[PATCH v2 1/3] fdt: validate/fix cells count on mtdpart fixup

[Francesco Dolcini <francesco@dolcini.it>]

From: Francesco Dolcini <francesco.dolcini@toradex.com>

Fixup #size-cells value when updating the MTD partitions, this is
required to prevent issues in case the MTD parent set #size-cells to
zero.
This could happen for example in the legacy case in which the partitions
are created as direct child of the mtd node and that specific node has
no children. Recent clean-up on Linux device tree files created a boot
regression on colibri-imx7 [0].

This fixup has the limitation to assume 32-bit (#size-cells=1)
addressing, therefore it will not work with device bigger than 4GiB.

This change also enforce #address-cells to be the same as #size-cells,
this was already silently enforced by fdt_node_set_part_info(), now this
is checked explicitly and partition fixup will just fail in such case.

When the partition list is static the preferred way to pass the mtd
partition list to the kernel is to either define those in the source DTS
file or use mtdparts= in the command line.
Tweaking the DT from U-Boot should be avoided, unless some dynamic
changes are required, since it proved to be problematic when not
following the evolution of the "standard".

Link: https://lore.kernel.org/all/Y4dgBTGNWpM6SQXI@francesco-nb.int.toradex.com/
Link: https://lore.kernel.org/all/20221202071900.1143950-1-francesco@dolcini.it/
Cc: Marek Vasut <marex@denx.de>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
---
v2: improved commit message
---
 common/fdt_support.c | 45 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/common/fdt_support.c b/common/fdt_support.c
index dbceec6f2dcc..3aee826e60cf 100644
--- a/common/fdt_support.c
+++ b/common/fdt_support.c
@@ -877,27 +877,20 @@ static int fdt_del_partitions(void *blob, int parent_offset)
 	return 0;
 }
 
-static int fdt_node_set_part_info(void *blob, int parent_offset,
+/* This expects #address-cells and #size-cells to have same value */
+static int fdt_node_set_part_info(void *blob, int parent_offset, int sizecell,
 				  struct mtd_device *dev)
 {
 	struct list_head *pentry;
 	struct part_info *part;
 	int off, ndepth = 0;
 	int part_num, ret;
-	int sizecell;
 	char buf[64];
 
 	ret = fdt_del_partitions(blob, parent_offset);
 	if (ret < 0)
 		return ret;
 
-	/*
-	 * Check if size/address is 1 or 2 cells.
-	 * We assume #address-cells and #size-cells have same value.
-	 */
-	sizecell = fdt_getprop_u32_default_node(blob, parent_offset,
-						0, "#size-cells", 1);
-
 	/*
 	 * Check if it is nand {}; subnode, adjust
 	 * the offset in this case
@@ -992,6 +985,31 @@ err_prop:
 	return ret;
 }
 
+static int fdt_mtdparts_cell_cnt(void *fdt, int off)
+{
+	int sizecell, addrcell;
+
+	sizecell = fdt_getprop_u32_default_node(fdt, off, 0, "#size-cells", 0);
+	if (sizecell != 1 && sizecell != 2) {
+		printf("%s: Invalid or missing #size-cells %d value, assuming 1\n",
+		       __func__, sizecell);
+
+		sizecell = 1;
+		if (fdt_setprop_u32(fdt, off, "#size-cells", sizecell))
+			return -1;
+	}
+
+	addrcell = fdt_getprop_u32_default_node(fdt, off, 0,
+						"#address-cells", 0);
+	if (addrcell != sizecell) {
+		printf("%s: Invalid #address-cells %d != #size-cells %d, aborting\n",
+		       __func__, addrcell, sizecell);
+		return -1;
+	}
+
+	return sizecell;
+}
+
 /*
  * Update partitions in nor/nand nodes using info from
  * mtdparts environment variable. The nodes to update are
@@ -1037,12 +1055,19 @@ void fdt_fixup_mtdparts(void *blob, const struct node_info *node_info,
 
 			dev = device_find(node_info[i].type, idx++);
 			if (dev) {
+				int cell;
+
 				parts = fdt_subnode_offset(blob, noff,
 							   "partitions");
 				if (parts < 0)
 					parts = noff;
 
-				if (fdt_node_set_part_info(blob, parts, dev))
+				cell = fdt_mtdparts_cell_cnt(blob, parts);
+				if (cell < 0)
+					return;
+
+				if (fdt_node_set_part_info(blob, parts,
+							   cell, dev))
 					return; /* return on error */
 			}
 		}
-- 
2.25.1


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