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How to change the boot value of a control register with Juno?

Ali Saidi
Arm Employee Badge

Could someone suggest a way to change the boot value of a control register (e.g. ACTLR)? It seems like i'd want to do it in bl31:bl31_arch_setup(), but does each CPU go through bl31 or just the boot CPU? If I was just interested in the A7s is there a way to only boot them?

Thanks,

Ali

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  • 0 Arm Employee Badge

    The SCC General Purpose Register 1 (SCC GPR1) can be used to determine the boot CPUs. The layout of SCC GPR1 is as follows:

      0 - Crypto Disable

      1 - CFGTE

      2 - CFGEE

      3 - Boot Map Enable (default = 0)

     

      4 - A53-0

      5 - A53-1

      6 - A53-2

      7 - A53-3

      8 - A57-0

      9 - A57-1

      10 - Reserved

      11 - Reserved

      [15:12] - Primary CPU selection. Index values 0 through 5, following

      the order of cores above.

    To set the Cortex-A57 as the boot cluster and Cortex-A57_0 as the primary CPU you will need to set bit 3 to enable the boot map, set bits 8,9 to select the A57s and finally setting [15:12] to 0x4 so that Cortex-A57_0 is considered the primary CPU. You will need to add the following SCC entry to the 'board.txt' file located in "E:\SITE1\HBI0262B":

      SCC: 0x0F4 0x00004308           ;

    This will determine what CPUs are brought out of reset by the SCP. This said, the AP Trusted firmware was hardcoded to use Cortex-A53_0 as the primary CPU.

    To change the primary CPU in the AP Trusted Firmware, the PRIMARY_CPU entry in 'plat/juno/platform.h' will need to be altered. Steps describing how to re-build the AP Trusted firmware can be found on the  'Juno Software Guide ' page.

    Regarding where system configurations such as setting the ACTLR should be performed, we would recommend either cpu_reset_handler() in BL1 or it can be done in bl31_arch_setup().

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  • 0 Arm Employee Badge

    The SCC General Purpose Register 1 (SCC GPR1) can be used to determine the boot CPUs. The layout of SCC GPR1 is as follows:

      0 - Crypto Disable

      1 - CFGTE

      2 - CFGEE

      3 - Boot Map Enable (default = 0)

     

      4 - A53-0

      5 - A53-1

      6 - A53-2

      7 - A53-3

      8 - A57-0

      9 - A57-1

      10 - Reserved

      11 - Reserved

      [15:12] - Primary CPU selection. Index values 0 through 5, following

      the order of cores above.

    To set the Cortex-A57 as the boot cluster and Cortex-A57_0 as the primary CPU you will need to set bit 3 to enable the boot map, set bits 8,9 to select the A57s and finally setting [15:12] to 0x4 so that Cortex-A57_0 is considered the primary CPU. You will need to add the following SCC entry to the 'board.txt' file located in "E:\SITE1\HBI0262B":

      SCC: 0x0F4 0x00004308           ;

    This will determine what CPUs are brought out of reset by the SCP. This said, the AP Trusted firmware was hardcoded to use Cortex-A53_0 as the primary CPU.

    To change the primary CPU in the AP Trusted Firmware, the PRIMARY_CPU entry in 'plat/juno/platform.h' will need to be altered. Steps describing how to re-build the AP Trusted firmware can be found on the  'Juno Software Guide ' page.

    Regarding where system configurations such as setting the ACTLR should be performed, we would recommend either cpu_reset_handler() in BL1 or it can be done in bl31_arch_setup().

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