drivers/mtd/nvmxip: introduce NVM XIP block storage emulation

add block storage emulation for NVM XIP flash devices

Some paltforms such as Corstone-1000 need to see NVM XIP raw flash
as a block storage device with read only capability.

Here NVM flash devices are devices with addressable
memory (e.g: QSPI NOR flash).

The implementation is generic and can be used by different platforms.

Two drivers are provided as follows.

  nvmxip-blk :

    a generic block driver allowing to read from the XIP flash

  nvmxip Uclass driver :

        When a device is described in the DT and associated with
        UCLASS_NVMXIP, the Uclass creates a block device and binds it with
	 the nvmxip-blk.

Platforms can use multiple NVM XIP devices at the same time by defining a
DT node for each one of them.

Signed-off-by: Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>

MAINTAINERS

@@ -1204,6 +1204,12 @@ F:	cmd/nvme.c
 F:	include/nvme.h
 F:	doc/develop/driver-model/nvme.rst
 
+NVMXIP
+M:	Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
+S:	Maintained
+F:	doc/develop/driver-model/nvmxip.rst
+F:	drivers/mtd/nvmxip/
+
 NVMEM
 M:	Sean Anderson <seanga2@gmail.com>
 S:	Maintained

doc/develop/driver-model/index.rst

@@ -20,6 +20,7 @@ subsystems
    livetree
    migration
    nvme
+   nvmxip
    of-plat
    pci-info
    pmic-framework

doc/develop/driver-model/nvmxip.rst

@@ -0,0 +1,48 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+NVM XIP Block Storage Emulation Driver
+=======================================
+
+Summary
+-------
+
+Non-Volatile Memory devices with addressable memory (e.g: QSPI NOR flash) could
+be used for block storage needs (e.g: parsing a GPT layout in a raw QSPI NOR flash).
+
+The NVMXIP Uclass provides this functionality and can be used for any 64-bit platform.
+
+The NVMXIP Uclass provides the following drivers:
+
+      nvmxip-blk block driver:
+
+        A generic block driver allowing to read from the XIP flash.
+	The driver belongs to UCLASS_BLK.
+	The driver implemented by drivers/mtd/nvmxip/nvmxip.c
+
+      nvmxip Uclass driver:
+
+        When a device is described in the DT and associated with UCLASS_NVMXIP,
+        the Uclass creates a block device and binds it with the nvmxip-blk.
+	The Uclass driver implemented by drivers/mtd/nvmxip/nvmxip-uclass.c
+
+    The implementation is generic and can be used by different platforms.
+
+Supported hardware
+--------------------------------
+
+Any 64-bit plaform.
+
+Configuration
+----------------------
+
+config NVMXIP
+	  This option allows the emulation of a block storage device
+	  on top of a direct access non volatile memory XIP flash devices.
+	  This support provides the read operation.
+	  This option provides the block storage driver nvmxip-blk which
+	  handles the read operation. This driver is HW agnostic and can support
+	  multiple flash devices at the same time.
+
+Contributors
+------------
+   * Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>

drivers/block/blk-uclass.c

@@ -28,6 +28,7 @@ static struct {
 	{ UCLASS_AHCI, "sata" },
 	{ UCLASS_HOST, "host" },
 	{ UCLASS_NVME, "nvme" },
+	{ UCLASS_NVMXIP, "nvmxip" },
 	{ UCLASS_EFI_MEDIA, "efi" },
 	{ UCLASS_EFI_LOADER, "efiloader" },
 	{ UCLASS_VIRTIO, "virtio" },

drivers/mtd/Kconfig

@@ -270,4 +270,6 @@ source "drivers/mtd/spi/Kconfig"
 
 source "drivers/mtd/ubi/Kconfig"
 
+source "drivers/mtd/nvmxip/Kconfig"
+
 endmenu

drivers/mtd/Makefile

@@ -25,6 +25,7 @@ obj-y += nand/
 obj-y += onenand/
 obj-y += spi/
 obj-$(CONFIG_MTD_UBI) += ubi/
+obj-$(CONFIG_NVMXIP) += nvmxip/
 
