platform: Add generic FDT based platform support

We add generic FDT based platform support which provides platform
specific functionality based on the FDT passed by previous booting
stage.

By default, the generic FDT platform makes following assumptions:
1. platform FW_TEXT_START is 0x80000000
2. platform features are default
3. platform stack size is default
4. platform has no quirks or work-arounds

The above assumptions (except 1) can be overridden by adding special
platform callbacks which will be called based on the FDT root node
compatible string.

By default, we compile OpenSBI generic platform as follows:
$ make PLATFORM=generic

For a non-standard FW_TEXT_START, we can compile OpenSBI generic
platform as follows:
$ make PLATFORM=generic FW_TEXT_START=<non_standard_text_start>

Signed-off-by: Anup Patel <[email protected]>
Reviewed-by: Atish Patra <[email protected]>

1 files changed, 26 insertions, 0 deletions

diff --git a/platform/generic/include/platform_override.h b/platform/generic/include/platform_override.h
new file mode 100644
index 00000000..1262627e
--- /dev/null
+++ b/platform/generic/include/platform_override.h
@@ -0,0 +1,26 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Anup Patel <[email protected]>
+ */
+
+#ifndef __PLATFORM_OVERRIDE_H__
+#define __PLATFORM_OVERRIDE_H__
+
+#include <sbi/sbi_types.h>
+
+struct platform_override {
+	const struct fdt_match *match_table;
+	u64 (*features)(const struct fdt_match *match);
+	u64 (*tlbr_flush_limit)(const struct fdt_match *match);
+	int (*early_init)(bool cold_boot, const struct fdt_match *match);
+	int (*final_init)(bool cold_boot, const struct fdt_match *match);
+	void (*early_exit)(const struct fdt_match *match);
+	void (*final_exit)(const struct fdt_match *match);
+	int (*system_reset)(u32 reset_type, const struct fdt_match *match);
+};
+
+#endif