mtd: rawnand: add an option to specify NAND chip as a boot device

Allow to define a NAND chip as a boot device. This can be helpful
for the selection of the ECC algorithm and strength in case the boot
ROM supports only a subset of controller provided options.
Signed-off-by: NStefan Agner <stefan@agner.ch>
Reviewed-by: NBoris Brezillon <boris.brezillon@bootlin.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>

Documentation/devicetree/bindings/mtd/nand.txt

@@ -43,6 +43,10 @@ Optional NAND chip properties:
 		     This is particularly useful when only the in-band area is
 		     used by the upper layers, and you want to make your NAND
 		     as reliable as possible.
+- nand-is-boot-medium: Whether the NAND chip is a boot medium. Drivers might use
+		       this information to select ECC algorithms supported by
+		       the boot ROM or similar restrictions.
+
 - nand-rb: shall contain the native Ready/Busy ids.
 
 The ECC strength and ECC step size properties define the correction capability

drivers/mtd/nand/raw/nand_base.c

@@ -5859,6 +5859,9 @@ static int nand_dt_init(struct nand_chip *chip)
 	if (of_get_nand_bus_width(dn) == 16)
 		chip->options |= NAND_BUSWIDTH_16;
 
+	if (of_property_read_bool(dn, "nand-is-boot-medium"))
+		chip->options |= NAND_IS_BOOT_MEDIUM;
+
 	if (of_get_nand_on_flash_bbt(dn))
 		chip->bbt_options |= NAND_BBT_USE_FLASH;
 

include/linux/mtd/rawnand.h

@@ -219,6 +219,12 @@ enum nand_ecc_algo {
  */
 #define NAND_WAIT_TCCS		0x00200000
 
+/*
+ * Whether the NAND chip is a boot medium. Drivers might use this information
+ * to select ECC algorithms supported by the boot ROM or similar restrictions.
+ */
+#define NAND_IS_BOOT_MEDIUM	0x00400000
+
 /* Options set by nand scan */
 /* Nand scan has allocated controller struct */
 #define NAND_CONTROLLER_ALLOC	0x80000000