[ECOS] Problem found with flash driver

["Retallack, Mark" <mark.retallack@siemens.com>]

Hello everyone, I think I have found a minor problem with the io layer
of the flash driver and before I continue with my fix, I just thought
that I would ask if anyone else has seen it. 

I am using JFFS2 over a flash bank that I am not running code from, so
interrupts can be enabled during flash access. The processor is an
MPC850. 

With the virgin eCos flash.c code (from CVS), the system crashes with a
random memory corruption, I have tracked it down to a context switch
within the flash_program function in flash.c. After looking through the
file and the eCos mailing list I found that the HAL_FLASH_CACHES_OFF
define states that interrupts must be disabled. 

After modding the code to disable interrupts before flushing and
disabling the cache, the system works correctly with no problems.  

I have not created a patch because the HAL_FLASH_CACHES_OFF define in
flash.h looks very generic and I cannot test the mod. But this is what I
have done:

// Note: the ucache code has not been tested yet on any target.
#define HAL_FLASH_CACHES_OFF(_d_, _i_)          \
    CYG_MACRO_START                             \
    _i_ = 0; /* avoids warning */               \
    unsigned long __state;                      \
    HAL_DISABLE_INTERRUPTS(__state);            \    
    HAL_UCACHE_IS_ENABLED(_d_);                 \
    HAL_UCACHE_SYNC();                          \
    HAL_UCACHE_INVALIDATE_ALL();                \
    HAL_UCACHE_DISABLE();                       \
    HAL_RESTORE_INTERRUPTS(__state);            \    
    CYG_MACRO_END

#define HAL_FLASH_CACHES_ON(_d_, _i_)           \
    CYG_MACRO_START                             \
    unsigned long __state;                      \
    HAL_DISABLE_INTERRUPTS(__state);            \    
    if (_d_) HAL_UCACHE_ENABLE();               \
    HAL_RESTORE_INTERRUPTS(__state);            \    
    CYG_MACRO_END

#else  // HAL_CACHE_UNIFIED

#define HAL_FLASH_CACHES_OFF(_d_, _i_)          \
    CYG_MACRO_START                             \
    _i_ = 0; /* avoids warning */               \
    unsigned long __state;                      \
    HAL_DISABLE_INTERRUPTS(__state);            \
    HAL_DCACHE_IS_ENABLED(_d_);                 \
    HAL_DCACHE_SYNC();                          \
    HAL_DCACHE_INVALIDATE_ALL();                \
    HAL_DCACHE_DISABLE();                       \
    HAL_ICACHE_INVALIDATE_ALL();                \
    HAL_RESTORE_INTERRUPTS(__state);            \
    CYG_MACRO_END

#define HAL_FLASH_CACHES_ON(_d_, _i_)           \
    CYG_MACRO_START                             \
    unsigned long __state;                      \
    HAL_DISABLE_INTERRUPTS(__state);            \
    if (_d_) HAL_DCACHE_ENABLE();               \
    HAL_RESTORE_INTERRUPTS(__state);            \
    CYG_MACRO_END

I know that someone else has already pointed out this potential problem,
but no fix was added, this makes me worry because I cannot be the only
persion who is using the jffs2 system on a powerpc 850, and this is a
very easy problem to reproduce.



Mark Retallack
Embedded Software Engineer
Siemens Traffic Controls 
Sopers Lane, Poole, Dorset. BH17 7ER. UK.
Tel: 01202 782189
Fax: 01202 782545
www.siemenstraffic.com

Committed to quality traffic solutions and service excellence


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