AM335x Booting Sequence

Vip Kumar

Hi,

I am using AM335x based BeagleBone Black board. I want to know what are the steps involved in booting sequence right from the RESET/Power ON till it loads the kernel.

As per my understanding, the following sequence is followed:

The boot process begins at Power On Reset (POR) where the hardware reset logic forces the ARM core to begin execution starting from the on-chip Boot ROM.

The Boot ROM code uses the given boot select options as well as the state of various FUSE/straps and GPIO settings to determine the boot flow behavior of the SOC.

After determining the booting media,

1. What's the next step ?

2. How does Boot ROM code read and initialize the DDR settings ?

3. How do we reach the target board or customized board u-boot ?

over 9 years ago

0 Shivasharan Nagalikar over 9 years ago

TI__Expert 8480 points

Hi, please see the training materials from:
training.ti.com/sitara™-arm®-processors-boot-camp-training-series

In summary: ROM code loads reads the switch boot settings and understands the boot media. From there the MLO is fetched and execute from internal RAM and initialize the DDR and clocks to finally to get u-boot and Kernel.

Best Regards,
Shiv

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

1. ROM code reads the first stage bootloader (named MLO or SPL) from the boot media into AM335X internal SRAM and transfers execution to it.
2. MLO/SPL does further initialization, including DDR initialization, then reads U-boot from the boot media into DDR.
3. MLO/SPL transfers execution to U-boot.

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AM335x Booting Sequence