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lolserial_asm: fix accidental register corruption in debug builds, code improvements

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rw-r-r-0644 2021-05-30 20:12:38 +02:00
parent ef5565ada8
commit b16cca5a8c
1 changed files with 51 additions and 46 deletions
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93
stage2/lolserial_asm.S
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@ -27,72 +27,77 @@
.equ LOLSERIAL_WAIT_TICKS, 200
.equ GP_SENSORBAR, 0x00000100
.equ GP_SENSORBAR_SHIFT, 8
@ arg:r0 string address
lolserial_print:
mov r1, #-1
@ arg:r0 string address
@ arg:r1 max length
lolserial_lprint:
push {r5-r6}
add r1, r1, r0
push {r4-r5}
add r1, r0 @ end address in r1
ldr r5, =LT_REG_BASE @ latte registers base in r5
ldr r6, =0x0D800000
@ clear32(LT_GPIO_OWNER, GP_SENSORBAR)
ldr r2, [r5, #0x0FC]
bic r2, r2, #GP_SENSORBAR
str r2, [r5, #0x0FC]
/* clear32(LT_GPIO_OWNER, GP_SENSORBAR) */
ldr r5, [r6, #0x0FC]
bic r5, r5, #GP_SENSORBAR
str r5, [r6, #0x0FC]
@ set32(LT_GPIO_ENABLE, GP_SENSORBAR)
ldr r2, [r5, #0x0DC]
orr r2, r2, #GP_SENSORBAR
str r2, [r5, #0x0DC]
/* set32(LT_GPIO_ENABLE, GP_SENSORBAR) */
ldr r5, [r6, #0x0DC]
orr r5, r5, #GP_SENSORBAR
str r5, [r6, #0x0DC]
@ set32(LT_GPIO_DIR, GP_SENSORBAR)
ldr r2, [r5, #0x0E4]
orr r2, r2, #GP_SENSORBAR
str r2, [r5, #0x0E4]
/* set32(LT_GPIO_DIR, GP_SENSORBAR) */
ldr r5, [r6, #0x0E4]
orr r5, r5, #GP_SENSORBAR
str r5, [r6, #0x0E4]
/* set32(LT_GPIO_OUT, GP_SENSORBAR) */
ldr r5, [r6, #0x0E0]
orr r5, r5, #GP_SENSORBAR
str r5, [r6, #0x0E0]
@ set32(LT_GPIO_OUT, GP_SENSORBAR)
ldr r2, [r5, #0x0E0]
orr r2, r2, #GP_SENSORBAR
str r2, [r5, #0x0E0]
lolserial_send_string_loop:
cmp r0, r1
ldrneb r5, [r0], #1
cmpne r5, #0
cmp r0, r1 @ ensure end address was not reached
ldrneb r3, [r0], #1 @ load cur char in r3, increment r0 string ptr
cmpne r3, #0 @ check for string null termination
beq lolserial_send_string_end
mov r3, #0x200
orr r3, r3, r5, lsl #1
@ r3: bits to send (serial end bit, data byte, serial start bit)
@ r3 = (1 << 9) | (r3:chr << 1) | (0 << 0)
lsl r3, #1
orr r3, #0x200
@ loop over bits to send
lolserial_send_char_loop:
and r4, r3, #1
@ mask32(LT_GPIO_OUT, GP_SENSORBAR, bit ? GP_SENSORBAR : 0)
tst r3, #1
ldr r2, [r5, #0x0E0]
biceq r2, #GP_SENSORBAR
orrne r2, #GP_SENSORBAR
str r2, [r5, #0x0E0]
ldr r5, [r6, #0x0E0]
bic r5, r5, #GP_SENSORBAR
orr r5, r5, r4, lsl #GP_SENSORBAR_SHIFT
str r5, [r6, #0x0E0]
ldr r5, [r6, #0x010]
adds r4, r5, #LOLSERIAL_WAIT_TICKS
bcc timer_wait_loop
@ wait for LOLSERIAL_WAIT_TICKS timer ticks
ldr r2, [r5, #0x010] @ r2: current ticks
adds r4, r2, #LOLSERIAL_WAIT_TICKS @ r4: wait time end
timer_wait_overflow_loop:
ldr r2, [r6, #0x010]
cmp r2, r5
bhs timer_wait_overflow_loop
cmp r4, r2
ldr r2, [r5, #0x010]
blo timer_wait_overflow_loop
timer_wait_loop:
ldr r5, [r6, #0x010]
cmp r5, r4
blo timer_wait_loop
cmp r4, r2
ldr r2, [r5, #0x010]
bhi timer_wait_loop
movs r3, r3, lsr #1
bne lolserial_send_char_loop
lsrs r3, #1 @ go to next bit
bne lolserial_send_char_loop @ unless r3 is 0 (end bit sent)
b lolserial_send_string_loop
lolserial_send_string_end:
pop {r5-r6}
pop {r4-r5}
bx lr
#endif /* LOLSERIAL_DEBUG */