AM3358: where does u-boot fail when the board id isn't set

Stuart Woodbury

Part Number: AM3358

Devices such as a beaglebone black have a string written to eeprom that u-boot reads and uses to configure the peripherals. There is a guide about this here: OSD335x EEPROM During Boot.

If you just put an AM335X chip on a board, it won't boot linux until eeprom is flashed with the board id. My question is this: where in u-boot does it actually fail when the board id isn't set?

What I've tried so far:
I see that the board id is checked and pinmux is configured in <u-boot src>/board/ti/am335x/board.h and <u-boot src>/board/ti/mux.c.

I also found that the bootloader starts in start.S and eventually winds up in board_r.c, and loops through the commands in init_sequence_r, defined on line 679. I understand that if any of those functions fail, u-boot won't boot. I've checked some of those functions but I don't see any reference to the board id

over 5 years ago

0 Hong Guan64 over 5 years ago

TI__Guru* 75890 points

Hi Stuart,

The board_id is programmed in EEPROM, and SPL/u-boot setup board configuration (PMIC, D-PLL, DDR, pinmux…) based on the board ID detected.

board_id and specific board configuration are in board.h/board.c under <board/ti/am335x/> for AM335x.

Best,

-Hong

0 Stuart Woodbury over 5 years ago in reply to Hong Guan64

Prodigy 40 points

Hong, thanks for trying, but this doesn't answer my question.

0 Stuart Woodbury over 5 years ago in reply to Hong Guan64

Prodigy 40 points

I'm looking for the place where u-boot fails. I understand how board id is used to configure the peripherals, but I do not see where this would cause u-boot to fail. Perhaps an attempt to access unconfigured peripherals would cause a non zero return code in init_sequence_r? That's the type of thing i'm looking for.

0 Hong Guan64 over 5 years ago in reply to Stuart Woodbury

TI__Guru* 75890 points

Hi Stuart,

Depending on return from board ID detect via board_is_ID_xyz(), where for AM335x

1. in board.c (board/ti/am335x/)

- PMIC, and DPLL configuration in scale_vcore();

- DDR configuration in sdram_init();

2. in mux.c (board/ti/am335x/)

- Pinmux configuration in enable_board_pin_mux();

In-correct configuration in any of above (PMIC, DPLL, DDR, Pinmux) may potentially leads un-expected behavior, or "fail".

For example, if non-matching DDR parameters are used in sdram_init(), DDR would be un-stable, and booting would fail in board_init_f() before reaching to board_init_r();

Best,

-Hong

0 Stuart Woodbury over 5 years ago in reply to Hong Guan64

Prodigy 40 points

Hong, thanks for confirming my suspicions.

0 Hong Guan64 over 5 years ago in reply to Stuart Woodbury

TI__Guru* 75890 points

Hi Stuart,

Would you go ahead closing the issue.

Best,

-Hong

Processors

Processors forum

AM3358: where does u-boot fail when the board id isn't set