[PATCH 7/7] arm: Migrate Apple M1 to save_prev_bl_data

[Konrad Dybcio]

Mark's and Dzmitry's approaches come down to the same thing.. Let's
unify them by first removing the static keyword from the common file
to allow the variable to be reused, then renaming "reg0" to the more
sensible fw_dtb_pointer coming from the Apple file and finally remove
the mach-apple implementation of this very thing and enable the common
approach in the respective defconfig.

Only build-tested.

Signed-off-by: Konrad Dybcio <konrad.dybcio at linaro.org>
---

 arch/arm/lib/save_prev_bl_data.c    | 14 +++++++-------
 arch/arm/mach-apple/Makefile        |  1 -
 arch/arm/mach-apple/lowlevel_init.S | 17 -----------------
 configs/apple_m1_defconfig          |  1 +
 4 files changed, 8 insertions(+), 25 deletions(-)
 delete mode 100644 arch/arm/mach-apple/lowlevel_init.S

diff --git a/arch/arm/lib/save_prev_bl_data.c b/arch/arm/lib/save_prev_bl_data.c
index f7b23faf0d66..a127fec1f149 100644
--- a/arch/arm/lib/save_prev_bl_data.c
+++ b/arch/arm/lib/save_prev_bl_data.c
@@ -15,7 +15,7 @@
 #include <asm/system.h>
 #include <asm/armv8/mmu.h>
 
-static ulong reg0 __section(".data");
+ulong fw_dtb_pointer __section(".data");
 
 /**
  * Save x0 register value, assuming previous bootloader set it to
@@ -23,7 +23,7 @@ static ulong reg0 __section(".data");
  */
 void save_boot_params(ulong r0)
 {
-	reg0 = r0;
+	fw_dtb_pointer = r0;
 	save_boot_params_ret();
 }
 
@@ -51,24 +51,24 @@ int save_prev_bl_data(void)
 	int node;
 	u64 initrd_start_prop;
 
-	if (!is_addr_accessible((phys_addr_t)reg0))
+	if (!is_addr_accessible((phys_addr_t)fw_dtb_pointer))
 		return -ENODATA;
 
-	fdt_blob = (struct fdt_header *)reg0;
+	fdt_blob = (struct fdt_header *)fw_dtb_pointer;
 	if (!fdt_valid(&fdt_blob)) {
-		pr_warn("%s: address 0x%lx is not a valid fdt\n", __func__, reg0);
+		pr_warn("%s: address 0x%lx is not a valid fdt\n", __func__, fw_dtb_pointer);
 		return -ENODATA;
 	}
 
 	if (IS_ENABLED(CONFIG_SAVE_PREV_BL_FDT_ADDR))
-		env_set_addr("prevbl_fdt_addr", (void *)reg0);
+		env_set_addr("prevbl_fdt_addr", (void *)fw_dtb_pointer);
 	if (!IS_ENABLED(CONFIG_SAVE_PREV_BL_INITRAMFS_START_ADDR))
 		return 0;
 
 	node = fdt_path_offset(fdt_blob, "/chosen");
 	if (!node) {
 		pr_warn("%s: chosen node not found in device tree at addr: 0x%lx\n",
-					__func__, reg0);
+					__func__, fw_dtb_pointer);
 		return -ENODATA;
 	}
 	/*
diff --git a/arch/arm/mach-apple/Makefile b/arch/arm/mach-apple/Makefile
index 50b465b9473f..a775d8866ad4 100644
--- a/arch/arm/mach-apple/Makefile
+++ b/arch/arm/mach-apple/Makefile
@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0+
 
 obj-y += board.o
-obj-y += lowlevel_init.o
 obj-y += rtkit.o
 obj-$(CONFIG_NVME_APPLE) += sart.o
diff --git a/arch/arm/mach-apple/lowlevel_init.S b/arch/arm/mach-apple/lowlevel_init.S
deleted file mode 100644
index e1c0d91cef2c..000000000000
--- a/arch/arm/mach-apple/lowlevel_init.S
+++ /dev/null
@@ -1,17 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0+ */
-/*
- * (C) Copyright 2021 Mark Kettenis <kettenis at openbsd.org>
- */
-
-.align 8
-.global fw_dtb_pointer
-fw_dtb_pointer:
-	.quad	0
-
-.global save_boot_params
-save_boot_params:
-	/* Stash DTB pointer passed by m1n1 */
-	adr	x1, fw_dtb_pointer
-	str	x0, [x1]
-
-	b	save_boot_params_ret
diff --git a/configs/apple_m1_defconfig b/configs/apple_m1_defconfig
index b4ecf73cbc78..eb0addb741c5 100644
--- a/configs/apple_m1_defconfig
+++ b/configs/apple_m1_defconfig
@@ -3,6 +3,7 @@ CONFIG_ARCH_APPLE=y
 CONFIG_DEFAULT_DEVICE_TREE="t8103-j274"
 CONFIG_SYS_LOAD_ADDR=0x0
 CONFIG_USE_PREBOOT=y
+CONFIG_SAVE_PREV_BL_FDT_ADDR=y
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_BOARD_LATE_INIT=y
-- 
2.40.0