 #SPL/TPL build
 else

drivers/mtd/nvmxip/Kconfig

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright 2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
+# Authors:
+#   Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
+
+config NVMXIP
+	bool "NVM XIP devices support"
+	select BLK
+	help
+	  This option allows the emulation of a block storage device
+	  on top of a direct access non volatile memory XIP flash devices.
+	  This support provides the read operation.

drivers/mtd/nvmxip/Makefile

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright 2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
+# Authors:
+#   Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
+
+obj-y += nvmxip-uclass.o nvmxip.o

drivers/mtd/nvmxip/nvmxip-uclass.c

@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
+ *
+ * Authors:
+ *   Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <log.h>
+#include <linux/bitops.h>
+#include "nvmxip.h"
+
+/* LBA Macros */
+
+#define DEFAULT_LBA_SHIFT 10 /* 1024 bytes per block */
+#define DEFAULT_LBA_COUNT 1024 /* block count */
+
+#define DEFAULT_LBA_SZ BIT(DEFAULT_LBA_SHIFT)
+
+/**
+ * nvmxip_post_bind() - post binding treatments
+ * @dev:	the NVMXIP device
+ *
+ * Create and probe a child block device.
+ *
+ * Return:
+ *
+ * 0 on success. Otherwise, failure
+ */
+static int nvmxip_post_bind(struct udevice *udev)
+{
+	int ret;
+	struct udevice *bdev = NULL;
+	char bdev_name[NVMXIP_BLKDEV_NAME_SZ + 1];
+	int devnum;
+
+	devnum = uclass_id_count(UCLASS_NVMXIP);
+	snprintf(bdev_name, NVMXIP_BLKDEV_NAME_SZ, "blk#%d", devnum);
+
+	ret = blk_create_devicef(udev, NVMXIP_BLKDRV_NAME, bdev_name, UCLASS_NVMXIP,
+				 devnum, DEFAULT_LBA_SZ,
+				 DEFAULT_LBA_COUNT, &bdev);
+	if (ret) {
+		log_err("[%s]: failure during creation of the block device %s, error %d\n",
+			udev->name, bdev_name, ret);
+		return ret;
+	}
+
+	ret = blk_probe_or_unbind(bdev);
+	if (ret) {
+		log_err("[%s]: failure during probing the block device %s, error %d\n",
+			udev->name, bdev_name, ret);
+		return ret;
+	}
+
+	log_info("[%s]: the block device %s ready for use\n", udev->name, bdev_name);
+
+	return 0;
+}
+
+UCLASS_DRIVER(nvmxip) = {
+	.name	   = "nvmxip",
+	.id	   = UCLASS_NVMXIP,
+	.post_bind = nvmxip_post_bind,
+};

