bcm4908: backport mtd parser for Broadcom's U-Boot partition

Broadcom's U-Boot contains environment data blocks. They need to be
found (offsets aren't predefined) to access env variables.

Signed-off-by: Rafał Miłecki <[email protected]>

target/linux/bcm4908/config-5.10

@@ -133,6 +133,7 @@ CONFIG_MEMFD_CREATE=y
 CONFIG_MFD_SYSCON=y
 CONFIG_MIGRATION=y
 CONFIG_MODULES_USE_ELF_RELA=y
+CONFIG_MTD_BRCM_U_BOOT=y
 CONFIG_MTD_CMDLINE_PARTS=y
 CONFIG_MTD_NAND_BRCMNAND=y
 CONFIG_MTD_NAND_CORE=y

target/linux/bcm4908/patches-5.10/040-v6.1-mtd-parsers-add-Broadcom-s-U-Boot-parser.patch

@@ -0,0 +1,137 @@
+From 002181f5b150e60c77f21de7ad4dd10e4614cd91 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <[email protected]>
+Date: Mon, 11 Jul 2022 17:30:41 +0200
+Subject: [PATCH] mtd: parsers: add Broadcom's U-Boot parser
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Broadcom stores environment variables blocks inside U-Boot partition
+itself. This driver finds & registers them.
+
+Signed-off-by: Rafał Miłecki <[email protected]>
+Signed-off-by: Miquel Raynal <[email protected]>
+Link: https://lore.kernel.org/linux-mtd/[email protected]
+---
+ drivers/mtd/parsers/Kconfig       | 10 ++++
+ drivers/mtd/parsers/Makefile      |  1 +
+ drivers/mtd/parsers/brcm_u-boot.c | 84 +++++++++++++++++++++++++++++++
+ 3 files changed, 95 insertions(+)
+ create mode 100644 drivers/mtd/parsers/brcm_u-boot.c
+
+--- a/drivers/mtd/parsers/Kconfig
++++ b/drivers/mtd/parsers/Kconfig
+@@ -20,6 +20,16 @@ config MTD_BCM63XX_PARTS
+ 	  This provides partition parsing for BCM63xx devices with CFE
+ 	  bootloaders.
+ 
++config MTD_BRCM_U_BOOT
++	tristate "Broadcom's U-Boot partition parser"
++	depends on ARCH_BCM4908 || COMPILE_TEST
++	help
++	  Broadcom uses a custom way of storing U-Boot environment variables.
++	  They are placed inside U-Boot partition itself at unspecified offset.
++	  It's possible to locate them by looking for a custom header with a
++	  magic value. This driver does that and creates subpartitions for
++	  each found environment variables block.
++
+ config MTD_CMDLINE_PARTS
+ 	tristate "Command line partition table parsing"
+ 	depends on MTD
+--- a/drivers/mtd/parsers/Makefile
++++ b/drivers/mtd/parsers/Makefile
+@@ -2,6 +2,7 @@
+ obj-$(CONFIG_MTD_AR7_PARTS)		+= ar7part.o
+ obj-$(CONFIG_MTD_BCM47XX_PARTS)		+= bcm47xxpart.o
+ obj-$(CONFIG_MTD_BCM63XX_PARTS)		+= bcm63xxpart.o
++obj-$(CONFIG_MTD_BRCM_U_BOOT)		+= brcm_u-boot.o
+ obj-$(CONFIG_MTD_CMDLINE_PARTS)		+= cmdlinepart.o
+ obj-$(CONFIG_MTD_MYLOADER_PARTS)		+= myloader.o
+ obj-$(CONFIG_MTD_OF_PARTS)		+= ofpart.o
+--- /dev/null
++++ b/drivers/mtd/parsers/brcm_u-boot.c
+@@ -0,0 +1,84 @@
++// SPDX-License-Identifier: GPL-2.0-only
++/*
++ * Copyright © 2022 Rafał Miłecki <[email protected]>
++ */
++
++#include <linux/module.h>
++#include <linux/kernel.h>
++#include <linux/slab.h>
++#include <linux/mtd/mtd.h>
++#include <linux/mtd/partitions.h>
++
++#define BRCM_U_BOOT_MAX_OFFSET		0x200000
++#define BRCM_U_BOOT_STEP		0x1000
++
++#define BRCM_U_BOOT_MAX_PARTS		2
++
++#define BRCM_U_BOOT_MAGIC		0x75456e76	/* uEnv */
++
++struct brcm_u_boot_header {
++	__le32 magic;
++	__le32 length;
++} __packed;
++
++static const char *names[BRCM_U_BOOT_MAX_PARTS] = {
++	"u-boot-env",
++	"u-boot-env-backup",
++};
++
++static int brcm_u_boot_parse(struct mtd_info *mtd,
++			     const struct mtd_partition **pparts,
++			     struct mtd_part_parser_data *data)
++{
++	struct brcm_u_boot_header header;
++	struct mtd_partition *parts;
++	size_t bytes_read;
++	size_t offset;
++	int err;
++	int i = 0;
++
++	parts = kcalloc(BRCM_U_BOOT_MAX_PARTS, sizeof(*parts), GFP_KERNEL);
++	if (!parts)
++		return -ENOMEM;
++
++	for (offset = 0;
++	     offset < min_t(size_t, mtd->size, BRCM_U_BOOT_MAX_OFFSET);
++	     offset += BRCM_U_BOOT_STEP) {
++		err = mtd_read(mtd, offset, sizeof(header), &bytes_read, (uint8_t *)&header);
++		if (err && !mtd_is_bitflip(err)) {
++			pr_err("Failed to read from %s at 0x%zx: %d\n", mtd->name, offset, err);
++			continue;
++		}
++
++		if (le32_to_cpu(header.magic) != BRCM_U_BOOT_MAGIC)
++			continue;
++
++		parts[i].name = names[i];
++		parts[i].offset = offset;
++		parts[i].size = sizeof(header) + le32_to_cpu(header.length);
++		i++;
++		pr_info("offset:0x%zx magic:0x%08x BINGO\n", offset, header.magic);
++
++		if (i == BRCM_U_BOOT_MAX_PARTS)
++			break;
++	}
++
++	*pparts = parts;
++
++	return i;
++};
++
++static const struct of_device_id brcm_u_boot_of_match_table[] = {
++	{ .compatible = "brcm,u-boot" },
++	{},
++};
++MODULE_DEVICE_TABLE(of, brcm_u_boot_of_match_table);
++
++static struct mtd_part_parser brcm_u_boot_mtd_parser = {
++	.parse_fn = brcm_u_boot_parse,
++	.name = "brcm_u-boot",
++	.of_match_table = brcm_u_boot_of_match_table,
++};
++module_mtd_part_parser(brcm_u_boot_mtd_parser);
++
++MODULE_LICENSE("GPL");