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-rw-r--r--arch/powerpc/sysdev/udbg_memcons.c100
1 files changed, 100 insertions, 0 deletions
diff --git a/arch/powerpc/sysdev/udbg_memcons.c b/arch/powerpc/sysdev/udbg_memcons.c
new file mode 100644
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--- /dev/null
+++ b/arch/powerpc/sysdev/udbg_memcons.c
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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],
+};
+
+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 __init udbg_init_memcons(void)
+{
+ udbg_putc = memcons_putc;
+ udbg_getc = memcons_getc;
+ udbg_getc_poll = memcons_getc_poll;
+}