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

[Eric Miao]

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>
>>>>>>>> ---
>>>>>>>> Âarch/arm/mach-mmp/include/mach/system.h | Â Â2 +-
>>>>>>>> Â1 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)
>>>>>>>>
>>>>>>>> Âstatic inline void arch_reset(char mode, const char *cmd)
>>>>>>>> Â{
>>>>>>>> - Â Â Â cpu_reset(0);
>>>>>>>> + Â Â Â 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 ?
>>>>>>>
>>>>>>>> Â}
>>>>>>>> Â#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:
>>>>
>>>> Â ÂARM: pxa168: fix corrected reset vector
>>>>
>>>> Â ÂReset vector for pxa168 is 0xffff_0000 not 0x0. This fix allows
>>>> Â Âreboot to work
>>>>
>>>> Â ÂSigned-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 @@
>>>> Â#ifndef __ASM_MACH_SYSTEM_H
>>>> Â#define __ASM_MACH_SYSTEM_H
>>>>
>>>> +#include <mach/cputype.h>
>>>> +
>>>> Âstatic inline void arch_idle(void)
>>>> Â{
>>>> Â Â Â Âcpu_do_idle();
>>>> @@ -16,6 +18,9 @@ static inline void arch_idle(void)
>>>>
>>>> Âstatic inline void arch_reset(char mode, const char *cmd)
>>>> Â{
>>>> - Â Â Â cpu_reset(0);
>>>> + Â Â Â if (cpu_is_pxa168())
>>>> + Â Â Â Â Â Â Â cpu_reset(0xffff0000);
>>>> + Â Â Â else
>>>> + Â Â Â Â Â Â Â cpu_reset(0);
>>>> Â}
>>>> Â#endif /* __ASM_MACH_SYSTEM_H */
>>>> --
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>>>>
>>> The reset code is in below.
>>>
>>> Â Â Â Â.align Â5
>>> ENTRY(cpu_mohawk_reset)
>>>    Âmov   ip, #0
>>>    Âmcr   p15, 0, ip, c7, c7, 0      @ invalidate I,D caches
>>>    Âmcr   p15, 0, ip, c7, c10, 4     Â@ drain WB
>>>    Âmcr   p15, 0, ip, c8, c7, 0      @ invalidate I & D TLBs
>>>    Âmrc   p15, 0, ip, c1, c0, 0      @ ctrl register
>>>    Âbic   ip, ip, #0x0007         @ .............cam
>>>    Âbic   ip, ip, #0x1100         @ ...i...s........
>>>    Âmcr   p15, 0, ip, c1, c0, 0      @ ctrl register
>>>    Âmov   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.
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