Commit 6958024a authored by Aaron Sierra's avatar Aaron Sierra Committed by Brian Norris
Browse files

mtd: map_rom: Support UBI on ROM 



UBI needs to know the physical erase block size, even on read-only
devices, since it defines the on-device layout. Use a device-tree
provided value to support previously written UBI on read-only NOR.

UBI also needs a non-zero writebufsize, so we set it to one.

Note: This was implemented because hardware write-protected CFI
      NOR cannot be probed for the physical erase block size.

Signed-off-by: default avatarJoe Schultz <jschultz@xes-inc.ccom>
Signed-off-by: default avatarAaron Sierra <asierra@xes-inc.ccom>
[Brian: removed unneeded #ifdef, note 'optional' erase-size property]
Signed-off-by: default avatarBrian Norris <computersforpeace@gmail.com>
parent 3fc1cf5f

Documentation/devicetree/bindings/mtd/mtd-physmap.txt

+5 −0
Original line number Diff line number Diff line
@@ -36,6 +36,11 @@ are defined: 
 - vendor-id : Contains the flash chip's vendor id (1 byte).

 - device-id : Contains the flash chip's device id (1 byte).



For ROM compatible devices (and ROM fallback from cfi-flash), the following

additional (optional) property is defined:



 - erase-size : The chip's physical erase block size in bytes.



The device tree may optionally contain sub-nodes describing partitions of the

address space. See partition.txt for more detail.

drivers/mtd/chips/map_rom.c

+12 −1
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/errno.h>

#include <linux/slab.h>

#include <linux/init.h>

#include <linux/of.h>

#include <linux/mtd/mtd.h>

#include <linux/mtd/map.h>
@@ -28,6 +29,15 @@ static struct mtd_chip_driver maprom_chipdrv = { 
	.module	= THIS_MODULE

};



static unsigned int default_erasesize(struct map_info *map)

{

	const __be32 *erase_size = NULL;



	erase_size = of_get_property(map->device_node, "erase-size", NULL);



	return !erase_size ? map->size : be32_to_cpu(*erase_size);

}



static struct mtd_info *map_rom_probe(struct map_info *map)

{

	struct mtd_info *mtd;
@@ -47,8 +57,9 @@ static struct mtd_info *map_rom_probe(struct map_info *map) 
	mtd->_sync = maprom_nop;

	mtd->_erase = maprom_erase;

	mtd->flags = MTD_CAP_ROM;

	mtd->erasesize = map->size;

	mtd->erasesize = default_erasesize(map);

	mtd->writesize = 1;

	mtd->writebufsize = 1;



	__module_get(THIS_MODULE);

	return mtd;

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