Summary
|
=======
|
|
This document covers various features of the 'am335x_evm' build, and some of
|
the related build targets (am335x_evm_uartN, etc).
|
|
Hardware
|
========
|
|
The binary produced by this board supports, based on parsing of the EEPROM
|
documented in TI's reference designs:
|
- AM335x GP EVM
|
- AM335x EVM SK
|
- Beaglebone White
|
- Beaglebone Black
|
|
Customization
|
=============
|
|
Given that all of the above boards are reference platforms (and the
|
Beaglebone platforms are OSHA), it is likely that this platform code and
|
configuration will be used as the basis of a custom platform. It is
|
worth noting that aside from things such as NAND or MMC only being
|
required if a custom platform makes use of these blocks, the following
|
are required, depending on design:
|
|
- GPIO is only required if DDR3 power is controlled in a way similar to
|
EVM SK
|
- SPI is only required for SPI flash, or exposing the SPI bus.
|
|
The following blocks are required:
|
- I2C, to talk with the PMIC and ensure that we do not run afoul of
|
errata 1.0.24.
|
|
When removing options as part of customization,
|
CONFIG_EXTRA_ENV_SETTINGS will need additional care to update for your
|
needs and to remove no longer relevant options as in some cases we
|
define additional text blocks (such as for NAND or DFU strings). Also
|
note that all of the SPL options are grouped together, rather than with
|
the IP blocks, so both areas will need their choices updated to reflect
|
the custom design.
|
|
NAND
|
====
|
|
The AM335x GP EVM ships with a 256MiB NAND available in most profiles. In
|
this example to program the NAND we assume that an SD card has been
|
inserted with the files to write in the first SD slot and that mtdparts
|
have been configured correctly for the board. All images are first loaded
|
into memory, then written to NAND.
|
|
Step-1: Building u-boot for NAND boot
|
Set following CONFIGxx options for NAND device.
|
CONFIG_SYS_NAND_PAGE_SIZE number of main bytes in NAND page
|
CONFIG_SYS_NAND_OOBSIZE number of OOB bytes in NAND page
|
CONFIG_SYS_NAND_BLOCK_SIZE number of bytes in NAND erase-block
|
CONFIG_SYS_NAND_ECCPOS ECC map for NAND page
|
CONFIG_NAND_OMAP_ECCSCHEME (refer doc/README.nand)
|
|
Step-2: Flashing NAND via MMC/SD
|
# select BOOTSEL to MMC/SD boot and boot from MMC/SD card
|
U-Boot # mmc rescan
|
# erase flash
|
U-Boot # nand erase.chip
|
U-Boot # env default -f -a
|
U-Boot # saveenv
|
# flash MLO. Redundant copies of MLO are kept for failsafe
|
U-Boot # load mmc 0 0x82000000 MLO
|
U-Boot # nand write 0x82000000 0x00000 0x20000
|
U-Boot # nand write 0x82000000 0x20000 0x20000
|
U-Boot # nand write 0x82000000 0x40000 0x20000
|
U-Boot # nand write 0x82000000 0x60000 0x20000
|
# flash u-boot.img
|
U-Boot # load mmc 0 0x82000000 u-boot.img
|
U-Boot # nand write 0x82000000 0x80000 0x60000
|
# flash kernel image
|
U-Boot # load mmc 0 0x82000000 uImage
|
U-Boot # nand write 0x82000000 ${nandsrcaddr} ${nandimgsize}
|
# flash filesystem image
|
U-Boot # load mmc 0 0x82000000 filesystem.img
|
U-Boot # nand write 0x82000000 ${loadaddress} 0x300000
|
|
Step-3: Set BOOTSEL pin to select NAND boot, and POR the device.
|
The device should boot from images flashed on NAND device.
|
|
NOR
|
===
|
|
The Beaglebone White can be equipped with a "memory cape" that in turn can
|
have a NOR module plugged into it. In this case it is then possible to
|
program and boot from NOR. Note that due to how U-Boot is designed we
|
must build a specific version of U-Boot that knows we have NOR flash. This
|
build is named 'am335x_evm_nor'. Further, we have a 'am335x_evm_norboot'
|
build that will assume that the environment is on NOR rather than NAND. In
|
the following example we assume that and SD card has been populated with
|
MLO and u-boot.img from a 'am335x_evm_nor' build and also contains the
|
'u-boot.bin' from a 'am335x_evm_norboot' build. When booting from NOR, a
|
binary must be written to the start of NOR, with no header or similar
|
prepended. In the following example we use a size of 512KiB (0x80000)
|
as that is how much space we set aside before the environment, as per
|
the config file.
