drivers: introduce mtdblock abstraction

MTD block - abstraction over MTD subsystem, allowing
to read and write in blocks using BLK UCLASS.

Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>

drivers/block/blk-uclass.c

@@ -36,6 +36,7 @@ static struct {
 	{ UCLASS_PVBLOCK, "pvblock" },
 	{ UCLASS_BLKMAP, "blkmap" },
 	{ UCLASS_RKMTD, "rkmtd" },
+	{ UCLASS_MTD, "mtd" },
 };
 
 static enum uclass_id uclass_name_to_iftype(const char *uclass_idname)

drivers/mtd/Kconfig

@@ -32,6 +32,14 @@ config MTD_CONCAT
 	  into a single logical device. The larger logical device can then
 	  be partitioned.
 
+config MTD_BLOCK
+	bool "Enable block device access to MTD devices"
+	depends on BLK
+	default n
+	help
+	  Enable support for block device access to MTD devices
+	  using blk_ops abstraction.
+
 config SYS_MTDPARTS_RUNTIME
 	bool "Allow MTDPARTS to be configured at runtime"
 	help

drivers/mtd/Makefile

@@ -26,6 +26,7 @@ obj-y += onenand/
 obj-y += spi/
 obj-$(CONFIG_MTD_UBI) += ubi/
 obj-$(CONFIG_NVMXIP) += nvmxip/
+obj-$(CONFIG_MTD_BLOCK) += mtdblock.o
 
