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

On 8/27/26 11:36 AM, Neil Armstrong wrote:
> On 8/17/26 19:15, Sean Anderson wrote:
>> 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
> 
> How different is this boot0 with the one posted for T7 at [1] ?
> 
> https://lore.kernel.org/all/[email protected]/

Should be identical. Actually, the size is the same, but I couldn't figure out how
the "kernel key" was supposed to work. So using the same boot0.h should be fine.

>> 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)
>> +{
>> +}
> 
> No reserved memory at all on S4 ?

Well, ATF is signed by amlogic and can't be modified on this platform, so the
reserved memory can't change unless you use a new version of the ATF binary.
meson-s4-s905y4-khadas-vim1s.dts just hard-codes the block of memory.

>> +
>> +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;
>