arm64: add better and more generic spin-table support

There are two enable methods supported by ARM64 Linux; psci and
spin-table.  The latter is simpler and helpful for quick SoC bring
up.  My main motivation for this patch is to improve the spin-table
support, which allows us to boot an ARMv8 system without the ARM
Trusted Firmware.

Currently, we have multi-entry code in arch/arm/cpu/armv8/start.S
and the spin-table is supported in a really ad-hoc way, and I see
some problems:

  - We must hard-code CPU_RELEASE_ADDR so that it matches the
    "cpu-release-addr" property in the DT that comes from the
    kernel tree.

  - The Documentation/arm64/booting.txt in Linux requires that
    the release address must be zero-initialized, but it is not
    cared by the common code in U-Boot.  We must do it in a board
    function.

  - There is no systematic way to protect the spin-table code from
    the kernel.  We are supposed to do it in a board specific manner,
    but it is difficult to predict where the spin-table code will be
    located after the relocation.  So, it also makes difficult to
    hard-code /memreserve/ in the DT of the kernel.

So, here is a patch to solve those problems; the DT is run-time
modified to reserve the spin-table code (+ cpu-release-addr).
Also, the "cpu-release-addr" property is set to an appropriate
address after the relocation, which means we no longer need the
hard-coded CPU_RELEASE_ADDR.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/arch/arm/cpu/armv8/spin_table.c b/arch/arm/cpu/armv8/spin_table.c
new file mode 100644
index 0000000000..ec1c9b8ddb
--- /dev/null
+++ b/arch/arm/cpu/armv8/spin_table.c
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2016 Socionext Inc.
+ *   Author: Masahiro Yamada <yamada.masahiro@socionext.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <libfdt.h>
+#include <asm/spin_table.h>
+
+int spin_table_update_dt(void *fdt)
+{
+	int cpus_offset, offset;
+	const char *prop;
+	int ret;
+	unsigned long rsv_addr = (unsigned long)&spin_table_reserve_begin;
+	unsigned long rsv_size = &spin_table_reserve_end -
+						&spin_table_reserve_begin;
+
+	cpus_offset = fdt_path_offset(fdt, "/cpus");
+	if (cpus_offset < 0)
+		return -ENODEV;
+
+	for (offset = fdt_first_subnode(fdt, cpus_offset);
+	     offset >= 0;
+	     offset = fdt_next_subnode(fdt, offset)) {
+		prop = fdt_getprop(fdt, offset, "device_type", NULL);
+		if (!prop || strcmp(prop, "cpu"))
+			continue;
+
+		/*
+		 * In the first loop, we check if every CPU node specifies
+		 * spin-table.  Otherwise, just return successfully to not
+		 * disturb other methods, like psci.
+		 */
+		prop = fdt_getprop(fdt, offset, "enable-method", NULL);
+		if (!prop || strcmp(prop, "spin-table"))
+			return 0;
+	}
+
+	for (offset = fdt_first_subnode(fdt, cpus_offset);
+	     offset >= 0;
+	     offset = fdt_next_subnode(fdt, offset)) {
+		prop = fdt_getprop(fdt, offset, "device_type", NULL);
+		if (!prop || strcmp(prop, "cpu"))
+			continue;
+
+		ret = fdt_setprop_u64(fdt, offset, "cpu-release-addr",
+				(unsigned long)&spin_table_cpu_release_addr);
+		if (ret)
+			return -ENOSPC;
+	}
+
+	ret = fdt_add_mem_rsv(fdt, rsv_addr, rsv_size);
+	if (ret)
+		return -ENOSPC;
+
+	printf("   Reserved memory region for spin-table: addr=%lx size=%lx\n",
+	       rsv_addr, rsv_size);
+
+	return 0;
+}