// 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], }; 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; } 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; } int memcons_getc(void) { int c; while (1) { c = memcons_getc_poll(); if (c == -1) cpu_relax(); else break; } return c; } void udbg_init_memcons(void) { udbg_putc = memcons_putc; udbg_getc = memcons_getc; udbg_getc_poll = memcons_getc_poll; }