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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* A udbg backend which logs messages and reads input from in memory
* buffers.
*
* The console output can be read from memcons_output which is a
* circular buffer whose next write position is stored in memcons.output_pos.
*
* Input may be passed by writing into the memcons_input buffer when it is
* empty. The input buffer is empty when both input_pos == input_start and
* *input_start == '\0'.
*
* Copyright (C) 2003-2005 Anton Blanchard and Milton Miller, IBM Corp
* Copyright (C) 2013 Alistair Popple, IBM Corp
*/
#include <linux/kernel.h>
#include <asm/barrier.h>
#include <asm/page.h>
#include <asm/processor.h>
#include <asm/udbg.h>
struct memcons {
char *output_start;
char *output_pos;
char *output_end;
char *input_start;
char *input_pos;
char *input_end;
};
static char memcons_output[CONFIG_PPC_MEMCONS_OUTPUT_SIZE];
static char memcons_input[CONFIG_PPC_MEMCONS_INPUT_SIZE];
struct memcons memcons = {
.output_start = memcons_output,
.output_pos = memcons_output,
.output_end = &memcons_output[CONFIG_PPC_MEMCONS_OUTPUT_SIZE],
.input_start = memcons_input,
.input_pos = memcons_input,
.input_end = &memcons_input[CONFIG_PPC_MEMCONS_INPUT_SIZE],
};
static void memcons_putc(char c)
{
char *new_output_pos;
*memcons.output_pos = c;
wmb();
new_output_pos = memcons.output_pos + 1;
if (new_output_pos >= memcons.output_end)
new_output_pos = memcons.output_start;
memcons.output_pos = new_output_pos;
}
static int memcons_getc_poll(void)
{
char c;
char *new_input_pos;
if (*memcons.input_pos) {
c = *memcons.input_pos;
new_input_pos = memcons.input_pos + 1;
if (new_input_pos >= memcons.input_end)
new_input_pos = memcons.input_start;
else if (*new_input_pos == '\0')
new_input_pos = memcons.input_start;
*memcons.input_pos = '\0';
wmb();
memcons.input_pos = new_input_pos;
return c;
}
return -1;
}
static int memcons_getc(void)
{
int c;
while (1) {
c = memcons_getc_poll();
if (c == -1)
cpu_relax();
else
break;
}
return c;
}
void __init udbg_init_memcons(void)
{
udbg_putc = memcons_putc;
udbg_getc = memcons_getc;
udbg_getc_poll = memcons_getc_poll;
}
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