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