Blinking LED - Assembly - Raspberry Pi4

blinking_led_pi4_32bit.s

//.section .init

//=====================================
// LED Blink -frist try
// Markus Liechti
//
// For Raspberry Pi 4 
// BCM2711 (Cortex-A72 / ARM-V8)
//=====================================

//=====================================
//
// Documentation P4 (BCM2711): https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2711/rpi_DATA_2711_1p0.pdf
// Documentation P3 (BCM2837B0) https://www.raspberrypi.org/documentation/hardware/computemodule/datasheets/rpi_DATA_CM3plus_1p0.pdf
// Documentation ARM v8: https://documentation-service.arm.com/static/5f10674f0daa596235e7ecbf?token=
// -------------------------------------------------------
// Situation
//
// Use GPIO21 (PIN40) and GND (PIN39)
//
// Each GPIO (PIN) is controlled by three registers (a SELECT,a SET,a CLEAR register)
// To interact we need the physical addresses of this registers. These can be created by adding the offset and the BASE address
//
// Responsible for GPIO21 are the following registers:
// - GPFSEL2 [Offset: 0x08] responsible for GPIO Pins 20 to 29 -> our Field Name for GPIO21 is = FSEL21
// - GPCLR0 [Offset: 0x28] responsible for GPIO Pins (0 to 31) -> our Field Name for GPIO21 is = CLR21
// - GPSET0 [Offest: 0x1C] responsible for GPIO Pins (0 to 31) -> our Field Name for GPIO21 is = SET21


.global _start

//---------------------
//Setup values

.equ BASE, 0x3f200000                  // Base address of peripherials 
.equ GPFSEL2,0x08                      // Hex 8 is in binary -> 1000
.equ GPCLR0,0x28
.equ GPSET0,0x1c
.equ SET_GPFSEL2_OFFSET,0b1000         //  in Hex would be 0x08
.equ SET_GPCLR0_OFFSET,0x200000        //  offset for GPIO21 -> Offset for GPIO22 is 0x400000

_start:

    //------------------------------------------------------------------
    // Define BASE
    //------------------------------------------------------------------
    ldr r0,=BASE                       // load BASE physical address

    //------------------------------------------------------------------
    // Set the GPIO21 PIN as OUTPUT
    //------------------------------------------------------------------
    ldr r1,=SET_GPFSEL2_OFFSET         // load Offset for GPIO21 SELECT address
    str r1,[r0,#GPFSEL2]               // store value in r1 to memory at address r0 with the offset of #GPFSEL2
    //-----------------------------------------------------------------
    //-----------------------------------------------------------------
    // Turn on voltag on the GPIO21 PIN 
    //-----------------------------------------------------------------
    ldr r1,=SET_GPCLR0_OFFSET          @ load Offset for PIN 21 into r1
    str r1,[r0,#GPFSET0]               @ store value in r1 to memory at address r0 with the offset of #GPCLR0

makefile

CC = arm-none-eabi-gcc    # specify the compiler executable
CCLD = arm-none-eabi-ld   # arm gcc load
CODE = ledblinking.s      # store filename in var
OBJ = ledblinking.o       # store object filename in var
EXC = ledblinking          #

# Specify target ARM processor with "-mcpu" option
# Raspberry Pi 4   => "cortex-a72"
# Raspberry Pi 3B  => "cortex-a53"
# Raspberry Pi 2   => "cortex-a7"
TRG_ARCH = cortex-a72

# Wrap cc flags in variable
CFLAGS = -mcpu=$(TRG_ARCH) 

all: $(EXC)

$(EXC) : $(OBJ)
	$(CCLOAD) $^ -o $@	

$(OBJ): $(CODE)
	# only compile -> "-c" 
	# See: https://gcc.gnu.org/onlinedocs/gcc-10.2.0/gcc/Overall-Options.html#Overall-Options 
	# Next line is the came as: $(CC) $(CFLAGS) $(CODE) -o $(OBJ)
	# $^ = source file; $@ traget file
	$(CC) $(CFLAGS) $^ -o $@

While compiling the blinking_led_pi4 file, I get the following error: ledblinking.s: Assembler messages: ledblinking.s:59: Error: internal_relocation (type: OFFSET_IMM) not fixed up make: *** [makefile:26: ledblinking.o] Error 1
Can you help me?

Anyone who might need a full version that can blink any GPIO PIN have a look at this.