107 lines
4.0 KiB
Plaintext
107 lines
4.0 KiB
Plaintext
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When porting from old U-Boot the follwing steps must be taken (please complain
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if there's something missing here ;)
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- Most of the macros in include/configs/yourboard.h can be removed, espacially
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the CONFIG_COMMANDS section. The goal is to remove this file entirely, but
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for now some values are still needed here. If you think some things are better
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configured with the Kconfig system feel free to add them there.
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- The linker script needs a new section for the initcalls. The handling of the
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U-Boot command table has changed also (The commands are now sorted by the
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linker instead in runtime). To change it you need an entry like the following
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in your linker script:
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#include <asm-generic/u-boot.lds.h>
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__u_boot_cmd_start = .;
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.u_boot_cmd : { U_BOOT_CMDS }
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__u_boot_cmd_end = .;
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__u_boot_initcalls_start = .;
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.u_boot_initcalls : { INITCALLS }
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__u_boot_initcalls_end = .;
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- Rename your linker script to u-boot.lds.S and add the following entry to the
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Makefile to make sure the linker script is generated:
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extra-y += u-boot.lds
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- Register the devices present in your system in the board specific .c file.
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To see anything you at least have to register a console. In scb9328.c this
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looks like this:
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static struct device_d scb9328_serial_device = {
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.name = "imx_serial",
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.id = "cs0",
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.map_base = IMX_UART1_BASE,
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.size = 4096,
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.type = DEVICE_TYPE_CONSOLE,
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};
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static int scb9328_console_init(void)
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{
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register_device(&scb9328_serial_device);
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return 0;
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}
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- For most boards you will have to register a cfi_flash device. NAND flash
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is not ported yet.
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- Call dev_add_partition() to add an environment partition for your device:
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dev_add_partition(&cfi_dev, 0x40000, 0x20000, "env");
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This will add an area starting at 0x40000 of size 0x20000 of the device
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cfi_dev as env0.
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console_initcall(scb9328_console_init);
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- Port missing drivers. Depending on the driver this can a be rather simple
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process:
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Serial drivers
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- Declare all functions static.
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- register a device of type DEVICE_TYPE_CONSOLE
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- in your probe function fill in a struct console_device and register it
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with console_register()
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Ethernet drivers
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- Basically do the same as with serial drivers.
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- Identify the parts of the driver which handle the MAC address. There are
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now two fields in struct eth_device. get_mac_address() shall retrieve the
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MAC address from the EEPROM if one is connected. If you don't have an
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EEPROM just return -1. set_mac_address() shall set the MAC address in
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the device. All magic previously done with getenv/setenv(ethaddr) must be
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removed.
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- Add a clocksource for your system. PowerPCs have a generic decrementer
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counter, so if you have a PowerPC aou have nothing to do here. on ARM
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this is SoC dependend. See Documentation/timekeeping.txt for further
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information.
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- Adjust start.S. These files share a lot of common code, so they should be
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reworked in general. On Arm you have to fix CFG_MALLOC_LEN. Most start.S
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under cpu/arm* do a "sub r0, r0, #CFG_MALLOC_LEN". If you increase
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the malloc space the value CFG_MALLOC_LEN does not fit into the instruction.
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See cpu/arm920t/start.S how it is done.
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On PowerpC there is at least the Problem that the relocation offset is
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defined at compile time. It is easily possible to determine the address
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U-Boot is currently starting from at runtime and thus allowing it U-Boot
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to be started at any address. Look at the relocation code and replace
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TEXT_BASE with the following calculation of the runtime address:
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bl calc_source /* Calculate Source Address */
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calc_source:
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mfspr r4, LR
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subi r4, r4, (calc_source - _start)
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subi r4, r4, 0x100
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(I'm almost sure that PowerPC has a dedicated instruction for this, un-
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fortunately I know next to nothing of PowerPC assembler)
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U-Boot runs now from the address it was linked to, so on PowerPC you have
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to adjust TEXT_BASE to be in RAM. This makes the various fixup functions
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unnecessary. It also simplifies debugging because you will see the
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correct addresses in the objdump.
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