154 lines
6.6 KiB
Plaintext
154 lines
6.6 KiB
Plaintext
|
STLinux NAND AFM driver - Release Notes
|
||
|
|
|
||
|
|
1. Overview
|
||
|
|
|
||
|
|
The stm-nand-afm driver adds support for the ST Microelectronics NAND AFM
|
||
|
|
Controller. The AFM Controller offers H/W assisted ECC, automated command
|
||
|
|
sequences, and a 128-byte data FIFO, all of which contribute to an improved
|
||
|
|
performance over the existing stm-nand-emi and stm-nand-flex drivers.
|
||
|
|
|
||
|
|
However, the AFM controller uses a different ECC layout to the default linux S/W
|
||
|
|
ECC layout (as used by the stm-nand-emi and stm-nand-flex drivers). Furthermore,
|
||
|
|
the AFM4 ECC layout may clash with the location of the factory-programmed
|
||
|
|
bad-block markers. As a result, a number of issues must be considered before
|
||
|
|
enabling the stm-nand-afm driver, particularly when migrating from the
|
||
|
|
stm-nand-flex or stm-nand-emi drivers.
|
||
|
|
|
||
|
|
2. ECC Schemes
|
||
|
|
|
||
|
|
The user needs to be aware of 3 ECC schemes:
|
||
|
|
|
||
|
|
* 3/256 ECC: 3 bytes of ECC per 256 bytes of data. This is the default linux
|
||
|
|
S/W ECC scheme and is used by the stm-nand-emi and stm-nand-flex drivers.
|
||
|
|
|
||
|
|
* boot-mode ECC: 3 bytes of ECC per 128 bytes of data (with an additional 1-byte
|
||
|
|
ID marker). This format is used by the NAND boot-controller. The layout of
|
||
|
|
the ECC bytes in OOB is such that it may clash with the location of
|
||
|
|
factory-programmed bad-block markers. Therefore, the use of FLASH-resident
|
||
|
|
bad block tables (BBTs) is advised to keep track of bad-blocks. Ideally, the
|
||
|
|
BBTs should be written to the device prior to writing any boot-mode data.
|
||
|
|
However, STLinux does now recognise boot-mode ECC data when scanning for
|
||
|
|
bad-blocks, so the creation of the FLASH-resident BBTs can be deferred to the
|
||
|
|
first boot if preferred, or avoided all-together. (Previously, STLinux would
|
||
|
|
typically interpret boot-mode ECC data as bad-block markers, and therefore
|
||
|
|
writing BBTs to FLASH prior to writing boot-mode data was mandatory.)
|
||
|
|
|
||
|
|
* AFM4 ECC: 4 bytes of ECC per 512 bytes of data (with an additional 3-byte ID
|
||
|
|
marker). This format is used by the stm-nand-afm driver (and is the only
|
||
|
|
scheme recognised by the PBL (Primary Boot Loader)). As with boot-mode ECC,
|
||
|
|
the layout in OOB is such that it may clash with the location of
|
||
|
|
factory-programmed bad-block markers. The same advice as before applies: the
|
||
|
|
use of FLASH-resident BBTs is recommended, although STLinux will recognise
|
||
|
|
correctly AFM4 data if required to perform the bad-block scan itself.
|
||
|
|
|
||
|
|
|
||
|
|
3. Migrating from stm-nand-flex or stm-nand-emi drivers
|
||
|
|
|
||
|
|
If the NAND device has been used previously with the stm-nand-emi or
|
||
|
|
stm-nand-flex driver, then it will need to be wiped before enabling the
|
||
|
|
stm-nand-afm driver. This includes erasing data blocks and any FLASH-resident
|
||
|
|
BBTs that may be present. However, care must be taken not to erase any
|
||
|
|
factory-programed bad-block markers since it may not be possible to recover this
|
||
|
|
information from the NAND device if the block is erased.
|
||
|
|
|
||
|
|
3.1 Erasing data blocks
|
||
|
|
|
||
|
|
This can be achieved using the flash_eraseall command on the NAND device's MTD
|
||
|
|
partitions. flash_eraseall is safe to use here since it will not attempt to
|
||
|
|
erase any blocks that are marked bad (this is true even if the debugfs attribute
|
||
|
|
"nanderasebb" has been set).
|
||
|
|
|
||
|
|
For example:
|
||
|
|
|
||
|
|
root@jim:~# cat /proc/mtd
|
||
|
|
dev: size erasesize name
|
||
|
|
mtd0: 00400000 00020000 "My NOR Root"
|
||
|
|
mtd1: 07c00000 00020000 "My NOR Home"
|
||
|
|
mtd2: 00800000 00020000 "NAND root"
|
||
|
|
mtd3: 3f800000 00020000 "NAND home"
|
||
|
|
root@jim:~# flash_eraseall /dev/mtd2
|
||
|
|
|
||
|
|
Skipping bad block at 0x00000000
|
||
|
|
|
||
|
|
Skipping bad block at 0x00020000
|
||
|
|
Erasing 128 Kibyte @ 40000 -- 3 % complete.
|
||
|
|
Skipping bad block at 0x00060000
|
||
|
|
Erasing 128 Kibyte @ a0000 -- 7 % complete.
