Rock64 - Simple Bare-Metal Example

Rock64 - Simple Bare-Metal Example - Printable Version

+- PINE64 (https://forum.pine64.org)
+-- Forum: ROCK64 (https://forum.pine64.org/forumdisplay.php?fid=85)
+--- Forum: Rock64 Tutorials (https://forum.pine64.org/forumdisplay.php?fid=90)
+--- Thread: Rock64 - Simple Bare-Metal Example (/showthread.php?tid=10079)

Rock64 - Simple Bare-Metal Example - krjdev - 06-05-2020

Hi,

I wrote a simple Bare-Metal example for the Rock64.
It just sends a few strings over the UART interface and if a special char will be received, the program resets the Rock64.

The main entry point of the program (written in Assembler):

Code:
#include <asm.h>

IMPORT_C(kern_main)

.text

ENTRY(_start)

    mrs x0, SCTLR_EL1

    and x0, x0, #0xFFFFFFFFFFFFFFFC

    msr SCTLR_EL1, x0

    mrs x0, SCTLR_EL2

    and x0, x0, #0xFFFFFFFFFFFFFFFC

    msr SCTLR_EL2, x0

    mrs x0, MPIDR_EL1

    and x0, x0, #0x3

    cmp x0, #0

    beq L1

L0:

    wfe

    b L0

L1:

    ldr x0, =_kern_stack_s

    mov sp, x0

    b kern_main

L2:

    wfe

    b L2

.end

It's a minimal setup. It just disables the MMU and the Alignment checks.
Then it reads the processor ID and let only CPU0 run the C main entry point (kern_main).

The C main entry point:

Code:
#include <dev/cru.h>

#include <dev/uart.h>

void kern_main(void)

{

    int c;

    uart_init();

    uart_puts("Pine64 Rock64\r\n");

    uart_puts("Press 'r' to reset the board!\r\n");

    do {

        c = uart_getc();

    } while (c != 'r');

    uart_puts("Resetting...\r\n");

    cru_reset();

    while (1)

        ;

}

Should be self explaining.

There is also as very simple UART driver and the CRU driver for resetting the board.
The code includes a very minimal C String library.Only GCC for AArch64 is needed.

To start the application, U-Boot is needed.

I have attached the full code.
The code is also on my GitHub page available.

Edit:
Oops! There is a bug in the attached archive.

Simple change the following line in the file start.S...

Code:
ldr x0, =_kern_stack_s

to..

Code:
ldr x0, =_kern_stack_e

RE: Rock64 - Simple Bare-Metal Example - krjdev - 01-24-2021

Hi,

I'm currently working on a new release for the bare-metal example.

Current reached milestones:
- Successfully implemented MMU support (Had some troubles with the translation tables in the past.)
- Implemented cleaning and invalidating for the Instruction and data cache
- Switching from EL2 (Hypervisor) to EL1 (Kernel)

Currently working on the implementation of syscalls.

Feature of the new release:
- Simple kernel (EL1) for exception/interrupt handling, device and memory management
- Small libc for userland (EL0)

New release available soon. Smile

The actual status is available at the next branch.