cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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n64cart.c (3918B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Support for the N64 cart.
      4 *
      5 * Copyright (c) 2021 Lauri Kasanen
      6 */
      7
      8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
      9#include <linux/bitops.h>
     10#include <linux/blkdev.h>
     11#include <linux/dma-mapping.h>
     12#include <linux/init.h>
     13#include <linux/module.h>
     14#include <linux/platform_device.h>
     15
     16enum {
     17	PI_DRAM_REG = 0,
     18	PI_CART_REG,
     19	PI_READ_REG,
     20	PI_WRITE_REG,
     21	PI_STATUS_REG,
     22};
     23
     24#define PI_STATUS_DMA_BUSY	(1 << 0)
     25#define PI_STATUS_IO_BUSY	(1 << 1)
     26
     27#define CART_DOMAIN		0x10000000
     28#define CART_MAX		0x1FFFFFFF
     29
     30#define MIN_ALIGNMENT		8
     31
     32static u32 __iomem *reg_base;
     33
     34static unsigned int start;
     35module_param(start, uint, 0);
     36MODULE_PARM_DESC(start, "Start address of the cart block data");
     37
     38static unsigned int size;
     39module_param(size, uint, 0);
     40MODULE_PARM_DESC(size, "Size of the cart block data, in bytes");
     41
     42static void n64cart_write_reg(const u8 reg, const u32 value)
     43{
     44	writel(value, reg_base + reg);
     45}
     46
     47static u32 n64cart_read_reg(const u8 reg)
     48{
     49	return readl(reg_base + reg);
     50}
     51
     52static void n64cart_wait_dma(void)
     53{
     54	while (n64cart_read_reg(PI_STATUS_REG) &
     55		(PI_STATUS_DMA_BUSY | PI_STATUS_IO_BUSY))
     56		cpu_relax();
     57}
     58
     59/*
     60 * Process a single bvec of a bio.
     61 */
     62static bool n64cart_do_bvec(struct device *dev, struct bio_vec *bv, u32 pos)
     63{
     64	dma_addr_t dma_addr;
     65	const u32 bstart = pos + start;
     66
     67	/* Alignment check */
     68	WARN_ON_ONCE((bv->bv_offset & (MIN_ALIGNMENT - 1)) ||
     69		     (bv->bv_len & (MIN_ALIGNMENT - 1)));
     70
     71	dma_addr = dma_map_bvec(dev, bv, DMA_FROM_DEVICE, 0);
     72	if (dma_mapping_error(dev, dma_addr))
     73		return false;
     74
     75	n64cart_wait_dma();
     76
     77	n64cart_write_reg(PI_DRAM_REG, dma_addr);
     78	n64cart_write_reg(PI_CART_REG, (bstart | CART_DOMAIN) & CART_MAX);
     79	n64cart_write_reg(PI_WRITE_REG, bv->bv_len - 1);
     80
     81	n64cart_wait_dma();
     82
     83	dma_unmap_page(dev, dma_addr, bv->bv_len, DMA_FROM_DEVICE);
     84	return true;
     85}
     86
     87static void n64cart_submit_bio(struct bio *bio)
     88{
     89	struct bio_vec bvec;
     90	struct bvec_iter iter;
     91	struct device *dev = bio->bi_bdev->bd_disk->private_data;
     92	u32 pos = bio->bi_iter.bi_sector << SECTOR_SHIFT;
     93
     94	bio_for_each_segment(bvec, bio, iter) {
     95		if (!n64cart_do_bvec(dev, &bvec, pos)) {
     96			bio_io_error(bio);
     97			return;
     98		}
     99		pos += bvec.bv_len;
    100	}
    101
    102	bio_endio(bio);
    103}
    104
    105static const struct block_device_operations n64cart_fops = {
    106	.owner		= THIS_MODULE,
    107	.submit_bio	= n64cart_submit_bio,
    108};
    109
    110/*
    111 * The target device is embedded and RAM-constrained. We save RAM
    112 * by initializing in __init code that gets dropped late in boot.
    113 * For the same reason there is no module or unloading support.
    114 */
    115static int __init n64cart_probe(struct platform_device *pdev)
    116{
    117	struct gendisk *disk;
    118	int err = -ENOMEM;
    119
    120	if (!start || !size) {
    121		pr_err("start or size not specified\n");
    122		return -ENODEV;
    123	}
    124
    125	if (size & 4095) {
    126		pr_err("size must be a multiple of 4K\n");
    127		return -ENODEV;
    128	}
    129
    130	reg_base = devm_platform_ioremap_resource(pdev, 0);
    131	if (IS_ERR(reg_base))
    132		return PTR_ERR(reg_base);
    133
    134	disk = blk_alloc_disk(NUMA_NO_NODE);
    135	if (!disk)
    136		goto out;
    137
    138	disk->first_minor = 0;
    139	disk->flags = GENHD_FL_NO_PART;
    140	disk->fops = &n64cart_fops;
    141	disk->private_data = &pdev->dev;
    142	strcpy(disk->disk_name, "n64cart");
    143
    144	set_capacity(disk, size >> SECTOR_SHIFT);
    145	set_disk_ro(disk, 1);
    146
    147	blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
    148	blk_queue_physical_block_size(disk->queue, 4096);
    149	blk_queue_logical_block_size(disk->queue, 4096);
    150
    151	err = add_disk(disk);
    152	if (err)
    153		goto out_cleanup_disk;
    154
    155	pr_info("n64cart: %u kb disk\n", size / 1024);
    156
    157	return 0;
    158
    159out_cleanup_disk:
    160	blk_cleanup_disk(disk);
    161out:
    162	return err;
    163}
    164
    165static struct platform_driver n64cart_driver = {
    166	.driver = {
    167		.name = "n64cart",
    168	},
    169};
    170
    171static int __init n64cart_init(void)
    172{
    173	return platform_driver_probe(&n64cart_driver, n64cart_probe);
    174}
    175
    176module_init(n64cart_init);
    177
    178MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>");
    179MODULE_DESCRIPTION("Driver for the N64 cart");
    180MODULE_LICENSE("GPL");