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/*
* Copyright (c) 2021-2023, Stephan Gerhold <stephan@gerhold.net>
*
* Based on aarch32/skeleton_console.S:
* Copyright (c) 2016-2020, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <asm_macros.S>
#include <console_macros.S>
/* UART DM registers */
#define UART_DM_DMEN 0x03c /* DMA / data packing */
#define UART_DM_SR 0x0a4 /* status register */
#define UART_DM_CR 0x0a8 /* command register */
#define UART_DM_TF 0x100 /* transmit FIFO */
#define UART_DM_DMEN_TX_SC BIT_32(4) /* TX single character mode */
#define UART_DM_SR_TXRDY BIT_32(2) /* TX FIFO has space */
#define UART_DM_SR_TXEMT BIT_32(3) /* TX FIFO is empty */
#define UART_DM_CR_RESET_RX (U(0x01) << 4) /* reset receiver */
#define UART_DM_CR_RESET_TX (U(0x02) << 4) /* reset transmitter */
#define UART_DM_CR_TX_ENABLE BIT_32(2) /* enable transmitter */
.globl console_uartdm_register
.globl console_uartdm_core_init
.globl console_uartdm_putc
.globl console_uartdm_core_putc
.globl console_uartdm_flush
.globl console_uartdm_core_flush
/* -----------------------------------------------------------
* int console_uartdm_register(console_t *console,
* uintptr_t base_addr)
* Function to initialize and register the console. The caller
* needs to pass an empty console_t structure in which *MUST*
* be allocated in persistent memory (e.g. a global or static
* local variable, *NOT* on the stack).
* In : r0 - pointer to empty console_t structure
* r1 - base address
* Out: r0 - 1 on success, 0 on error
* Clobber list : r0 - r7
* -----------------------------------------------------------
*/
func console_uartdm_register
str r1, [r0, #CONSOLE_T_BASE]
mov r7, lr
bl console_uartdm_core_init
mov lr, r7
/* Register the new console */
finish_console_register uartdm putc=1, flush=1
endfunc console_uartdm_register
/* -----------------------------------------------------------
* void console_uartdm_core_init(unused, uintptr_t base_addr)
* Function to initialize the console.
* In : r0 - unused
* r1 - base address
* Out: void
* Clobber list : r1, r2, r3
* -----------------------------------------------------------
*/
func console_uartdm_core_init
/*
* Try to flush remaining characters from the TX FIFO before resetting
* the transmitter. Unfortunately there is no good way to check if
* the transmitter is actually enabled (and will finish eventually),
* so use a timeout to avoid looping forever.
*/
mov r2, #65536
1:
ldr r3, [r1, #UART_DM_SR]
tst r3, #UART_DM_SR_TXEMT
bne 2f
subs r2, r2, #1
bne 1b
/* Timeout */
2: /* Reset receiver */
mov r3, #UART_DM_CR_RESET_RX
str r3, [r1, #UART_DM_CR]
/* Reset transmitter */
mov r3, #UART_DM_CR_RESET_TX
str r3, [r1, #UART_DM_CR]
/*
* Disable BAM/DMA modes but enable single-character mode for TX.
* The single character mode allows simplifying the putc implementation
* since characters can be written directly to the FIFO instead of
* having to initiate a new transfer and waiting for its completion.
*/
mov r3, #UART_DM_DMEN_TX_SC
str r3, [r1, #UART_DM_DMEN]
/* Enable transmitter */
mov r3, #UART_DM_CR_TX_ENABLE
str r3, [r1, #UART_DM_CR]
bx lr
endfunc console_uartdm_core_init
/* -----------------------------------------------------------
* int console_uartdm_putc(int c, console_t *console)
* Function to output a character over the console.
* In : r0 - character to be printed
* r1 - pointer to console_t struct
* Out: r0 - printed character on success, < 0 on error.
* Clobber list : r0, r1, r2
* -----------------------------------------------------------
*/
func console_uartdm_putc
ldr r1, [r1, #CONSOLE_T_BASE]
b console_uartdm_core_putc
endfunc console_uartdm_putc
/* -----------------------------------------------------------
* int console_uartdm_core_putc(int c, uintptr_t base_addr)
* Function to output a character over the console.
* In : r0 - character to be printed
* r1 - base address
* Out: r0 - printed character on success, < 0 on error.
* Clobber list : r2
* -----------------------------------------------------------
*/
func console_uartdm_core_putc
cmp r0, #'\n'
bne 2f
1: /* Loop until TX FIFO has space */
ldr r2, [r1, #UART_DM_SR]
tst r2, #UART_DM_SR_TXRDY
beq 1b
/* Prepend '\r' to '\n' */
mov r2, #'\r'
str r2, [r1, #UART_DM_TF]
2: /* Loop until TX FIFO has space */
ldr r2, [r1, #UART_DM_SR]
tst r2, #UART_DM_SR_TXRDY
beq 2b
/* Write character to FIFO */
str r0, [r1, #UART_DM_TF]
bx lr
endfunc console_uartdm_core_putc
/* -----------------------------------------------------------
* void console_uartdm_flush(console_t *console)
* Function to force a write of all buffered data
* that has not been output.
* In : r0 - pointer to console_t struct
* Out: void
* Clobber list : r0, r1, r2, r3, r4, r5
* -----------------------------------------------------------
*/
func console_uartdm_flush
ldr r1, [r0, #CONSOLE_T_BASE]
b console_uartdm_core_flush
endfunc console_uartdm_flush
/* -----------------------------------------------------------
* void console_uartdm_core_flush(unused, uintptr_t base_addr)
* Function to force a write of all buffered data
* that has not been output.
* In : r0 - unused
* r1 - base address
* Out: void
* Clobber list : r2
* -----------------------------------------------------------
*/
func console_uartdm_core_flush
1: /* Loop until TX FIFO is empty */
ldr r2, [r1, #UART_DM_SR]
tst r2, #UART_DM_SR_TXEMT
beq 1b
bx lr
endfunc console_uartdm_core_flush
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