Re: [loongson-PATCH-v1 22/27] Hibernation Support in mips system

[Hongbing Hu <huhb@lemote.com>]

yanh 写道:
> 在 2009-05-23六的 21:30 +0900，Atsushi Nemoto写道：
>   
>> On Sat, 23 May 2009 16:06:43 +0800, yanh <yanh@lemote.com> wrote:
>>     
>>>>> +unsigned long
>>>>> +	saved_ra,
>>>>> +	saved_sp,
>>>>>           
>> ...
>>     
>>>>> +	saved_v0,
>>>>> +	saved_v1;
>>>>>           
>>>> Instead of enumerating them, I would prefer something like "struct
>>>> pt_regs saved_regs" or "unsigned long saved_regs[32]".
>>>>         
>>> This implementation is referencing the x86 platform. 
>>> Not all the 32 reigsters are needed to save. 
>>> Maybe the whole registers needed to save can still be reduced.
>>>       
>> I did not mean save/restore all registers.  I just mean using only one
>> symbol (struct or array).  Though the struct or array contains some
>> unused members, it saves many instructions in
>> swsusp_arch_{suspend,resume}.
>>
>> For saving N registers, (N * 2) instructions are required to save to
>> individual variables, but (N + 2) instructions are required to save to
>> array or struct.
>>     
>
> Yes, the struct array method is more efficient, we will change to it.
>   
The length of registers  is different between  32bit kernel  and  64bit 
kernel.
That means the file hibernate.S wiil be divided into  hibernate_32.S  
and hibernate_64.S ?

>>>>> +void save_processor_state(void)
>>>>> +{
>>>>> +	saved_status = read_c0_status();
>>>>> +}
>>>>>           
>>>> No need to save/restore floating point registers?
>>>>         
>>> the floating point registers are not used by kernel, for user part, they
>>> are already saved while entering into kernel mode.
>>>       
>> No, floating point registers are not saved on entering into kernel.
>> They are saved on context switch.  
>>     
Yes, suspend to disk  will freeze processes at first,and i think the 
process wiil save the float point regs.
So there is no need to save them.
> It's my mistake. But I think, if there is need to save floating point
> registers, the kernel have already done for it. 
> What's need to save should be for the resuming parts. Those registers which are used while 
> in suspending path are needed to save.
>
> create_image()
>
>    in_suspend = 1;
>     save_processor_state();
>     error = swsusp_arch_suspend();
>     if (error)
>         printk(KERN_ERR "PM: Error %d creating hibernation image\n",
>             error);
>    
>   when resuming this functions is executed for righ after the  swsusp_arch_suspend().
>   This is not a normal function return.
>   So the registers need to save are those damaged by swsusp_arch_suspend and what it calls.
>   
>   because this is not a normal function call, the callee saved registers can not be restored, so we need to save
> it explicitly. For caller saved temporary registers, they are already saved in create_image.  Are this right?
>       
>   
---
>> Atsushi Nemoto
>>     
>
>
>
>   


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