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From:   Anup Patel <anup@brainfault.org>
Date:   Fri, 15 Jan 2021 15:09:21 +0530
Message-ID: <CAAhSdy04Nm+ET3Oepe5zRyVWiWpZzmfe=0BrdOEPUHGEOF86Vw@mail.gmail.com>
Subject: Re: [PATCH] RISC-V: simplify BUILTIN_DTB processing
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>,
        Palmer Dabbelt <palmerdabbelt@google.com>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        devicetree@vger.kernel.org
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On Tue, Jan 12, 2021 at 2:51 AM Vitaly Wool <vitaly.wool@konsulko.com> wrote:
>
> Provide __dtb_start as a parameter to setup_vm() in case
> CONFIG_BUILTIN_DTB is true, so we don't have to duplicate
> BUILTIN_DTB specific processing in MMU-enabled and MMU-disabled
> versions of setup_vm().
>
> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
> ---
>  arch/riscv/kernel/head.S | 4 ++++
>  arch/riscv/mm/init.c     | 4 ----
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 16e9941900c4..f5a9bad86e58 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -260,7 +260,11 @@ clear_bss_done:
>
>         /* Initialize page tables and relocate to virtual addresses */
>         la sp, init_thread_union + THREAD_SIZE
> +#ifdef CONFIG_BUILTIN_DTB
> +       la a0, __dtb_start
> +#else
>         mv a0, s1
> +#endif /* CONFIG_BUILTIN_DTB */
>         call setup_vm
>  #ifdef CONFIG_MMU
>         la a0, early_pg_dir
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 5b17f8d22f91..45faad7c4291 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -615,11 +615,7 @@ static void __init setup_vm_final(void)
>  #else
>  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>  {
> -#ifdef CONFIG_BUILTIN_DTB
> -       dtb_early_va = (void *) __dtb_start;
> -#else
>         dtb_early_va = (void *)dtb_pa;
> -#endif
>         dtb_early_pa = dtb_pa;
>  }
>
> --
> 2.20.1
>

We can avoid the early DTB mapping for MMU-enabled case when
BUILTIN_DTB is enabled (same as previous discussion). Otherwise
looks good to me.

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

Regards,
Anup