[uClinux-dev] cache fault in coldfire 5282 design

[Greg Ungerer]

Hi Bernd,

Bernd Büttner wrote:
> I'm porting uCLinux to our own design with Coldfire 5282 CPU and 
> NAND-FLASH.
> I'm using 20070130 distibution.
> In 'CACHE_ENABLE' are SDRAM and (internal)FLASH defined as cacheable and 
> all other areas as non-cacheable.
> FLASH is defined for a fixed address, but I think every design will have 
> it on another address.

Yes, this looks like a bad idea. It should only cache RAM
(as it does for every other CPU type in there).


> I think this should be done with config parameters. But that is not my 
> problem.
> In the macro '__flush_cache_all' for the 5282 not in the ACR registers 
> defined memory areas
> are defined (unlike CACHE_ENABLE) as cacheable and write-buffered.
> Therefore my NAND-FLASH is cacheable with write-buffered access!

Yep, they are not consistent between the 2 settings.


> The result is, when the for-loop in 'nand_write_buf' in nand_base.c is 
> interrupted (timer-interrupt),
> sometimes the write to the nand-port is doubled and the data in 
> nand-flash is corrupted.
> The code in '__flush_cache_all' should be:
> 
> --- cacheflush.h.org    2007-03-22 13:15:12.000000000 +0100
> +++ cacheflush.h    2007-10-25 16:12:25.000000000 +0200
> @@ -52,7 +52,7 @@
>  #endif /* CONFIG_M5407 */
>  #if defined(CONFIG_M527x) || defined(CONFIG_M528x)
>      __asm__ __volatile__ (
> -            "movel    #0x81400100, %%d0\n\t"
> +            "movel    #0x81000200, %%d0\n\t"
>              "movec    %%d0, %%CACR\n\t"
>          "nop\n\t"
>          : : : "d0" );
> 
> A #define used in 'CACHE_ENABLE' and '__flush_cache_all' could avoid the 
> difference.
> The second thing is that a function called 'flush_cache_all' should 
> flush the complete cache
> and not only the instruction cache. For this 'flush_icache' is defined.

Yes, it should be flushing everything. The cache code is less
than ideal for most ColdFire members. It needs a good cleanup.

Regards
Greg



------------------------------------------------------------------------
Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg at snapgear.com
Secure Computing Corporation                PHONE:       +61 7 3435 2888
825 Stanley St,                             FAX:         +61 7 3891 3630
Woolloongabba, QLD, 4102, Australia         WEB: http://www.SnapGear.com