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Commit fc28c39f authored by Wolfram Sang's avatar Wolfram Sang Committed by David Woodhouse
Browse files

mtd: maps: add mtd-ram support to physmap_of 



Use physmap_of to access RAMs as mtd and add documenation for it. This approach
is a lot less intrusive as adding an of-wrapper around plat-ram.c. As most
extensions of plat-ram.c (e.g. custom map-functions) can't be mapped to the
device tree anyhow, extending physmap_of seems to be the cleanest approach.

Tested with a phyCORE-MPC5121e.

Signed-off-by: default avatarWolfram Sang <w.sang@pengutronix.de>
Cc: Vitaly Wool <vwool@ru.mvista.com>
Cc: Artem Bityutskiy <dedekind@infradead.org>
Cc: Ken MacLeod <ken@bitsko.slc.ut.us>
Cc: Albrecht Dreß <albrecht.dress@arcor.de>
Acked-by: default avatarGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent 223cf6c3

Documentation/powerpc/dts-bindings/mtd-physmap.txt

+26 −16
Original line number Diff line number Diff line 
CFI or JEDEC memory-mapped NOR flash

CFI or JEDEC memory-mapped NOR flash, MTD-RAM (NVRAM...)



Flash chips (Memory Technology Devices) are often used for solid state

file systems on embedded devices.



 - compatible : should contain the specific model of flash chip(s)

   used, if known, followed by either "cfi-flash" or "jedec-flash"

 - reg : Address range(s) of the flash chip(s)

 - compatible : should contain the specific model of mtd chip(s)

   used, if known, followed by either "cfi-flash", "jedec-flash"

   or "mtd-ram".

 - reg : Address range(s) of the mtd chip(s)

   It's possible to (optionally) define multiple "reg" tuples so that

   non-identical NOR chips can be described in one flash node.

 - bank-width : Width (in bytes) of the flash bank.  Equal to the

   non-identical chips can be described in one node.

 - bank-width : Width (in bytes) of the bank.  Equal to the

   device width times the number of interleaved chips.

 - device-width : (optional) Width of a single flash chip.  If

 - device-width : (optional) Width of a single mtd chip.  If

   omitted, assumed to be equal to 'bank-width'.

 - #address-cells, #size-cells : Must be present if the flash has

 - #address-cells, #size-cells : Must be present if the device has

   sub-nodes representing partitions (see below).  In this case

   both #address-cells and #size-cells must be equal to 1.
@@ -22,24 +23,24 @@ are defined: 
 - vendor-id : Contains the flash chip's vendor id (1 byte).

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



In addition to the information on the flash bank itself, the

In addition to the information on the mtd bank itself, the

device tree may optionally contain additional information

describing partitions of the flash address space.  This can be

describing partitions of the address space.  This can be

used on platforms which have strong conventions about which

portions of the flash are used for what purposes, but which don't

portions of a flash are used for what purposes, but which don't

use an on-flash partition table such as RedBoot.



Each partition is represented as a sub-node of the flash device.

Each partition is represented as a sub-node of the mtd device.

Each node's name represents the name of the corresponding

partition of the flash device.

partition of the mtd device.



Flash partitions

 - reg : The partition's offset and size within the flash bank.

 - label : (optional) The label / name for this flash partition.

 - reg : The partition's offset and size within the mtd bank.

 - label : (optional) The label / name for this partition.

   If omitted, the label is taken from the node name (excluding

   the unit address).

 - read-only : (optional) This parameter, if present, is a hint to

   Linux that this flash partition should only be mounted

   Linux that this partition should only be mounted

   read-only.  This is usually used for flash partitions

   containing early-boot firmware images or data which should not

   be clobbered.
@@ -78,3 +79,12 @@ Here an example with multiple "reg" tuples: 
			reg = <0 0x04000000>;

		};

	};



An example using SRAM:



	sram@2,0 {

		compatible = "samsung,k6f1616u6a", "mtd-ram";

		reg = <2 0 0x00200000>;

		bank-width = <2>;

	};

drivers/mtd/maps/physmap_of.c

+4 −0
Original line number Diff line number Diff line
@@ -361,6 +361,10 @@ static struct of_device_id of_flash_match[] = { 
		.compatible	= "jedec-flash",

		.data		= (void *)"jedec_probe",

	},

	{

		.compatible     = "mtd-ram",

		.data           = (void *)"map_ram",

	},

	{

		.type		= "rom",

		.compatible	= "direct-mapped"