linux-kernel - Re: [PATCH 1/1] ARM: pxa168: fix corrected reset vector

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Message-ID: <AANLkTinjyJvMRt8OovZBJD+-xU6KXH5WAfqz9Epok+=g@mail.gmail.com>
Date:	Tue, 31 Aug 2010 14:26:34 +0800
From:	Haojian Zhuang <haojian.zhuang@...il.com>
To:	Eric Miao <eric.y.miao@...il.com>
Cc:	"Mark F. Brown" <mark.brown314@...il.com>,
	Haojian Zhuang <haojian.zhuang@...vell.com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] ARM: pxa168: fix corrected reset vector

On Tue, Aug 31, 2010 at 2:08 PM, Eric Miao <eric.y.miao@...il.com> wrote:
> On Tue, Aug 31, 2010 at 2:04 PM, Eric Miao <eric.y.miao@...il.com> wrote:
>> On Tue, Aug 31, 2010 at 2:02 PM, Mark F. Brown <mark.brown314@...il.com> wrote:
>>> On Tue, Aug 31, 2010 at 1:48 AM, Eric Miao <eric.y.miao@...il.com> wrote:
>>>> On Thu, Aug 26, 2010 at 5:07 PM, Mark F. Brown <mark.brown314@...il.com> wrote:
>>>>> Signed-off-by: Mark F. Brown <mark.brown314@...il.com>
>>>>> ---
>>>>>  arch/arm/mach-mmp/include/mach/system.h |    2 +-
>>>>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>>>>
>>>>> diff --git a/arch/arm/mach-mmp/include/mach/system.h b/arch/arm/mach-mmp/include/mach/system.h
>>>>> index 4f5b0e0..926e9c0 100644
>>>>> --- a/arch/arm/mach-mmp/include/mach/system.h
>>>>> +++ b/arch/arm/mach-mmp/include/mach/system.h
>>>>> @@ -16,6 +16,6 @@ static inline void arch_idle(void)
>>>>>
>>>>>  static inline void arch_reset(char mode, const char *cmd)
>>>>>  {
>>>>> -       cpu_reset(0);
>>>>> +       cpu_reset(0xffff0000);
>>>>
>>>> Not sure if this correct. But normally reset jump happens after we turn
>>>> off the MMU and so on. Ain't the BootROM starts from 0 ?
>>>>
>>>>>  }
>>>>>  #endif /* __ASM_MACH_SYSTEM_H */
>>>>> --
>>>>> 1.7.0.4
>>>>>
>>>>>
>>>>
>>>
>>> Eric, the boot-rom for pxa168 starts at 0xffff_0000. I am pretty sure
>>> about that! If you set the reset vector to 0x0 it will crash during
>>> reboot. I will send you xdb snapshots if you need me to.
>>>
>>
>> OK, you are expert on this :-)
>>
>> Applied to 'fix'.
>>
>
> One moment. Since this is really global to pxa910 and mmp2, so I
> suggest this being fixed for pxa168 only first. How about this:
>
>    ARM: pxa168: fix corrected reset vector
>
>    Reset vector for pxa168 is 0xffff_0000 not 0x0. This fix allows
>    reboot to work
>
>    Signed-off-by: Mark F. Brown <mark.brown314@...il.com>
>
> diff --git a/arch/arm/mach-mmp/include/mach/system.h
> b/arch/arm/mach-mmp/include/mach/system.h
> index 4f5b0e0..1a8a25e 100644
> --- a/arch/arm/mach-mmp/include/mach/system.h
> +++ b/arch/arm/mach-mmp/include/mach/system.h
> @@ -9,6 +9,8 @@
>  #ifndef __ASM_MACH_SYSTEM_H
>  #define __ASM_MACH_SYSTEM_H
>
> +#include <mach/cputype.h>
> +
>  static inline void arch_idle(void)
>  {
>        cpu_do_idle();
> @@ -16,6 +18,9 @@ static inline void arch_idle(void)
>
>  static inline void arch_reset(char mode, const char *cmd)
>  {
> -       cpu_reset(0);
> +       if (cpu_is_pxa168())
> +               cpu_reset(0xffff0000);
> +       else
> +               cpu_reset(0);
>  }
>  #endif /* __ASM_MACH_SYSTEM_H */
> --
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>
The reset code is in below.

	.align	5
ENTRY(cpu_mohawk_reset)
	mov	ip, #0
	mcr	p15, 0, ip, c7, c7, 0		@ invalidate I,D caches
	mcr	p15, 0, ip, c7, c10, 4		@ drain WB
	mcr	p15, 0, ip, c8, c7, 0		@ invalidate I & D TLBs
	mrc	p15, 0, ip, c1, c0, 0		@ ctrl register
	bic	ip, ip, #0x0007			@ .............cam
	bic	ip, ip, #0x1100			@ ...i...s........
	mcr	p15, 0, ip, c1, c0, 0		@ ctrl register
	mov	pc, r0

MMU is disabled at here and replace PC with r0 value. I doubt code
executed correctly at here. While MMU is disabled, the PC should be
continue in the range of 0xCxxx_xxxx (kernel space). "mov pc, r0"
shouldn't be executed. Instruction fetch failure should occurs since
there's no physical address in 0xCxxx_xxxx.

Correct me if I'm wrong.

Thanks
Haojian
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