On 2012?05?31? 11:58, Catalin Marinas wrote:

On 31 May 2012 11:38, bill4carson[off-list ref]  wrote:

quoted

On 2012?05?31? 11:19, Catalin Marinas wrote:

quoted

BTW, see this as a starting point (and a hack):

http://article.gmane.org/gmane.linux.ports.arm.kernel/51556

I think we has some mis-understanding here :(

As for:v6_flush_kern_dcache_area/v6_flush_kern_dcache_all
these two hooks is supposed to be globally effective, *not*
locally!

Hence, there should below fix to make it as globally effective.


+#ifdef CONFIG_SMP
+       ldr     r2, [r0]                        @ read for ownership
+       str     r2, [r0]                        @ write for ownership
+#endif /* CONFIG_SMP */

Or there maybe some other better solution for this issue.

I still didn't fully understand what the problem is. So, to make sure,
if you run some applications from flash using a yaffs filesystem, you
get random crashes. Is this correct? If yes, a solution is to actually
call flush_dcache_page() on the CPU that does the page copying from
flash into RAM, which could be the yaffs filesystem.

The story goes like this:
function "flush_dcache_page" should be global effective
but in ARMv6 MPCore, it was not, it was just local effective due
to hardware design. This may cause error in some cases for example:

1) Task running on Core-0 loading text section into memory.
    It was preempted and then migrate into Core-1;
2) On Core-1, this task continue loading it and then
    "flush_dcache_page" to make sure the loaded text section write
    into main memory.
3) Task tend to the loaded text section and running it.

If the "flush_dcache_page" was not global effective,
there maybe data still in Core-0's data cache, not write
into main memory. Thus in step 3, error instruction maybe
fetched thus cause strange error.

If I'm missing something here, please let me know.

thanks

-- 
Love each day!

--bill