mtd: parsers: ofpart: support BCM4908 fixed partitions

Some devices use fixed partitioning with some partitions requiring some
extra logic. E.g. BCM4908 may have multiple firmware partitions but
detecting currently used one requires checking bootloader parameters.

To support such cases without duplicating a lot of code (without copying
most of the ofpart.c code) support for post-parsing callback was added.

BCM4908 support in ofpart can be enabled using config option and results
in compiling & executing a specific callback. It simply reads offset of
currently used firmware partition from the DT. Bootloader specifies it
using the "brcm_blparms" property.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210301105823.31032-1-zajec5@gmail.com

drivers/mtd/parsers/Kconfig

@@ -67,6 +67,15 @@ config MTD_OF_PARTS
 	  flash memory node, as described in
 	  Documentation/devicetree/bindings/mtd/partition.txt.
 
+config MTD_OF_PARTS_BCM4908
+	bool "BCM4908 partitioning support"
+	depends on MTD_OF_PARTS && (ARCH_BCM4908 || COMPILE_TEST)
+	default ARCH_BCM4908
+	help
+	  This provides partitions parser for BCM4908 family devices
+	  that can have multiple "firmware" partitions. It takes care of
+	  finding currently used one and backup ones.
+
 config MTD_PARSER_IMAGETAG
 	tristate "Parser for BCM963XX Image Tag format partitions"
 	depends on BCM63XX || BMIPS_GENERIC || COMPILE_TEST

drivers/mtd/parsers/Makefile

@@ -4,6 +4,8 @@ obj-$(CONFIG_MTD_BCM47XX_PARTS)		+= bcm47xxpart.o
 obj-$(CONFIG_MTD_BCM63XX_PARTS)		+= bcm63xxpart.o
 obj-$(CONFIG_MTD_CMDLINE_PARTS)		+= cmdlinepart.o
 obj-$(CONFIG_MTD_OF_PARTS)		+= ofpart.o
+ofpart-y				+= ofpart_core.o
+ofpart-$(CONFIG_MTD_OF_PARTS_BCM4908)	+= ofpart_bcm4908.o
 obj-$(CONFIG_MTD_PARSER_IMAGETAG)	+= parser_imagetag.o
 obj-$(CONFIG_MTD_AFS_PARTS)		+= afs.o
 obj-$(CONFIG_MTD_PARSER_TRX)		+= parser_trx.o

drivers/mtd/parsers/ofpart_bcm4908.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Rafał Miłecki <rafal@milecki.pl>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/mtd/mtd.h>
+#include <linux/slab.h>
+#include <linux/mtd/partitions.h>
+
+#include "ofpart_bcm4908.h"
+
+#define BLPARAMS_FW_OFFSET		"NAND_RFS_OFS"
+
+static long long bcm4908_partitions_fw_offset(void)
+{
+	struct device_node *root;
+	struct property *prop;
+	const char *s;
+
+	root = of_find_node_by_path("/");
+	if (!root)
+		return -ENOENT;
+
+	of_property_for_each_string(root, "brcm_blparms", prop, s) {
+		size_t len = strlen(BLPARAMS_FW_OFFSET);
+		unsigned long offset;
+		int err;
+
+		if (strncmp(s, BLPARAMS_FW_OFFSET, len) || s[len] != '=')
+			continue;
+
+		err = kstrtoul(s + len + 1, 0, &offset);
+		if (err) {
+			pr_err("failed to parse %s\n", s + len + 1);
+			return err;
+		}
+
+		return offset << 10;
+	}
+
+	return -ENOENT;
+}
+
+int bcm4908_partitions_post_parse(struct mtd_info *mtd, struct mtd_partition *parts, int nr_parts)
+{
+	long long fw_offset;
+	int i;
+
+	fw_offset = bcm4908_partitions_fw_offset();
+
+	for (i = 0; i < nr_parts; i++) {
+		if (of_device_is_compatible(parts[i].of_node, "brcm,bcm4908-firmware")) {
+			if (fw_offset < 0 || parts[i].offset == fw_offset)
+				parts[i].name = "firmware";
+			else
+				parts[i].name = "backup";
+		}
+	}
+
+	return 0;
+}

drivers/mtd/parsers/ofpart_bcm4908.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __BCM4908_PARTITIONS_H
+#define __BCM4908_PARTITIONS_H
+
+#ifdef CONFIG_MTD_OF_PARTS_BCM4908
+int bcm4908_partitions_post_parse(struct mtd_info *mtd, struct mtd_partition *parts, int nr_parts);
+#else
+static inline int bcm4908_partitions_post_parse(struct mtd_info *mtd, struct mtd_partition *parts,
+						int nr_parts)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
+#endif

drivers/mtd/parsers/ofpart.c → drivers/mtd/parsers/ofpart_core.c

@@ -16,6 +16,18 @@
 #include <linux/slab.h>
 #include <linux/mtd/partitions.h>
 
+#include "ofpart_bcm4908.h"
+
+struct fixed_partitions_quirks {
+	int (*post_parse)(struct mtd_info *mtd, struct mtd_partition *parts, int nr_parts);
+};
+
+struct fixed_partitions_quirks bcm4908_partitions_quirks = {
+	.post_parse = bcm4908_partitions_post_parse,
+};
+
+static const struct of_device_id parse_ofpart_match_table[];
+
 static bool node_has_compatible(struct device_node *pp)
 {
 	return of_get_property(pp, "compatible", NULL);
@@ -25,6 +37,8 @@ static int parse_fixed_partitions(struct mtd_info *master,
 				  const struct mtd_partition **pparts,
 				  struct mtd_part_parser_data *data)
 {
+	const struct fixed_partitions_quirks *quirks;
+	const struct of_device_id *of_id;
 	struct mtd_partition *parts;
 	struct device_node *mtd_node;
 	struct device_node *ofpart_node;
@@ -33,7 +47,6 @@ static int parse_fixed_partitions(struct mtd_info *master,
 	int nr_parts, i, ret = 0;
 	bool dedicated = true;
 
-
 	/* Pull of_node from the master device node */
 	mtd_node = mtd_get_of_node(master);
 	if (!mtd_node)
@@ -50,11 +63,16 @@ static int parse_fixed_partitions(struct mtd_info *master,
 			 master->name, mtd_node);
 		ofpart_node = mtd_node;
 		dedicated = false;
-	} else if (!of_device_is_compatible(ofpart_node, "fixed-partitions")) {
+	}
+
+	of_id = of_match_node(parse_ofpart_match_table, ofpart_node);
+	if (dedicated && !of_id) {
 		/* The 'partitions' subnode might be used by another parser */
 		return 0;
 	}
 
+	quirks = of_id ? of_id->data : NULL;
+
 	/* First count the subnodes */
 	nr_parts = 0;
 	for_each_child_of_node(ofpart_node,  pp) {
@@ -126,6 +144,9 @@ static int parse_fixed_partitions(struct mtd_info *master,
 	if (!nr_parts)
 		goto ofpart_none;
 
+	if (quirks && quirks->post_parse)
+		quirks->post_parse(master, parts, nr_parts);
+
 	*pparts = parts;
 	return nr_parts;
 
@@ -140,7 +161,10 @@ static int parse_fixed_partitions(struct mtd_info *master,
 }
 
 static const struct of_device_id parse_ofpart_match_table[] = {
+	/* Generic */
 	{ .compatible = "fixed-partitions" },
+	/* Customized */
+	{ .compatible = "brcm,bcm4908-partitions", .data = &bcm4908_partitions_quirks, },
 	{},
 };
 MODULE_DEVICE_TABLE(of, parse_ofpart_match_table);