181 lines
3.8 KiB
C
181 lines
3.8 KiB
C
// 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 void 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_bdev->bd_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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bio_io_error(bio);
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return;
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}
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pos += bvec.bv_len;
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}
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bio_endio(bio);
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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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int err = -ENOMEM;
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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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goto out;
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disk->first_minor = 0;
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disk->flags = GENHD_FL_NO_PART;
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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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err = add_disk(disk);
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if (err)
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goto out_cleanup_disk;
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pr_info("n64cart: %u kb disk\n", size / 1024);
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return 0;
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out_cleanup_disk:
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put_disk(disk);
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out:
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return err;
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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 <cand@gmx.com>");
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MODULE_DESCRIPTION("Driver for the N64 cart");
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MODULE_LICENSE("GPL");
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