isfshax/stage2/lolserial_asm.S

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2021-05-26 01:53:11 +02:00
/*
* minute - a port of the "mini" IOS replacement for the Wii U.
*
* Copyright (C) 2021 Roberto Van Eeden <rwrr0644@gmail.com>
*
* This code is licensed to you under the terms of the GNU GPL, version 2;
* see file COPYING or http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt
*/
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#ifdef LOLSERIAL_DEBUG
#include "latte.h"
.arm
.globl lolserial_print
.globl lolserial_lprint
.section .text
/*
* the number of timer ticks to wait
* each bit; might need manual adjustment
* for particoular serial adapters, usually
* the stable value is in the +5/-5 range
*/
.equ LOLSERIAL_WAIT_TICKS, 200
.equ GP_SENSORBAR, 0x00000100
@ arg:r0 string address
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lolserial_print:
mov r1, #-1
@ arg:r0 string address
@ arg:r1 max length
lolserial_lprint:
push {r4-r5}
add r1, r0 @ end address in r1
ldr r5, =LT_REG_BASE @ latte registers base in r5
@ clear32(LT_GPIO_OWNER, GP_SENSORBAR)
ldr r2, [r5, #0x0FC]
bic r2, r2, #GP_SENSORBAR
str r2, [r5, #0x0FC]
@ set32(LT_GPIO_ENABLE, GP_SENSORBAR)
ldr r2, [r5, #0x0DC]
orr r2, r2, #GP_SENSORBAR
str r2, [r5, #0x0DC]
@ set32(LT_GPIO_DIR, GP_SENSORBAR)
ldr r2, [r5, #0x0E4]
orr r2, r2, #GP_SENSORBAR
str r2, [r5, #0x0E4]
@ set32(LT_GPIO_OUT, GP_SENSORBAR)
ldr r2, [r5, #0x0E0]
orr r2, r2, #GP_SENSORBAR
str r2, [r5, #0x0E0]
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lolserial_send_string_loop:
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
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@ 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
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@ loop over bits to send
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lolserial_send_char_loop:
@ 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]
@ wait for LOLSERIAL_WAIT_TICKS timer ticks
ldr r2, [r5, #0x010] @ r2: current ticks
adds r4, r2, #LOLSERIAL_WAIT_TICKS @ r4: wait time end
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timer_wait_overflow_loop:
cmp r4, r2
ldr r2, [r5, #0x010]
blo timer_wait_overflow_loop
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timer_wait_loop:
cmp r4, r2
ldr r2, [r5, #0x010]
bhi timer_wait_loop
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lsrs r3, #1 @ go to next bit
bne lolserial_send_char_loop @ unless r3 is 0 (end bit sent)
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b lolserial_send_string_loop
lolserial_send_string_end:
pop {r4-r5}
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bx lr
#endif /* LOLSERIAL_DEBUG */