n64cart_wait_dma(); |
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n64cart_write_reg(PI_DRAM_REG, dma_addr); |
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n64cart_write_reg(PI_CART_REG, (bstart | CART_DOMAIN) & CART_MAX); |
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n64cart_write_reg(PI_WRITE_REG, bv->bv_len - 1); |
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n64cart_wait_dma(); |
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dma_unmap_page(dev, dma_addr, bv->bv_len, DMA_FROM_DEVICE); |
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return true; |
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} |
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static blk_qc_t n64cart_submit_bio(struct bio *bio) |
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{ |
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struct bio_vec bvec; |
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struct bvec_iter iter; |
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struct device *dev = bio->bi_disk->private_data; |
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u32 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT; |
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bio_for_each_segment(bvec, bio, iter) { |
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if (!n64cart_do_bvec(dev, &bvec, pos)) |
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goto io_error; |
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pos += bvec.bv_len; |
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} |
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bio_endio(bio); |
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return BLK_QC_T_NONE; |
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io_error: |
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bio_io_error(bio); |
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return BLK_QC_T_NONE; |
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} |
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static const struct block_device_operations n64cart_fops = { |
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.owner = THIS_MODULE, |
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.submit_bio = n64cart_submit_bio, |
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}; |
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/* |
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* The target device is embedded and RAM-constrained. We save RAM |
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* by initializing in __init code that gets dropped late in boot. |
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* For the same reason there is no module or unloading support. |
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*/ |
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static int __init n64cart_probe(struct platform_device *pdev) |
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{ |
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struct gendisk *disk; |
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if (!start || !size) { |
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pr_err("start or size not specified\n"); |
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return -ENODEV; |
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} |
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if (size & 4095) { |
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pr_err("size must be a multiple of 4K\n"); |
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return -ENODEV; |
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} |
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reg_base = devm_platform_ioremap_resource(pdev, 0); |
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if (IS_ERR(reg_base)) |
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return PTR_ERR(reg_base); |
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disk = blk_alloc_disk(NUMA_NO_NODE); |
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if (!disk) |
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return -ENOMEM; |
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disk->first_minor = 0; |
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disk->flags = GENHD_FL_NO_PART_SCAN; |
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disk->fops = &n64cart_fops; |
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disk->private_data = &pdev->dev; |
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strcpy(disk->disk_name, "n64cart"); |
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set_capacity(disk, size >> SECTOR_SHIFT); |
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set_disk_ro(disk, 1); |
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blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue); |
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blk_queue_physical_block_size(disk->queue, 4096); |
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blk_queue_logical_block_size(disk->queue, 4096); |
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add_disk(disk); |
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pr_info("n64cart: %u kb disk\n", size / 1024); |
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return 0; |
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} |
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static struct platform_driver n64cart_driver = { |
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.driver = { |
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.name = "n64cart", |
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}, |
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}; |
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static int __init n64cart_init(void) |
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{ |
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return platform_driver_probe(&n64cart_driver, n64cart_probe); |
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} |
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module_init(n64cart_init); |
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MODULE_AUTHOR("Lauri Kasanen <[email protected]>"); |
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MODULE_DESCRIPTION("Driver for the N64 cart"); |
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MODULE_LICENSE("GPL");
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