drivers/mtd/nvmxip/nvmxip.c

@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
+ *
+ * Authors:
+ *   Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <log.h>
+#include <mapmem.h>
+#include <asm/io.h>
+#include <linux/bitops.h>
+#include <linux/errno.h>
+#include "nvmxip.h"
+
+/**
+ * nvmxip_mmio_rawread() - read from the XIP flash
+ * @address:	address of the data
+ * @value:	pointer to where storing the value read
+ *
+ * Read raw data from the XIP flash.
+ *
+ * Return:
+ *
+ * Always return 0.
+ */
+static int nvmxip_mmio_rawread(const phys_addr_t address, u64 *value)
+{
+	*value = readq(address);
+	return 0;
+}
+
+/**
+ * nvmxip_blk_read() - block device read operation
+ * @dev:	the block device
+ * @blknr:	first block number to read from
+ * @blkcnt:	number of blocks to read
+ * @buffer:	destination buffer
+ *
+ * Read data from the block storage device.
+ *
+ * Return:
+ *
+ * number of blocks read on success. Otherwise, failure
+ */
+static ulong nvmxip_blk_read(struct udevice *dev, lbaint_t blknr, lbaint_t blkcnt, void *buffer)
+{
+	struct nvmxip_plat *plat = dev_get_plat(dev->parent);
+	struct blk_desc *desc = dev_get_uclass_plat(dev);
+	/* number of the u64 words to read */
+	u32 qwords = (blkcnt * desc->blksz) / sizeof(u64);
+	/* physical address of the first block to read */
+	phys_addr_t blkaddr = plat->phys_base + blknr * desc->blksz;
+	u64 *virt_blkaddr;
+	u64 *pdst = buffer;
+	uint qdata_idx;
+
+	if (!pdst)
+		return -EINVAL;
+
+	log_debug("[%s]: reading from blknr: %lu , blkcnt: %lu\n", dev->name, blknr, blkcnt);
+
+	virt_blkaddr = map_sysmem(blkaddr, 0);
+
+	/* assumption: the data is virtually contiguous */
+
+	for (qdata_idx = 0 ; qdata_idx < qwords ; qdata_idx++)
+		nvmxip_mmio_rawread((phys_addr_t)(virt_blkaddr + qdata_idx), pdst++);
+
+	log_debug("[%s]:     src[0]: 0x%llx , dst[0]: 0x%llx , src[-1]: 0x%llx , dst[-1]: 0x%llx\n",
+		  dev->name,
+		  *virt_blkaddr,
+		  *(u64 *)buffer,
+		  *(u64 *)((u8 *)virt_blkaddr + desc->blksz * blkcnt - sizeof(u64)),
+		  *(u64 *)((u8 *)buffer + desc->blksz * blkcnt - sizeof(u64)));
+
+	unmap_sysmem(virt_blkaddr);
+
+	return blkcnt;
+}
+
+/**
+ * nvmxip_blk_probe() - block storage device probe
+ * @dev:	the block storage device
+ *
+ * Initialize the block storage descriptor.
+ *
+ * Return:
+ *
+ * Always return 0.
+ */
+static int nvmxip_blk_probe(struct udevice *dev)
+{
+	struct nvmxip_plat *plat = dev_get_plat(dev->parent);
+	struct blk_desc *desc = dev_get_uclass_plat(dev);
+
+	desc->lba = plat->lba;
+	desc->log2blksz = plat->lba_shift;
+	desc->blksz = BIT(plat->lba_shift);
+	desc->bdev = dev;
+
+	log_debug("[%s]: block storage layout\n    lbas: %lu , log2blksz: %d, blksz: %lu\n",
+		  dev->name, desc->lba, desc->log2blksz, desc->blksz);
+
+	return 0;
+}
+
+static const struct blk_ops nvmxip_blk_ops = {
+	.read	= nvmxip_blk_read,
+};
+
+U_BOOT_DRIVER(nvmxip_blk) = {
+	.name	= NVMXIP_BLKDRV_NAME,
+	.id	= UCLASS_BLK,
+	.probe	= nvmxip_blk_probe,
+	.ops	= &nvmxip_blk_ops,
+};

drivers/mtd/nvmxip/nvmxip.h

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright 2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
+ *
+ * Authors:
+ *   Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
+ */
+
+#ifndef __DRIVER_NVMXIP_H__
+#define __DRIVER_NVMXIP_H__
+
+#include <blk.h>
+
+#define NVMXIP_BLKDRV_NAME    "nvmxip-blk"
+#define NVMXIP_BLKDEV_NAME_SZ 20
+
+/**
+ * struct nvmxip_plat - the NVMXIP driver plat
+ *
+ * @phys_base:	NVM XIP device base address
+ * @lba_shift:	block size shift count
+ * @lba:	number of blocks
+ *
+ * The NVMXIP information read from the DT.
+ */
+struct nvmxip_plat {
+	phys_addr_t phys_base;
+	u32 lba_shift;
+	lbaint_t lba;
+};
+
+#endif /* __DRIVER_NVMXIP_H__ */

include/dm/uclass-id.h

@@ -89,6 +89,7 @@ enum uclass_id {
 	UCLASS_NOP,		/* No-op devices */
 	UCLASS_NORTHBRIDGE,	/* Intel Northbridge / SDRAM controller */
 	UCLASS_NVME,		/* NVM Express device */
+	UCLASS_NVMXIP,		/* NVM XIP devices */
 	UCLASS_P2SB,		/* (x86) Primary-to-Sideband Bus */
 	UCLASS_PANEL,		/* Display panel, such as an LCD */
 	UCLASS_PANEL_BACKLIGHT,	/* Backlight controller for panel */