tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * 16550 serial console support.
4 *
5 * Original copied from <file:arch/ppc/boot/common/ns16550.c>
6 * (which had no copyright)
7 * Modifications: 2006 (c) MontaVista Software, Inc.
8 *
9 * Modified by: Mark A. Greer <mgreer@mvista.com>
10 */
11#include <stdarg.h>
12#include <stddef.h>
13#include "types.h"
14#include "string.h"
15#include "stdio.h"
16#include "io.h"
17#include "ops.h"
18
19#define UART_DLL 0 /* Out: Divisor Latch Low */
20#define UART_DLM 1 /* Out: Divisor Latch High */
21#define UART_FCR 2 /* Out: FIFO Control Register */
22#define UART_LCR 3 /* Out: Line Control Register */
23#define UART_MCR 4 /* Out: Modem Control Register */
24#define UART_LSR 5 /* In: Line Status Register */
25#define UART_LSR_THRE 0x20 /* Transmit-hold-register empty */
26#define UART_LSR_DR 0x01 /* Receiver data ready */
27#define UART_MSR 6 /* In: Modem Status Register */
28#define UART_SCR 7 /* I/O: Scratch Register */
29
30static unsigned char *reg_base;
31static u32 reg_shift;
32
33static int ns16550_open(void)
34{
35 out_8(reg_base + (UART_FCR << reg_shift), 0x06);
36 return 0;
37}
38
39static void ns16550_putc(unsigned char c)
40{
41 while ((in_8(reg_base + (UART_LSR << reg_shift)) & UART_LSR_THRE) == 0);
42 out_8(reg_base, c);
43}
44
45static unsigned char ns16550_getc(void)
46{
47 while ((in_8(reg_base + (UART_LSR << reg_shift)) & UART_LSR_DR) == 0);
48 return in_8(reg_base);
49}
50
51static u8 ns16550_tstc(void)
52{
53 return ((in_8(reg_base + (UART_LSR << reg_shift)) & UART_LSR_DR) != 0);
54}
55
56int ns16550_console_init(void *devp, struct serial_console_data *scdp)
57{
58 int n;
59 u32 reg_offset;
60
61 if (dt_get_virtual_reg(devp, (void **)®_base, 1) < 1)
62 return -1;
63
64 n = getprop(devp, "reg-offset", ®_offset, sizeof(reg_offset));
65 if (n == sizeof(reg_offset))
66 reg_base += reg_offset;
67
68 n = getprop(devp, "reg-shift", ®_shift, sizeof(reg_shift));
69 if (n != sizeof(reg_shift))
70 reg_shift = 0;
71
72 scdp->open = ns16550_open;
73 scdp->putc = ns16550_putc;
74 scdp->getc = ns16550_getc;
75 scdp->tstc = ns16550_tstc;
76 scdp->close = NULL;
77
78 return 0;
79}