|
||
|
|
Skipping bad block at 0x000c0000
|
||
|
|
Erasing 128 Kibyte @ 7e0000 -- 98 % complete.
|
||
|
|
root@jim:~# flash_eraseall /dev/mtd2
|
||
|
|
|
||
|
|
Skipping bad block at 0x00000000
|
||
|
|
|
||
|
|
Skipping bad block at 0x00020000
|
||
|
|
Erasing 128 Kibyte @ 40000 -- 3 % complete.
|
||
|
|
Skipping bad block at 0x00060000
|
||
|
|
Erasing 128 Kibyte @ a0000 -- 7 % complete.
|
||
|
|
Skipping bad block at 0x000c0000
|
||
|
|
Erasing 128 Kibyte @ 7e0000 -- 98 % complete.
|
||
|
|
root@jim:~# flash_eraseall /dev/mtd3
|
||
|
|
Erasing 128 Kibyte @ 115c0000 -- 27 % complete.
|
||
|
|
Skipping bad block at 0x115e0000
|
||
|
|
Erasing 128 Kibyte @ 2e140000 -- 72 % complete.
|
||
|
|
Skipping bad block at 0x2e160000
|
||
|
|
Erasing 128 Kibyte @ 36380000 -- 85 % complete.
|
||
|
|
Skipping bad block at 0x363a0000
|
||
|
|
Erasing 128 Kibyte @ 3f7e0000 -- 99 % complete.
|
||
|
|
|
||
|
|
|
||
|
|
3.2 Erasing FLASH-resident BBTs
|
||
|
|
|
||
|
|
If FLASH-resident BBTs have been used in the past, then these will need to be
|
||
|
|
erased manually. linux protects the area reserved for FLASH-resident BBTs
|
||
|
|
(typically the last 4 blocks of the NAND device) by presenting them as
|
||
|
|
bad-blocks to user applications. In order to erase the BBTs:
|
||
|
|
|
||
|
|
1) Enable the erasing of blocks that are marked as bad, via the debugfs
|
||
|
|
attribute "nanderasebb" (requires CONFIG_DEBUG_FS):
|
||
|
|
|
||
|
|
root@jim:~# echo 1 > /debug/nanderasebb
|
||
|
|
|
||
|
|
2) Use flash_erase on the blocks reserved for BBTs. For example:
|
||
|
|
|
||
|
|
root@jim:~# cat /proc/mtd
|
||
|
|
dev: size erasesize name
|
||
|
|
mtd0: 00400000 00020000 "My NOR Root"
|
||
|
|
mtd1: 07c00000 00020000 "My NOR Home"
|
||
|
|
mtd2: 00800000 00020000 "NAND root"
|
||
|
|
mtd3: 3f800000 00020000 "NAND home"
|
||
|
|
root@jim:~# flash_erase /dev/mtd3 0x3f780000 4
|
||
|
|
Erase Total 4 Units
|
||
|
|
Performing Flash Erase of length 131072 at offset 0x3f7e0000 done
|
||
|
|
|
||
|
|
|
||
|
|
4 Configuring the stm-nand-afm driver
|
||
|
|
|
||
|
|
4.1 Board setup file
|
||
|
|
|
||
|
|
The board setup file uses a marco, STM_NAND_DEVICE, to fill-in the NAND platform
|
||
|
|
data. The first argument is the driver binding which should be changed to
|
||
|
|
"stm-nand-afm". It is also recommended to add "NAND_USE_FLASH_BBT" to the chip
|
||
|
|
options bit-field (the last argument), if not already present.
|
||
|
|
|
||
|
|
4.2 Kconfig options
|
||
|
|
|
||
|
|
* MTD_NAND_STM_AFM: Enable the stm-nand-afm driver.
|
||
|
|
|
||
|
|
* STM_NAND_AFM_CACHED: Perform page reads via a cache-line. This option reduces
|
||
|
|
the impact of STBus latencies at the expense of an increased IRQ latency.
|
||
|
|
|
||
|
|
* STM_NAND_AFM_BOOTMODESUPPORT: Enable support for boot-mode ECC data (reading,
|
||
|
|
writing, and scanning bad-blocks). Support for boot-mode ECC is tied to a
|
||
|
|
specified MTD partition name (see below).
|
||
|
|
|
||
|
|
* STM_NAND_AFM_BOOTPARTITION: The name of the NAND boot partition. This can be
|
||
|
|
overridden on the kernel command line, using "nbootpart=<mtd_name>". By
|
||
|
|
default, boot-mode ECC is assumed to apply to the entire boot-partition.
|
||
|
|
|
||
|
|
* STM_NAND_AFM_PBLBOOTBOUNDARY: Select this option if using the PBL as the
|
||
|
|
boot-loader. The PBL boot-image contains both boot-mode ECC data and AFM4-ECC
|
||
|
|
data. The boundary between ECC schemes is embedded in the PBL image itself.
|
||
|
|
This option attempts to extract the boot-boundary from the PBL image, and
|
||
|
|
updates the extent to which boot-mode ECC applies within the boot-partition.
|
||
|
|
|