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From:   Anup Patel <anup@brainfault.org>
Date:   Tue, 5 Jan 2021 16:55:14 +0530
Message-ID: <CAAhSdy08ujtYCrSr-O0Me-UbqQTa9N6vjtqgUV3NZofnkOjFwg@mail.gmail.com>
Subject: Re: [PATCH v2] riscv: add BUILTIN_DTB support for MMU-enabled targets
To:     Vitaly Wool <vitaly.wool@konsulko.com>
Cc:     linux-riscv <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        Bin Meng <bin.meng@windriver.com>,
        Palmer Dabbelt <palmerdabbelt@google.com>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        devicetree@vger.kernel.org
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Precedence: bulk

On Mon, Jan 4, 2021 at 6:15 PM Vitaly Wool <vitaly.wool@konsulko.com> wrote:
>
> Sometimes, especially in a production system we may not want to
> use a "smart bootloader" like u-boot to load kernel, ramdisk and
> device tree from a filesystem on eMMC, but rather load the kernel
> from a NAND partition and just run it as soon as we can, and in
> this case it is convenient to have device tree compiled into the
> kernel binary. Since this case is not limited to MMU-less systems,
> let's support it for these which have MMU enabled too.
>
> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
> ---
> Changelog from v1:
> * no direct initial_boot_params assignment
> * skips the temporary mapping for DT if BUILTIN_DTB=y
>
>  arch/riscv/Kconfig   |  1 -
>  arch/riscv/mm/init.c | 15 +++++++++++++--
>  2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 81b76d44725d..07a8bdcc423f 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -416,7 +416,6 @@ endmenu
>
>  config BUILTIN_DTB
>         def_bool n
> -       depends on RISCV_M_MODE
>         depends on OF
>
>  menu "Power management options"
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 13ba533f462b..04aeee276817 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -191,10 +191,13 @@ void __init setup_bootmem(void)
>  #endif /* CONFIG_BLK_DEV_INITRD */
>
>         /*
> -        * Avoid using early_init_fdt_reserve_self() since __pa() does
> +        * If DTB is built in, no need to reserve its memblock.
> +        * Otherwise, do reserve it but avoid using
> +        * early_init_fdt_reserve_self() since __pa() does
>          * not work for DTB pointers that are fixmap addresses
>          */
> -       memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
> +       if (!IS_ENABLED(CONFIG_BUILTIN_DTB))
> +               memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
>
>         early_init_fdt_scan_reserved_mem();
>         dma_contiguous_reserve(dma32_phys_limit);
> @@ -499,6 +502,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>         /* Setup early PMD for DTB */
>         create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA,
>                            (uintptr_t)early_dtb_pmd, PGDIR_SIZE, PAGE_TABLE);
> +#ifndef CONFIG_BUILTIN_DTB
>         /* Create two consecutive PMD mappings for FDT early scan */
>         pa = dtb_pa & ~(PMD_SIZE - 1);
>         create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA,
> @@ -506,7 +510,11 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>         create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA + PMD_SIZE,
>                            pa + PMD_SIZE, PMD_SIZE, PAGE_KERNEL);
>         dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE - 1));
> +#else /* CONFIG_BUILTIN_DTB */
> +       dtb_early_va = __va(dtb_pa);
> +#endif /* CONFIG_BUILTIN_DTB */
>  #else
> +#ifndef CONFIG_BUILTIN_DTB
>         /* Create two consecutive PGD mappings for FDT early scan */
>         pa = dtb_pa & ~(PGDIR_SIZE - 1);
>         create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA,
> @@ -514,6 +522,9 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>         create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA + PGDIR_SIZE,
>                            pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
>         dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
> +#else /* CONFIG_BUILTIN_DTB */
> +       dtb_early_va = __va(dtb_pa);
> +#endif /* CONFIG_BUILTIN_DTB */
>  #endif
>         dtb_early_pa = dtb_pa;
>
> --
> 2.20.1
>

Looks good to me.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup