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void pl011_set_baud_rate(pl011_uart_t *uart, uint32_t baud_rate) {
    float divider = PL011_UART_CLOCK / (16.0f * baud_rate);
    uint16_t integer_divider = (uint16_t)divider;
    uint8_t fractional_divider = ((divider - integer_divider) * 64) + 0.5;
    mmio_write(uart->IBRD, integer_divider);        // Integer baud rate divider
    mmio_write(uart->FBRD, fractional_divider);     // Fractional baud rate divider
};

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void test(uint32_t test_var) {
    float test_div = test_var / 16;
    (void)test_div;    // squash [-Wunused-variable] warnings
    // goes off the rails here
};

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(gdb) info stack
#0  pl011_set_baud_rate (uart=0x3f201000, baud_rate=115200) at kernel/uart/pl011.c:23
#1  0x0000837c in pl011_init (uart=0x3f201000) at kernel/uart/pl011.c:49
#2  0x0000806c in uart_init () at kernel/uart/uart.c:12
#3  0x00008030 in kernel_init (r0=0, r1=0, atags=0) at kernel/boot/start.c:10
#4  0x00008008 in _start () at kernel/boot/boot.S:6
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)

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r0             0x3f201000       1059065856
r1             0x1c200  115200
r2             0x7ff    2047
r3             0x0      0
r4             0x0      0
r5             0x0      0
r6             0x0      0
r7             0x0      0
r8             0x0      0
r9             0x0      0
r10            0x0      0
r11            0x7fcc   32716
r12            0x0      0
sp             0x7fb0   0x7fb0
lr             0x837c   33660
pc             0x8248   0x8248 <pl011_set_baud_rate+20>
cpsr           0x600001d3       1610613203

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INCLUDES=include
INCLUDE_PARAMS=$(foreach d, $(INCLUDES), -I$d)

CC=arm-none-eabi-gcc

C_SOURCES:=kernel/boot/start.c kernel/uart/uart.c kernel/uart/pl011.c
AS_SOURCES:=kernel/boot/boot.S

SOURCES=$(C_SOURCES)
SOURCES+=$(AS_SOURCES)

OBJECTS=
OBJECTS+=$(C_SOURCES:.c=.o)
OBJECTS+=$(AS_SOURCES:.S=.o)


CFLAGS=-std=gnu99 -Wall -Wextra -fpic -ffreestanding -mcpu=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard
LDFLAGS=-ffreestanding -nostdlib

LIBS=-lgcc

DEBUG_FLAGS=

BINARY=kernel.bin

.PHONY: all clean debug

all: $(BINARY)

debug: DEBUG_FLAGS += -ggdb
debug: $(BINARY)

$(BINARY): $(OBJECTS)
    $(CC) -T linker.ld $(LDFLAGS) $(LIBS) $(OBJECTS) -o $(BINARY)

%.o: %.c
    $(CC) $(INCLUDE_PARAMS) $(CFLAGS) $(DEBUG_FLAGS) -c $< -o $@

%.o: %.S
    $(CC) $(INCLUDE_PARAMS) $(CFLAGS) $(DEBUG_FLAGS) -c $< -o $@

clean:
    rm $(BINARY) $(OBJECTS)

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.global	pl011_set_baud_rate
	.syntax unified
	.arm
	.fpu neon-vfpv4
	.type	pl011_set_baud_rate, %function
pl011_set_baud_rate:
	@ args = 0, pretend = 0, frame = 24
	@ frame_needed = 1, uses_anonymous_args = 0
	push	{fp, lr}
	add	fp, sp, #4
	sub	sp, sp, #24
	str	r0, [fp, #-16]
	str	r1, [fp, #-20]
	ldr	r3, [fp, #-20]
	vmov	s15, r3	@ int
	vcvt.f32.u32	s15, s15
	vmov.f32	s14, #1.6e+1
	vmul.f32	s14, s15, s14
	vldr.32	s13, .L11
	vdiv.f32	s15, s13, s14
	vstr.32	s15, [fp, #-8]
	vldr.32	s15, [fp, #-8]
	vcvt.u32.f32	s15, s15
	vmov	r3, s15	@ int
	strh	r3, [fp, #-10]	@ movhi
	ldrh	r3, [fp, #-10]
	vmov	s15, r3	@ int
	vcvt.f32.s32	s15, s15
	vldr.32	s14, [fp, #-8]
	vsub.f32	s15, s14, s15
	vldr.32	s14, .L11+4
	vmul.f32	s15, s15, s14
	vcvt.f64.f32	d16, s15
	vmov.f64	d17, #5.0e-1
	vadd.f64	d7, d16, d17
	vcvt.u32.f64	s15, d7
	vstr.32	s15, [fp, #-24]	@ int
	ldrb	r3, [fp, #-24]
	strb	r3, [fp, #-11]
	ldr	r3, [fp, #-16]
	ldr	r3, [r3, #36]
	ldrh	r2, [fp, #-10]
	mov	r1, r2
	mov	r0, r3
	bl	mmio_write(PLT)
	ldr	r3, [fp, #-16]
	ldr	r3, [r3, #40]
	ldrb	r2, [fp, #-11]	@ zero_extendqisi2
	mov	r1, r2
	mov	r0, r3
	bl	mmio_write(PLT)
	nop
	sub	sp, fp, #4
	@ sp needed
	pop	{fp, pc}
.L12:
	.align	2
.L11:
	.word	1245125376
	.word	1115684864
	.size	pl011_set_baud_rate, .-pl011_set_baud_rate