arch/powerpc/boot/ns16550.c

Source file repositories/reference/linux-study-clean/arch/powerpc/boot/ns16550.c

File Facts

System
Linux kernel
Corpus path
arch/powerpc/boot/ns16550.c
Extension
.c
Size
2137 bytes
Lines
85
Domain
Architecture Layer
Bucket
arch/powerpc
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
/*
 * 16550 serial console support.
 *
 * Original copied from <file:arch/ppc/boot/common/ns16550.c>
 * (which had no copyright)
 * Modifications: 2006 (c) MontaVista Software, Inc.
 *
 * Modified by: Mark A. Greer <mgreer@mvista.com>
 */
#include <stdarg.h>
#include <stddef.h>
#include "types.h"
#include "string.h"
#include "stdio.h"
#include "io.h"
#include "ops.h"
#include "of.h"

#define UART_DLL	0	/* Out: Divisor Latch Low */
#define UART_DLM	1	/* Out: Divisor Latch High */
#define UART_FCR	2	/* Out: FIFO Control Register */
#define UART_LCR	3	/* Out: Line Control Register */
#define UART_MCR	4	/* Out: Modem Control Register */
#define UART_LSR	5	/* In:  Line Status Register */
#define UART_LSR_THRE	0x20	/* Transmit-hold-register empty */
#define UART_LSR_DR	0x01	/* Receiver data ready */
#define UART_MSR	6	/* In:  Modem Status Register */
#define UART_SCR	7	/* I/O: Scratch Register */

static unsigned char *reg_base;
static u32 reg_shift;

static int ns16550_open(void)
{
	out_8(reg_base + (UART_FCR << reg_shift), 0x06);
	return 0;
}

static void ns16550_putc(unsigned char c)
{
	while ((in_8(reg_base + (UART_LSR << reg_shift)) & UART_LSR_THRE) == 0);
	out_8(reg_base, c);
}

static unsigned char ns16550_getc(void)
{
	while ((in_8(reg_base + (UART_LSR << reg_shift)) & UART_LSR_DR) == 0);
	return in_8(reg_base);
}

static u8 ns16550_tstc(void)
{
	return ((in_8(reg_base + (UART_LSR << reg_shift)) & UART_LSR_DR) != 0);
}

int ns16550_console_init(void *devp, struct serial_console_data *scdp)
{
	int n;
	u32 reg_offset;

	if (dt_get_virtual_reg(devp, (void **)&reg_base, 1) < 1) {
		printf("virt reg parse fail...\r\n");
		return -1;
	}

	n = getprop(devp, "reg-offset", &reg_offset, sizeof(reg_offset));
	if (n == sizeof(reg_offset))
		reg_base += be32_to_cpu(reg_offset);

	n = getprop(devp, "reg-shift", &reg_shift, sizeof(reg_shift));
	if (n != sizeof(reg_shift))
		reg_shift = 0;
	else
		reg_shift = be32_to_cpu(reg_shift);

	scdp->open = ns16550_open;
	scdp->putc = ns16550_putc;
	scdp->getc = ns16550_getc;
	scdp->tstc = ns16550_tstc;
	scdp->close = NULL;

	return 0;
}

Annotation

Implementation Notes