[PATCH v9] block: Add n64 cart driver

Lauri Kasanen
2021-01-22T12:36:30Z

This adds support for the Nintendo 64 console's carts. Carts are a
read-only media ranging from 8mb to 64mb.

Only one cart can be connected at once, and switching it requires a
reboot.

No module support to save RAM, as the target has 8mb RAM.

Signed-off-by: Lauri Kasanen <cand@gmx.com>
---
drivers/block/Kconfig | 6 ++
drivers/block/Makefile | 1 +
drivers/block/n64cart.c | 211 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 218 insertions(+)
create mode 100644 drivers/block/n64cart.c

v9:
cosmetics
min_t

v8:
SZ_64K
remove barriers
add defines for block domain constants
__blk_mq_end_request
remove register_blkdev via GENHD_FL_EXT_DEVT
dma_alloc_noncoherent, sync

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index ecceaaa..924d768 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -72,6 +72,12 @@ config AMIGA_Z2RAM
To compile this driver as a module, choose M here: the
module will be called z2ram.

+config N64CART
+ bool "N64 cart support"
+ depends on MACH_NINTENDO64
+ help
+ Support for the N64 cart.
+
config CDROM
tristate
select BLK_SCSI_REQUEST
diff --git a/drivers/block/Makefile b/drivers/block/Makefile
index e1f6311..b9642cf 100644
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_PS3_DISK) += ps3disk.o
obj-$(CONFIG_PS3_VRAM) += ps3vram.o
obj-$(CONFIG_ATARI_FLOPPY) += ataflop.o
obj-$(CONFIG_AMIGA_Z2RAM) += z2ram.o
+obj-$(CONFIG_N64CART) += n64cart.o
obj-$(CONFIG_BLK_DEV_RAM) += brd.o
obj-$(CONFIG_BLK_DEV_LOOP) += loop.o
obj-$(CONFIG_XILINX_SYSACE) += xsysace.o
diff --git a/drivers/block/n64cart.c b/drivers/block/n64cart.c
new file mode 100644
index 0000000..01dd008
--- /dev/null
+++ b/drivers/block/n64cart.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for the N64 cart.
+ *
+ * Copyright (c) 2021 Lauri Kasanen
+ */
+
+#include <linux/bitops.h>
+#include <linux/blk-mq.h>
+#include <linux/dma-mapping.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>");
+MODULE_DESCRIPTION("Driver for the N64 cart");
+MODULE_LICENSE("GPL");
+
+#define BUFSIZE SZ_64K
+
+static unsigned int start, size;
+static struct request_queue *queue;
+static struct blk_mq_tag_set tag_set;
+static struct gendisk *disk;
+
+static void *buf;
+static dma_addr_t dma_addr;
+
+static u32 __iomem *reg_base;
+
+#define PI_DRAM_REG 0
+#define PI_CART_REG 1
+#define PI_READ_REG 2
+#define PI_WRITE_REG 3
+#define PI_STATUS_REG 4
+
+#define PI_STATUS_DMA_BUSY (1 << 0)
+#define PI_STATUS_IO_BUSY (1 << 1)
+
+#define CART_DOMAIN 0x10000000
+#define CART_MAX 0x1FFFFFFF
+
+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();
+}
+
+static blk_status_t n64cart_get_seg(struct request *req)
+{
+ u32 bstart = blk_rq_pos(req) * 512;
+ u32 len = blk_rq_cur_bytes(req);
+ void *dst = bio_data(req->bio);
+
+ if (bstart + len > size)
+ return BLK_STS_IOERR;
+
+ bstart += start;
+
+ while (len) {
+ const u32 curlen = min_t(u32, len, BUFSIZE);
+
+ dma_sync_single_for_device(disk_to_dev(disk), dma_addr,
+ BUFSIZE, DMA_FROM_DEVICE);
+
+ 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, curlen - 1);
+
+ n64cart_wait_dma();
+
+ dma_sync_single_for_cpu(disk_to_dev(disk), dma_addr,
+ BUFSIZE, DMA_FROM_DEVICE);
+
+ memcpy(dst, buf, curlen);
+
+ len -= curlen;
+ dst += curlen;
+ bstart += curlen;
+ }
+
+ return BLK_STS_OK;
+}
+
+static blk_status_t n64cart_queue_rq(struct blk_mq_hw_ctx *hctx,
+ const struct blk_mq_queue_data *bd)
+{
+ struct request *req = bd->rq;
+ blk_status_t err;
+
+ blk_mq_start_request(req);
+
+ do {
+ err = n64cart_get_seg(req);
+ } while (blk_update_request(req, err, blk_rq_cur_bytes(req)));
+
+ __blk_mq_end_request(req, BLK_STS_OK);
+ return BLK_STS_OK;
+}
+
+static const struct blk_mq_ops n64cart_mq_ops = {
+ .queue_rq = n64cart_queue_rq,
+};
+
+static const struct block_device_operations n64cart_fops = {
+ .owner = THIS_MODULE,
+};
+
+/*
+ * 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)
+{
+ int err;
+
+ if (!start || !size) {
+ pr_err("n64cart: start and size not specified\n");
+ return -ENODEV;
+ }
+
+ if (size & 4095) {
+ pr_err("n64cart: size must be a multiple of 4K\n");
+ return -ENODEV;
+ }
+
+ queue = blk_mq_init_sq_queue(&tag_set, &n64cart_mq_ops, 1,
+ BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_BLOCKING);
+ if (IS_ERR(queue)) {
+ return PTR_ERR(queue);
+ }
+
+ buf = dma_alloc_noncoherent(&pdev->dev, BUFSIZE, &dma_addr,
+ DMA_FROM_DEVICE, GFP_KERNEL);
+ if (!buf) {
+ err = -ENOMEM;
+ goto fail_queue;
+ }
+
+ reg_base = devm_platform_ioremap_resource(pdev, 0);
+ if (!reg_base) {
+ err = -EINVAL;
+ goto fail_dma;
+ }
+
+ disk = alloc_disk(0);
+ if (!disk) {
+ err = -ENOMEM;
+ goto fail_dma;
+ }
+
+ disk->first_minor = 0;
+ disk->queue = queue;
+ disk->flags = GENHD_FL_NO_PART_SCAN | GENHD_FL_EXT_DEVT;
+ disk->fops = &n64cart_fops;
+ strcpy(disk->disk_name, "n64cart");
+
+ set_capacity(disk, size / 512);
+ set_disk_ro(disk, 1);
+
+ blk_queue_flag_set(QUEUE_FLAG_NONROT, queue);
+ blk_queue_physical_block_size(queue, 4096);
+ blk_queue_logical_block_size(queue, 4096);
+
+ add_disk(disk);
+
+ pr_info("n64cart: %u kb disk\n", size / 1024);
+
+ return 0;
+fail_dma:
+ dma_free_noncoherent(&pdev->dev, BUFSIZE, buf, dma_addr,
+ DMA_FROM_DEVICE);
+fail_queue:
+ blk_cleanup_queue(queue);
+
+ 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_param(start, uint, 0);
+MODULE_PARM_DESC(start, "Start address of the cart block data");
+
+module_param(size, uint, 0);
+MODULE_PARM_DESC(size, "Size of the cart block data, in bytes");
+
+module_init(n64cart_init);
--
2.6.2