1/*
2 * Copyright (c) 2021, Stephan Gerhold <stephan@gerhold.net>
3 *
4 * Based on aarch64/skeleton_console.S:
5 * Copyright (c) 2015-2020, 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	2		/* TX FIFO has space */
22#define UART_DM_SR_TXEMT_BIT	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 : x0 - pointer to empty console_t structure
43	 *      x1 - base address
44	 * Out: x0 - 1 on success, 0 on error
45	 * Clobber list : x0 - x7
46	 * -----------------------------------------------------------
47	 */
48func console_uartdm_register
49	str	x1, [x0, #CONSOLE_T_BASE]
50	mov	x7, lr
51	bl	console_uartdm_core_init
52	mov	lr, x7
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 : x0 - unused
62	 *      x1 - base address
63	 * Out: void
64	 * Clobber list : x1, x2, x3
65	 * -----------------------------------------------------------
66	 */
67func console_uartdm_core_init
68	/* Reset receiver */
69	mov	w3, #UART_DM_CR_RESET_RX
70	str	w3, [x1, #UART_DM_CR]
71
72	/* Reset transmitter */
73	mov	w3, #UART_DM_CR_RESET_TX
74	str	w3, [x1, #UART_DM_CR]
75
76	/*
77	 * Disable BAM/DMA modes but enable single-character mode for TX.
78	 * The single character mode allows simplifying the putc implementation
79	 * since characters can be written directly to the FIFO instead of
80	 * having to initiate a new transfer and waiting for its completion.
81	 */
82	mov	w3, #UART_DM_DMEN_TX_SC
83	str	w3, [x1, #UART_DM_DMEN]
84
85	/* Enable transmitter */
86	mov	w3, #UART_DM_CR_TX_ENABLE
87	str	w3, [x1, #UART_DM_CR]
88
89	ret
90endfunc console_uartdm_core_init
91
92	/* -----------------------------------------------------------
93	 * int console_uartdm_putc(int c, console_t *console)
94	 * Function to output a character over the console.
95	 * In : w0 - character to be printed
96	 *      x1 - pointer to console_t struct
97	 * Out: w0 - printed character on success, < 0 on error.
98	 * Clobber list : x0, x1, x2
99	 * -----------------------------------------------------------
100	 */
101func console_uartdm_putc
102	ldr	x1, [x1, #CONSOLE_T_BASE]
103	b	console_uartdm_core_putc
104endfunc console_uartdm_putc
105
106	/* -----------------------------------------------------------
107	 * int console_uartdm_core_putc(int c, uintptr_t base_addr)
108	 * Function to output a character over the console.
109	 * In : w0 - character to be printed
110	 *      x1 - base address
111	 * Out: w0 - printed character on success, < 0 on error.
112	 * Clobber list : x2
113	 * -----------------------------------------------------------
114	 */
115func console_uartdm_core_putc
1161:	/* Loop until TX FIFO has space */
117	ldr	w2, [x1, #UART_DM_SR]
118	tbz	w2, #UART_DM_SR_TXRDY_BIT, 1b
119
120	/* Write character to FIFO */
121	str	w0, [x1, #UART_DM_TF]
122	ret
123endfunc console_uartdm_core_putc
124
125	/* -----------------------------------------------------------
126	 * void console_uartdm_flush(console_t *console)
127	 * Function to force a write of all buffered data
128	 * that has not been output.
129	 * In : x0 - pointer to console_t struct
130	 * Out: void
131	 * Clobber list : x0, x1, x2, x3, x4, x5
132	 * -----------------------------------------------------------
133	 */
134func console_uartdm_flush
135	ldr	x1, [x0, #CONSOLE_T_BASE]
136	b	console_uartdm_core_flush
137endfunc console_uartdm_flush
138
139	/* -----------------------------------------------------------
140	 * void console_uartdm_core_flush(unused, uintptr_t base_addr)
141	 * Function to force a write of all buffered data
142	 * that has not been output.
143	 * In : x0 - unused
144	 *      x1 - base address
145	 * Out: void
146	 * Clobber list : x2
147	 * -----------------------------------------------------------
148	 */
149func console_uartdm_core_flush
1501:	/* Loop until TX FIFO is empty */
151	ldr	w2, [x1, #UART_DM_SR]
152	tbz	w2, #UART_DM_SR_TXEMT_BIT, 1b
153	ret
154endfunc console_uartdm_core_flush
155