 #SPL/TPL build
 else

drivers/mtd/mtdblock.c

@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * MTD block - abstraction over MTD subsystem, allowing
+ * to read and write in blocks using BLK UCLASS.
+ *
+ * - Read algorithm:
+ *
+ *   1. Convert start block number to start address.
+ *   2. Read block_dev->blksz bytes using mtd_read() and
+ *      add to start address pointer block_dev->blksz bytes,
+ *      until the requested number of blocks have been read.
+ *
+ * - Write algorithm:
+ *
+ *   1. Convert start block number to start address.
+ *   2. Round this address down by mtd->erasesize.
+ *
+ *   Erase addr      Start addr
+ *      |                |
+ *      v                v
+ *      +----------------+----------------+----------------+
+ *      |     blksz      |      blksz     |      blksz     |
+ *      +----------------+----------------+----------------+
+ *
+ *   3. Calculate offset between this two addresses.
+ *   4. Read mtd->erasesize bytes using mtd_read() into
+ *      temporary buffer from erase address.
+ *
+ *   Erase addr      Start addr
+ *      |                |
+ *      v                v
+ *      +----------------+----------------+----------------+
+ *      |     blksz      |      blksz     |      blksz     |
+ *      +----------------+----------------+----------------+
+ *      ^
+ *      |
+ *      |
+ *   mtd_read()
+ *   from here
+ *
+ *   5. Copy data from user buffer to temporary buffer with offset,
+ *      calculated at step 3.
+ *   6. Erase and write mtd->erasesize bytes at erase address
+ *      pointer using mtd_erase/mtd_write().
+ *   7. Add to erase address pointer mtd->erasesize bytes.
+ *   8. goto 1 until the requested number of blocks have
+ *      been written.
+ *
+ * (C) Copyright 2024 SaluteDevices, Inc.
+ *
+ * Author: Alexey Romanov <avromanov@salutedevices.com>
+ */
+
+#include <blk.h>
+#include <part.h>
+#include <dm/device.h>
+#include <dm/device-internal.h>
+#include <linux/mtd/mtd.h>
+
+int mtd_bind(struct udevice *dev, struct mtd_info **mtd)
+{
+	struct blk_desc *bdesc;
+	struct udevice *bdev;
+	int ret;
+
+	ret = blk_create_devicef(dev, "mtd_blk", "blk", UCLASS_MTD,
+				 -1, 512, 0, &bdev);
+	if (ret) {
+		pr_err("Cannot create block device\n");
+		return ret;
+	}
+
+	bdesc = dev_get_uclass_plat(bdev);
+	dev_set_priv(bdev, mtd);
+	bdesc->bdev = bdev;
+	bdesc->part_type = PART_TYPE_MTD;
+
+	return 0;
+}
+
+static ulong mtd_blk_read(struct udevice *dev, lbaint_t start, lbaint_t blkcnt,
+			  void *dst)
+{
+	struct blk_desc *block_dev = dev_get_uclass_plat(dev);
+	struct mtd_info *mtd = blk_desc_to_mtd(block_dev);
+	unsigned int sect_size = block_dev->blksz;
+	lbaint_t cur = start;
+	ulong read_cnt = 0;
+
+	while (read_cnt < blkcnt) {
+		int ret;
+		loff_t sect_start = cur * sect_size;
+		size_t retlen;
+
+		ret = mtd_read(mtd, sect_start, sect_size, &retlen, dst);
+		if (ret)
+			return ret;
+
+		if (retlen != sect_size) {
+			pr_err("mtdblock: failed to read block 0x" LBAF "\n", cur);
+			return -EIO;
+		}
+
+		cur++;
+		dst += sect_size;
+		read_cnt++;
+	}
+
+	return read_cnt;
+}
+
+static int mtd_erase_write(struct mtd_info *mtd, uint64_t start, const void *src)
+{
+	int ret;
+	size_t retlen;
+	struct erase_info erase = { 0 };
+
+	erase.mtd = mtd;
+	erase.addr = start;
+	erase.len = mtd->erasesize;
+
+	ret = mtd_erase(mtd, &erase);
+	if (ret)
+		return ret;
+
+	ret = mtd_write(mtd, start, mtd->erasesize, &retlen, src);
+	if (ret)
+		return ret;
+
+	if (retlen != mtd->erasesize) {
+		pr_err("mtdblock: failed to read block at 0x%llx\n", start);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static ulong mtd_blk_write(struct udevice *dev, lbaint_t start, lbaint_t blkcnt,
+			   const void *src)
+{
+	struct blk_desc *block_dev = dev_get_uclass_plat(dev);
+	struct mtd_info *mtd = blk_desc_to_mtd(block_dev);
+	unsigned int sect_size = block_dev->blksz;
+	lbaint_t cur = start, blocks_todo = blkcnt;
+	ulong write_cnt = 0;
+	u8 *buf;
+	int ret = 0;
+
+	buf = malloc(mtd->erasesize);
+	if (!buf)
+		return -ENOMEM;
+
+	while (blocks_todo > 0) {
+		loff_t sect_start = cur * sect_size;
+		loff_t erase_start = ALIGN_DOWN(sect_start, mtd->erasesize);
+		u32 offset = sect_start - erase_start;
+		size_t cur_size = min_t(size_t,  mtd->erasesize - offset,
+					blocks_todo * sect_size);
+		size_t retlen;
+		lbaint_t written;
+
+		ret = mtd_read(mtd, erase_start, mtd->erasesize, &retlen, buf);
+		if (ret)
+			goto out;
+
+		if (retlen != mtd->erasesize) {
+			pr_err("mtdblock: failed to read block 0x" LBAF "\n", cur);
+			ret = -EIO;
+			goto out;
+		}
+
+		memcpy(buf + offset, src, cur_size);
+
+		ret = mtd_erase_write(mtd, erase_start, buf);
+		if (ret)
+			goto out;
+
+		written = cur_size / sect_size;
+
+		blocks_todo -= written;
+		cur += written;
+		src += cur_size;
+		write_cnt += written;
+	}
+
+out:
+	free(buf);
+
+	if (ret)
+		return ret;
+
+	return write_cnt;
+}
+
+static int mtd_blk_probe(struct udevice *dev)
+{
+	struct blk_desc *bdesc;
+	struct mtd_info *mtd;
+	int ret;
+
+	ret = device_probe(dev);
+	if (ret) {
+		pr_err("Probing %s failed (err=%d)\n", dev->name, ret);
+		return ret;
+	}
+
+	bdesc = dev_get_uclass_plat(dev);
+	mtd = blk_desc_to_mtd(bdesc);
+
+	if (mtd_type_is_nand(mtd))
+		pr_warn("MTD device '%s' is NAND, please use UBI devices instead\n",
+			mtd->name);
+
+	return 0;
+}
+
+static const struct blk_ops mtd_blk_ops = {
+	.read = mtd_blk_read,
+	.write = mtd_blk_write,
+};
+
+U_BOOT_DRIVER(mtd_blk) = {
+	.name = "mtd_blk",
+	.id = UCLASS_BLK,
+	.ops = &mtd_blk_ops,
+	.probe = mtd_blk_probe,
+};

include/linux/mtd/mtd.h

@@ -26,6 +26,7 @@
 #include <dm/device.h>
 #endif
 #include <dm/ofnode.h>
+#include <blk.h>
 
 #define MAX_MTD_DEVICES 32
 #endif
@@ -412,6 +413,30 @@ int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 		    const u_char *buf);
 
+#if CONFIG_IS_ENABLED(MTD_BLOCK)
+static inline struct mtd_info *blk_desc_to_mtd(struct blk_desc *bdesc)
+{
+	void *priv = dev_get_priv(bdesc->bdev);
+
+	if (!priv)
+		return NULL;
+
+	return *((struct mtd_info **)priv);
+}
+
+int mtd_bind(struct udevice *dev, struct mtd_info **mtd);
+#else
+static inline struct mtd_info *blk_desc_to_mtd(struct blk_desc *bdesc)
+{
+	return NULL;
+}
+
+static inline int mtd_bind(struct udevice *dev, struct mtd_info **mtd)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops);
 int mtd_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_oob_ops *ops);