linux-kernel - Re: [PATCH v5 04/22] sh: Use P1SEGADDR

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Date:	Sun, 3 Jul 2016 21:48:52 -0400
From:	Rich Felker <dalias@...c.org>
To:	Yoshinori Sato <ysato@...rs.sourceforge.jp>
Cc:	linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 04/22] sh: Use P1SEGADDR

On Mon, Jul 04, 2016 at 01:46:24AM +0900, Yoshinori Sato wrote:
> FDT address is P1SEG. So not virtual address.
> 
> Signed-off-by: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> ---
>  arch/sh/kernel/setup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/sh/kernel/setup.c b/arch/sh/kernel/setup.c
> index 86f2792..8e3b099 100644
> --- a/arch/sh/kernel/setup.c
> +++ b/arch/sh/kernel/setup.c
> @@ -254,7 +254,7 @@ void __ref sh_fdt_init(phys_addr_t dt_phys)
>  #ifdef CONFIG_USE_BUILTIN_DTB
>  	dt_virt = __dtb_start;
>  #else
> -	dt_virt = phys_to_virt(dt_phys);
> +	dt_virt = (void *)P1SEGADDR(dt_phys);
>  #endif
>  
>  	if (!dt_virt || !early_init_dt_scan(dt_virt)) {
> -- 

I don't think this change is correct, and I'm not sure what the
motivation is. It certainly can't work with !CONFIG_29BIT, and likely
can't work on nommu either (it won't work on J2). Maybe we have
different ideas about the sort of physical address the boot loader is
expected to pass; I would expect it to be something that, when passed
to phys_to_virt, yields an address the kernel can use to access the
memory. This does not necessarily mean it's MMU-mapped memory; it
could be (and in practice will be, I think) an address in the P1
segment obtained by adding PAGE_OFFSET (see asm/page.h).

Rich