1/*
2 * Copyright (c) 2021-2023, Stephan Gerhold <stephan@gerhold.net>
3 *
4 * Based on aarch32/skeleton_console.S:
5 * Copyright (c) 2016-2020, ARM Limited and Contributors. All rights reserved.
6 *
7 * SPDX-License-Identifier: BSD-3-Clause
8 */
9
10#include <asm_macros.S>
11#include <console_macros.S>
12
13/* UART DM registers */
14#define UART_DM_DMEN		0x03c		/* DMA / data packing */
15#define UART_DM_SR		0x0a4		/* status register */
16#define UART_DM_CR		0x0a8		/* command register */
17#define UART_DM_TF		0x100		/* transmit FIFO */
18
19#define UART_DM_DMEN_TX_SC	BIT_32(4)	/* TX single character mode */
20
21#define UART_DM_SR_TXRDY	BIT_32(2)	/* TX FIFO has space */
22#define UART_DM_SR_TXEMT	BIT_32(3)	/* TX FIFO is empty */
23
24#define UART_DM_CR_RESET_RX	(U(0x01) << 4)	/* reset receiver */
25#define UART_DM_CR_RESET_TX	(U(0x02) << 4)	/* reset transmitter */
26#define UART_DM_CR_TX_ENABLE	BIT_32(2)	/* enable transmitter */
27
28	.globl	console_uartdm_register
29	.globl	console_uartdm_core_init
30	.globl	console_uartdm_putc
31	.globl	console_uartdm_core_putc
32	.globl	console_uartdm_flush
33	.globl	console_uartdm_core_flush
34
35	/* -----------------------------------------------------------
36	 * int console_uartdm_register(console_t *console,
37	 * 	uintptr_t base_addr)
38	 * Function to initialize and register the console. The caller
39	 * needs to pass an empty console_t structure in which *MUST*
40	 * be allocated in persistent memory (e.g. a global or static
41	 * local variable, *NOT* on the stack).
42	 * In : r0 - pointer to empty console_t structure
43	 *      r1 - base address
44	 * Out: r0 - 1 on success, 0 on error
45	 * Clobber list : r0 - r7
46	 * -----------------------------------------------------------
47	 */
48func console_uartdm_register
49	str	r1, [r0, #CONSOLE_T_BASE]
50	mov	r7, lr
51	bl	console_uartdm_core_init
52	mov	lr, r7
53
54	/* Register the new console */
55	finish_console_register uartdm putc=1, flush=1
56endfunc console_uartdm_register
57
58	/* -----------------------------------------------------------
59	 * void console_uartdm_core_init(unused, uintptr_t base_addr)
60	 * Function to initialize the console.
61	 * In : r0 - unused
62	 *      r1 - base address
63	 * Out: void
64	 * Clobber list : r1, r2, r3
65	 * -----------------------------------------------------------
66	 */
67func console_uartdm_core_init
68	/*
69	 * Try to flush remaining characters from the TX FIFO before resetting
70	 * the transmitter. Unfortunately there is no good way to check if
71	 * the transmitter is actually enabled (and will finish eventually),
72	 * so use a timeout to avoid looping forever.
73	 */
74	mov	r2, #65536
751:
76	ldr	r3, [r1, #UART_DM_SR]
77	tst	r3, #UART_DM_SR_TXEMT
78	bne	2f
79	subs	r2, r2, #1
80	bne	1b
81	/* Timeout */
82
832:	/* Reset receiver */
84	mov	r3, #UART_DM_CR_RESET_RX
85	str	r3, [r1, #UART_DM_CR]
86
87	/* Reset transmitter */
88	mov	r3, #UART_DM_CR_RESET_TX
89	str	r3, [r1, #UART_DM_CR]
90
91	/*
92	 * Disable BAM/DMA modes but enable single-character mode for TX.
93	 * The single character mode allows simplifying the putc implementation
94	 * since characters can be written directly to the FIFO instead of
95	 * having to initiate a new transfer and waiting for its completion.
96	 */
97	mov	r3, #UART_DM_DMEN_TX_SC
98	str	r3, [r1, #UART_DM_DMEN]
99
100	/* Enable transmitter */
101	mov	r3, #UART_DM_CR_TX_ENABLE
102	str	r3, [r1, #UART_DM_CR]
103
104	bx	lr
105endfunc console_uartdm_core_init
106
107	/* -----------------------------------------------------------
108	 * int console_uartdm_putc(int c, console_t *console)
109	 * Function to output a character over the console.
110	 * In : r0 - character to be printed
111	 *      r1 - pointer to console_t struct
112	 * Out: r0 - printed character on success, < 0 on error.
113	 * Clobber list : r0, r1, r2
114	 * -----------------------------------------------------------
115	 */
116func console_uartdm_putc
117	ldr	r1, [r1, #CONSOLE_T_BASE]
118	b	console_uartdm_core_putc
119endfunc console_uartdm_putc
120
121	/* -----------------------------------------------------------
122	 * int console_uartdm_core_putc(int c, uintptr_t base_addr)
123	 * Function to output a character over the console.
124	 * In : r0 - character to be printed
125	 *      r1 - base address
126	 * Out: r0 - printed character on success, < 0 on error.
127	 * Clobber list : r2
128	 * -----------------------------------------------------------
129	 */
130func console_uartdm_core_putc
131	cmp	r0, #'\n'
132	bne	2f
133
1341:	/* Loop until TX FIFO has space */
135	ldr	r2, [r1, #UART_DM_SR]
136	tst	r2, #UART_DM_SR_TXRDY
137	beq	1b
138
139	/* Prepend '\r' to '\n' */
140	mov	r2, #'\r'
141	str	r2, [r1, #UART_DM_TF]
142
1432:	/* Loop until TX FIFO has space */
144	ldr	r2, [r1, #UART_DM_SR]
145	tst	r2, #UART_DM_SR_TXRDY
146	beq	2b
147
148	/* Write character to FIFO */
149	str	r0, [r1, #UART_DM_TF]
150	bx	lr
151endfunc console_uartdm_core_putc
152
153	/* -----------------------------------------------------------
154	 * void console_uartdm_flush(console_t *console)
155	 * Function to force a write of all buffered data
156	 * that has not been output.
157	 * In : r0 - pointer to console_t struct
158	 * Out: void
159	 * Clobber list : r0, r1, r2, r3, r4, r5
160	 * -----------------------------------------------------------
161	 */
162func console_uartdm_flush
163	ldr	r1, [r0, #CONSOLE_T_BASE]
164	b	console_uartdm_core_flush
165endfunc console_uartdm_flush
166
167	/* -----------------------------------------------------------
168	 * void console_uartdm_core_flush(unused, uintptr_t base_addr)
169	 * Function to force a write of all buffered data
170	 * that has not been output.
171	 * In : r0 - unused
172	 *      r1 - base address
173	 * Out: void
174	 * Clobber list : r2
175	 * -----------------------------------------------------------
176	 */
177func console_uartdm_core_flush
1781:	/* Loop until TX FIFO is empty */
179	ldr	r2, [r1, #UART_DM_SR]
180	tst	r2, #UART_DM_SR_TXEMT
181	beq	1b
182	bx	lr
183endfunc console_uartdm_core_flush
184