linux/Documentation/devicetree/bindings/mtd/atmel-nand.txt
Josh Wu 6054d4d563 mtd: atmel_nand: enable Nand Flash Controller (NFC) write via sram
This patch enable writing nand flash via NFC SRAM. It will minimize the CPU
overhead. The SRAM write only support ECC_NONE and ECC_HW with PMECC.

To enable this NFC write by SRAM feature, you can add a string in dts under
NFC driver node.

This driver has been tested on SAMA5D3X-EK with JFFS2, YAFFS2, UBIFS and
mtd-utils.

Here is part of mtd_speedtest (writing test) result, compare with non-NFC
writing, it reduces %65 cpu load with loss %12 speed.

- commands use to test:
  # insmod /mnt/mtd_speedtest.ko dev=2 &
  # top -n 30 -d 1 | grep speedtest

- test result:
=================================================
mtd_speedtest: MTD device: 2
mtd_speedtest: MTD device size 41943040, eraseblock size 131072, page size 2048, count of eraseblocks 320, pages per eraseblock 64, OOB size 64
mtd_speedtest: testing eraseblock write speed
  509   495 root     D     1164   0%   7% insmod /mnt/mtd_speedtest.ko dev=2
  509   495 root     D     1164   0%   8% insmod /mnt/mtd_speedtest.ko dev=2
  509   495 root     R     1164   0%   5% insmod /mnt/mtd_speedtest.ko dev=2
mtd_speedtest: eraseblock write speed is 5194 KiB/s
mtd_speedtest: testing page write speed
  509   495 root     D     1164   0%  32% insmod /mnt/mtd_speedtest.ko dev=2
  509   495 root     D     1164   0%  27% insmod /mnt/mtd_speedtest.ko dev=2
  509   495 root     D     1164   0%  25% insmod /mnt/mtd_speedtest.ko dev=2
  509   495 root     D     1164   0%  30% insmod /mnt/mtd_speedtest.ko dev=2
mtd_speedtest: page write speed is 5024 KiB/s

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2013-08-05 21:07:51 +01:00

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Atmel NAND flash
Required properties:
- compatible : "atmel,at91rm9200-nand".
- reg : should specify localbus address and size used for the chip,
and hardware ECC controller if available.
If the hardware ECC is PMECC, it should contain address and size for
PMECC, PMECC Error Location controller and ROM which has lookup tables.
- atmel,nand-addr-offset : offset for the address latch.
- atmel,nand-cmd-offset : offset for the command latch.
- #address-cells, #size-cells : Must be present if the device has sub-nodes
representing partitions.
- gpios : specifies the gpio pins to control the NAND device. detect is an
optional gpio and may be set to 0 if not present.
Optional properties:
- atmel,nand-has-dma : boolean to support dma transfer for nand read/write.
- nand-ecc-mode : String, operation mode of the NAND ecc mode, soft by default.
Supported values are: "none", "soft", "hw", "hw_syndrome", "hw_oob_first",
"soft_bch".
- atmel,has-pmecc : boolean to enable Programmable Multibit ECC hardware.
Only supported by at91sam9x5 or later sam9 product.
- atmel,pmecc-cap : error correct capability for Programmable Multibit ECC
Controller. Supported values are: 2, 4, 8, 12, 24.
- atmel,pmecc-sector-size : sector size for ECC computation. Supported values
are: 512, 1024.
- atmel,pmecc-lookup-table-offset : includes two offsets of lookup table in ROM
for different sector size. First one is for sector size 512, the next is for
sector size 1024.
- nand-bus-width : 8 or 16 bus width if not present 8
- nand-on-flash-bbt: boolean to enable on flash bbt option if not present false
- Nand Flash Controller(NFC) is a slave driver under Atmel nand flash
- Required properties:
- compatible : "atmel,sama5d3-nfc".
- reg : should specify the address and size used for NFC command registers,
NFC registers and NFC Sram. NFC Sram address and size can be absent
if don't want to use it.
- Optional properties:
- atmel,write-by-sram: boolean to enable NFC write by sram.
Examples:
nand0: nand@40000000,0 {
compatible = "atmel,at91rm9200-nand";
#address-cells = <1>;
#size-cells = <1>;
reg = <0x40000000 0x10000000
0xffffe800 0x200
>;
atmel,nand-addr-offset = <21>; /* ale */
atmel,nand-cmd-offset = <22>; /* cle */
nand-on-flash-bbt;
nand-ecc-mode = "soft";
gpios = <&pioC 13 0 /* rdy */
&pioC 14 0 /* nce */
0 /* cd */
>;
partition@0 {
...
};
};
/* for PMECC supported chips */
nand0: nand@40000000 {
compatible = "atmel,at91rm9200-nand";
#address-cells = <1>;
#size-cells = <1>;
reg = < 0x40000000 0x10000000 /* bus addr & size */
0xffffe000 0x00000600 /* PMECC addr & size */
0xffffe600 0x00000200 /* PMECC ERRLOC addr & size */
0x00100000 0x00100000 /* ROM addr & size */
>;
atmel,nand-addr-offset = <21>; /* ale */
atmel,nand-cmd-offset = <22>; /* cle */
nand-on-flash-bbt;
nand-ecc-mode = "hw";
atmel,has-pmecc; /* enable PMECC */
atmel,pmecc-cap = <2>;
atmel,pmecc-sector-size = <512>;
atmel,pmecc-lookup-table-offset = <0x8000 0x10000>;
gpios = <&pioD 5 0 /* rdy */
&pioD 4 0 /* nce */
0 /* cd */
>;
partition@0 {
...
};
};
/* for NFC supported chips */
nand0: nand@40000000 {
compatible = "atmel,at91rm9200-nand";
#address-cells = <1>;
#size-cells = <1>;
ranges;
...
nfc@70000000 {
compatible = "atmel,sama5d3-nfc";
#address-cells = <1>;
#size-cells = <1>;
reg = <
0x70000000 0x10000000 /* NFC Command Registers */
0xffffc000 0x00000070 /* NFC HSMC regs */
0x00200000 0x00100000 /* NFC SRAM banks */
>;
};
};