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

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]/

> 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 ?

> +
> +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;