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

[Mark Kettenis]

> From: Konrad Dybcio <konrad.dybcio at linaro.org>
> Date: Fri, 24 Mar 2023 01:40:40 +0100

Hi Konrad,

> 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();

I suppose this works, but it is a bit strange sice
save_boot_params_ret is just a label that we're supposed to jump back
to, not a function.

>  }
>  
> @@ -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;
>  	}
>  	/*

And we have no use for these additional environment variables and I'd
prefer not to add them.

> 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
> 
>