|
|
U-Boot # mmc rescan
|
U-Boot # load mmc 0 ${loadaddr} u-boot.bin
|
U-Boot # protect off 08000000 +80000
|
U-Boot # erase 08000000 +80000
|
U-Boot # cp.b ${loadaddr} 08000000 ${filesize}
|
|
Falcon Mode
|
===========
|
|
The default build includes "Falcon Mode" (see doc/README.falcon) via NAND,
|
eMMC (or raw SD cards) and FAT SD cards. Our default behavior currently is
|
to read a 'c' on the console while in SPL at any point prior to loading the
|
OS payload (so as soon as possible) to opt to booting full U-Boot. Also
|
note that while one can program Falcon Mode "in place" great care needs to
|
be taken by the user to not 'brick' their setup. As these are all eval
|
boards with multiple boot methods, recovery should not be an issue in this
|
worst-case however.
|
|
Falcon Mode: eMMC
|
=================
|
|
The recommended layout in this case is:
|
|
MMC BLOCKS |--------------------------------| LOCATION IN BYTES
|
0x0000 - 0x007F : MBR or GPT table : 0x000000 - 0x020000
|
0x0080 - 0x00FF : ARGS or FDT file : 0x010000 - 0x020000
|
0x0100 - 0x01FF : SPL.backup1 (first copy used) : 0x020000 - 0x040000
|
0x0200 - 0x02FF : SPL.backup2 (second copy used) : 0x040000 - 0x060000
|
0x0300 - 0x06FF : U-Boot : 0x060000 - 0x0e0000
|
0x0700 - 0x08FF : U-Boot Env + Redundant : 0x0e0000 - 0x120000
|
0x0900 - 0x28FF : Kernel : 0x120000 - 0x520000
|
|
Note that when we run 'spl export' it will prepare to boot the kernel.
|
This includes relocation of the uImage from where we loaded it to the entry
|
point defined in the header. As these locations overlap by default, it
|
would leave us with an image that if written to MMC will not boot, so
|
instead of using the loadaddr variable we use 0x81000000 in the following
|
example. In this example we are loading from the network, for simplicity,
|
and assume a valid partition table already exists and 'mmc dev' has already
|
been run to select the correct device. Also note that if you previously
|
had a FAT partition (such as on a Beaglebone Black) it is not enough to
|
write garbage into the area, you must delete it from the partition table
|
first.
|
|
# Ensure we are able to talk with this mmc device
|
U-Boot # mmc rescan
|
U-Boot # tftp 81000000 am335x/MLO
|
# Write to two of the backup locations ROM uses
|
U-Boot # mmc write 81000000 100 100
|
U-Boot # mmc write 81000000 200 100
|
# Write U-Boot to the location set in the config
|
U-Boot # tftp 81000000 am335x/u-boot.img
|
U-Boot # mmc write 81000000 300 400
|
# Load kernel and device tree into memory, perform export
|
U-Boot # tftp 81000000 am335x/uImage
|
U-Boot # run findfdt
|
U-Boot # tftp ${fdtaddr} am335x/${fdtfile}
|
U-Boot # run mmcargs
|
U-Boot # spl export fdt 81000000 - ${fdtaddr}
|
# Write the updated device tree to MMC
|
U-Boot # mmc write ${fdtaddr} 80 80
|
# Write the uImage to MMC
|
U-Boot # mmc write 81000000 900 2000
|
|
Falcon Mode: FAT SD cards
|
=========================
|
|
In this case the additional file is written to the filesystem. In this
|
example we assume that the uImage and device tree to be used are already on
|
the FAT filesystem (only the uImage MUST be for this to function
|
afterwards) along with a Falcon Mode aware MLO and the FAT partition has
|
already been created and marked bootable:
|
|
U-Boot # mmc rescan
|
# Load kernel and device tree into memory, perform export
|
U-Boot # load mmc 0:1 ${loadaddr} uImage
|
U-Boot # run findfdt
|
U-Boot # load mmc 0:1 ${fdtaddr} ${fdtfile}
|
U-Boot # run mmcargs
|
U-Boot # spl export fdt ${loadaddr} - ${fdtaddr}
|
|
This will print a number of lines and then end with something like:
|
Using Device Tree in place at 80f80000, end 80f85928
|
Using Device Tree in place at 80f80000, end 80f88928
|
So then you:
|
|
U-Boot # fatwrite mmc 0:1 0x80f80000 args 8928
|
|
Falcon Mode: NAND
|
=================
|
|
In this case the additional data is written to another partition of the
|
NAND. In this example we assume that the uImage and device tree to be are
|
already located on the NAND somewhere (such as filesystem or mtd partition)
|
along with a Falcon Mode aware MLO written to the correct locations for
|
booting and mtdparts have been configured correctly for the board:
|
|
U-Boot # nand read ${loadaddr} kernel
|
U-Boot # load nand rootfs ${fdtaddr} /boot/am335x-evm.dtb
|
U-Boot # run nandargs
|
U-Boot # spl export fdt ${loadaddr} - ${fdtaddr}
|
U-Boot # nand erase.part u-boot-spl-os
|
U-Boot # nand write ${fdtaddr} u-boot-spl-os
|
