summaryrefslogtreecommitdiff
path: root/src/soc/broadcom/cygnus/ns16550.c
blob: 3005ad2331a8940b306e867b90b0b1ca56df8140 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/*
 * This file is part of the coreboot project.
 *
 * Copyright (C) 2000 Rob Taylor, Flying Pig Systems. robt@flyingpig.com.
 * Copyright (C) Broadcom Corporation
 * Copyright (C) 2015 Google Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

#include <arch/io.h>
#include <boot/coreboot_tables.h>
#include <console/console.h>	/* for __console definition */
#include <console/uart.h>
#include <delay.h>
#include <soc/ns16550.h>

#define SYS_NS16550_CLK		100000000
#define SYS_NS16550_BAUDRATE	115200
#define MODE_X_DIV		16
#define SINGLE_CHAR_TIMEOUT	(50 * 1000)

static struct ns16550 * const regs =
	(void *)CONFIG_CONSOLE_SERIAL_UART_ADDRESS;

static int calc_divisor(void)
{
	/* Compute divisor value. Normally, we should simply return:
	 *   ns16550_clk / MODE_X_DIV / baudrate
	 * but we need to round that value by adding 0.5.
	 * Rounding is especially important at high baud rates.
	 */
	int div = MODE_X_DIV * SYS_NS16550_BAUDRATE;
	return (SYS_NS16550_CLK + div / 2) / div;
}

static void ns16550_init(void)
{
	int baud_divisor = calc_divisor();

	while (!(read32(&regs->lsr) & UART_LSR_TEMT))
		;

	write32(&regs->ier, 0);
	write32(&regs->lcr, UART_LCR_BKSE | UART_LCR_8N1);
	write32(&regs->dll, 0);
	write32(&regs->dlm, 0);
	write32(&regs->lcr, UART_LCR_8N1);
	write32(&regs->mcr, UART_MCR_DTR | UART_MCR_RTS);
	/* clear & enable FIFOs */
	write32(&regs->fcr, UART_FCR_FIFO_EN | UART_FCR_RXSR | UART_FCR_TXSR);
	write32(&regs->lcr, UART_LCR_BKSE | UART_LCR_8N1);
	write32(&regs->dll, baud_divisor & 0xff);
	write32(&regs->dlm, (baud_divisor >> 8) & 0xff);
	write32(&regs->lcr, UART_LCR_8N1);
}

static void ns16550_tx_byte(unsigned char data)
{
	while ((read32(&regs->lsr) & UART_LSR_THRE) == 0)
		;
	write32(&regs->thr, data);
}

static void ns16550_tx_flush(void)
{
	while (!(read32(&regs->lsr) & UART_LSR_TEMT))
		;
}

static int ns16550_tst_byte(void)
{
	return (read32(&regs->lsr) & UART_LSR_DR) != 0;
}

static unsigned char ns16550_rx_byte(void)
{
	unsigned long int i = SINGLE_CHAR_TIMEOUT;
	while (i-- && !ns16550_tst_byte())
		udelay(1);
	if (i)
		return read32(&regs->rbr);
	else
		return 0x0;
}

void uart_init(int idx)
{
	ns16550_init();
}

void uart_tx_byte(int idx, unsigned char data)
{
	ns16550_tx_byte(data);
}

void uart_tx_flush(int idx)
{
	ns16550_tx_flush();
}

unsigned char uart_rx_byte(int idx)
{
	return ns16550_rx_byte();
}

#ifndef __PRE_RAM__
void uart_fill_lb(void *data)
{
	struct lb_serial serial;
	serial.type = LB_SERIAL_TYPE_MEMORY_MAPPED;
	serial.baseaddr = (uintptr_t)regs;
	serial.baud = default_baudrate();
	serial.regwidth = 1;
	lb_add_serial(&serial, data);

	lb_add_console(LB_TAG_CONSOLE_SERIAL8250MEM, data);
}
#endif