[PATCH 1/9] arm64: meson: Add s4 SoC support

Add support for amlogic s4 (S805X2/S905W2/S905Y4) SoCs. These are very
similar to other recent SoCs, with the exception of a workaround for
some BL2 (mis)behavior.

Signed-off-by: Sean Anderson <[email protected]>
---

 arch/arm/include/asm/arch-meson/boot0.h | 14 +++++++
 arch/arm/mach-meson/Kconfig             |  7 ++++
 arch/arm/mach-meson/Makefile            |  1 +
 arch/arm/mach-meson/board-s4.c          | 50 +++++++++++++++++++++++++
 4 files changed, 72 insertions(+)
 create mode 100644 arch/arm/include/asm/arch-meson/boot0.h
 create mode 100644 arch/arm/mach-meson/board-s4.c

diff --git a/arch/arm/include/asm/arch-meson/boot0.h b/arch/arm/include/asm/arch-meson/boot0.h
new file mode 100644
index 00000000000..7338171be15
--- /dev/null
+++ b/arch/arm/include/asm/arch-meson/boot0.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2026 Brivo Systems LLC
+ */
+b reset
+#if IS_ENABLED(CONFIG_MESON_S4)
+/*
+ * BL2 copies some keys to the start of DRAM, clobbering anything in the first
+ * 2k aside from the initial instruction. I measured the actual data clobbered
+ * as 1076 bytes, but I suspect the amount depends on the configuration, so
+ * just go with what amlogic does.
+ */
+.skip 2048
+#endif
diff --git a/arch/arm/mach-meson/Kconfig b/arch/arm/mach-meson/Kconfig
index c687ef822a2..91d1e8342e0 100644
--- a/arch/arm/mach-meson/Kconfig
+++ b/arch/arm/mach-meson/Kconfig
@@ -67,6 +67,13 @@ config MESON_A1
 	help
 	  Select this if your SoC is an A113L
 
+config MESON_S4
+	bool "S4"
+	select MESON64_COMMON
+	select ENABLE_ARM_SOC_BOOT0_HOOK
+	help
+	  Select this if your SoC is an S905Y4/S905W2/S805X2
+
 endchoice
 
 config SYS_SOC
diff --git a/arch/arm/mach-meson/Makefile b/arch/arm/mach-meson/Makefile
index 08a24d4b24f..2157c35c2d5 100644
--- a/arch/arm/mach-meson/Makefile
+++ b/arch/arm/mach-meson/Makefile
@@ -17,3 +17,4 @@ endif
 obj-$(CONFIG_MESON_AXG) += board-axg.o
 obj-$(CONFIG_MESON_G12A) += board-g12a.o
 obj-$(CONFIG_MESON_A1) += board-a1.o
+obj-$(CONFIG_MESON_S4) += board-s4.o
diff --git a/arch/arm/mach-meson/board-s4.c b/arch/arm/mach-meson/board-s4.c
new file mode 100644
index 00000000000..7d0bea9924f
--- /dev/null
+++ b/arch/arm/mach-meson/board-s4.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2023 SberDevices, Inc.
+ */
+
+#include <asm/armv8/mmu.h>
+#include <asm/io.h>
+#include <linux/compiler.h>
+#include <linux/errno.h>
+
+void meson_init_reserved_memory(__maybe_unused void *fdt)
+{
+}
+
+int meson_get_boot_device(void)
+{
+	return -ENOSYS;
+}
+
+static struct mm_region s4_mem_map[] = {
+	{
+		.virt = 0x00000000UL,
+		.phys = 0x00000000UL,
+		.size = 0x80000000UL,
+		.attrs = PTE_BLOCK_MEMTYPE(MT_NORMAL) |
+			PTE_BLOCK_INNER_SHARE
+	}, {
+		.virt = 0x80000000UL,
+		.phys = 0x80000000UL,
+		.size = 0x7FE00000UL,
+		.attrs = PTE_BLOCK_MEMTYPE(MT_DEVICE_NGNRNE) |
+			PTE_BLOCK_NON_SHARE |
+			PTE_BLOCK_PXN | PTE_BLOCK_UXN
+	}, {
+		/*
+		 * This mem region contains in/out shared memory with bl31,
+		 * hence it's marked as NORMAL memory type
+		 */
+		.virt = 0xFFE00000UL,
+		.phys = 0xFFE00000UL,
+		.size = 0x00200000UL,
+		.attrs = PTE_BLOCK_MEMTYPE(MT_NORMAL) |
+			PTE_BLOCK_INNER_SHARE
+	}, {
+		/* List terminator */
+		0,
+	}
+};
+
+struct mm_region *mem_map = s4_mem_map;
-- 
2.53.0