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

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Date:	Wed, 06 Jul 2016 23:11:44 +0900
From:	Yoshinori Sato <ysato@...rs.sourceforge.jp>
To:	Rich Felker <dalias@...c.org>
Cc:	linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 04/22] sh: Use P1SEGADDR

On Mon, 04 Jul 2016 10:48:52 +0900,
Rich Felker wrote:
> 
> 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

Hmm...
It's better to pass a virtual address in bootloader.

-- 
Yoshinori Sato
<ysato@...rs.sourceforge.jp>