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

[Konrad Dybcio]

On 27.03.2023 21:31, Mark Kettenis wrote:
>> 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.
Okay, let's forget about it then.

Would you (or anybody responsible, I don't know who picks things up)
be willing to take this patch without the Apple part then, a.k.a.
renaming r0 to fw_dtb_pointer?

Konrad
> 
>> 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
>>
>>