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

[Haojian Zhuang]

On Tue, Aug 31, 2010 at 3:08 PM, Eric Miao <eric.y.miao@xxxxxxxxx> wrote:
> On Tue, Aug 31, 2010 at 3:02 PM, Haojian Zhuang
> <haojian.zhuang@xxxxxxxxx> wrote:
>> On Tue, Aug 31, 2010 at 2:48 PM, Mark F. Brown <mark.brown314@xxxxxxxxx> wrote:
>>> On Tue, Aug 31, 2010 at 2:26 AM, Haojian Zhuang
>>> <haojian.zhuang@xxxxxxxxx> wrote:
>>>> On Tue, Aug 31, 2010 at 2:08 PM, Eric Miao <eric.y.miao@xxxxxxxxx> wrote:
>>>>> On Tue, Aug 31, 2010 at 2:04 PM, Eric Miao <eric.y.miao@xxxxxxxxx> wrote:
>>>>>> On Tue, Aug 31, 2010 at 2:02 PM, Mark F. Brown <mark.brown314@xxxxxxxxx> wrote:
>>>>>>> On Tue, Aug 31, 2010 at 1:48 AM, Eric Miao <eric.y.miao@xxxxxxxxx> wrote:
>>>>>>>> On Thu, Aug 26, 2010 at 5:07 PM, Mark F. Brown <mark.brown314@xxxxxxxxx> wrote:
>>>>>>>>> Signed-off-by: Mark F. Brown <mark.brown314@xxxxxxxxx>
>>>>>>>>> ---
>>>>>>>>>  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@xxxxxxxxx>
>>>>>
>>>>> 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
>>>>
>>>
>>> Haojian,
>>>
>>> I think there is a pipeline execution of the mov pc, r0 instruction.
>>> If I remember correctly you need to do a similar jump when you turn
>>> the MMU on in early boot code. If it makes any difference I did test
>>> this code on pxa168 before submitting it. I will double check the mmp2
>>> and the pxa910 reset vectors with the Boot ROM developers.
>>>
>>
>> In early boot code, 1:1 (physical:virtual) mapping is used. It means
>> that physical address is same as virtual address. So you can operature
>> mmu as you wish.
>>
>> By the way, I don't suggest to reset CPU by this way. Reset is not
>> only make code running from the head, it should also clear registers
>> and RTL logic in CPU.
>>
>
> Depends on if pxa168 has a reset signal asserted from internal or from
> external GPIO, which is controllable from the CPU itself. That's what
> pxa is doing at this moment.
>

Yes, it depends on reset signal. Watchdog timer is built in pxa168. So
I think that watchdog reset could be better.
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