[U-Boot] [PATCH] imx: don't clobber reset cause

[Stefano Babic]

Hi Eric,

On 05/02/2015 18:22, Eric Nelson wrote:

>>> There is very similar code in 'arch/arm/cpu/armv7/vf610/generic.c'.  The
>>> write is for a hard power on case where these reason registers are full
>>> of weird bogus values (at least on Vybrid; I suspect on iMx).  In the
>>> case of a non-POR, the register bits are good.  However, if you don't
>>> clear the status, on the next reset it may have multiple registers bits
>>> even though you really want to know the last reason (bit).
>>>
>>> Another option would be to clear the value and store the 'cause'
>>> somewhere for other U-Boot users.  Unless you wanted to read this from
>>> an OS?  I think both files should behave the same, all else equal.
>>>
>>
>> I have assumed (maybe wrong ?) that the reason for the patch is to let
>> the OS reading these bits.
>>
> 
> In some cases (Windows Embedded), yes.
> 
> In the Linux case, we'll likely pass the value to the kernel through
> the kernel command-line, so it's available to userspace.
> 
> I'm not aware of any kernel functionality for this at the moment.
> 

It remains the issue raised by Bill (thanks for that). If the bits are
not reset, we can determine the cause only after POR, but not anymore
after a warm start. Can you maybe use the IRAM to pass the information
to Windows ?

Best regards,
Stefano Babic


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