[U-Boot] [U-BOOT] [PATCH] arm: fix flush cache function on arm926ejs

[Lei Wen]

Hi Albert,

On Wed, Jan 12, 2011 at 3:53 AM, Albert ARIBAUD <albert.aribaud at free.fr> wrote:
> Hi,
>
> Le 11/01/2011 16:40, Lei Wen a écrit :
>> flush_cache function should only be called when the dcache is on.
>> And original flush method for arm926ejs seems don't work, replace
>> it with new version.
>>
>> Test on Marvell Pantheon pxa920 board with usb ether function.
>>
>> Signed-off-by: Lei Wen<leiwen at marvell.com>
>> ---
>>   arch/arm/lib/cache.c |    8 ++++----
>>   1 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/lib/cache.c b/arch/arm/lib/cache.c
>> index 30686fe..b8d5eee 100644
>> --- a/arch/arm/lib/cache.c
>> +++ b/arch/arm/lib/cache.c
>> @@ -27,16 +27,16 @@
>>
>>   void  flush_cache (unsigned long dummy1, unsigned long dummy2)
>>   {
>> +     if (!dcache_status())
>> +             return;
>>   #if defined(CONFIG_OMAP2420) || defined(CONFIG_ARM1136)
>>       void arm1136_cache_flush(void);
>>
>>       arm1136_cache_flush();
>>   #endif
>>   #ifdef CONFIG_ARM926EJS
>> -     /* test and clean, page 2-23 of arm926ejs manual */
>> -     asm("0: mrc p15, 0, r15, c7, c10, 3\n\t" "bne 0b\n" : : : "memory");
>> -     /* disable write buffer as well (page 2-22) */
>> -     asm("mcr p15, 0, %0, c7, c10, 4" : : "r" (0));
>> +     /* clean&  invalidate all D cache */
>> +     asm("mcr p15, 0, %0, c7, c14, 0" : : "r" (0));
>
> ARM's ARM926EJ-S r0p4/r0p5 TRM does not define "... c7, c14, 0". Where
> did you find this exact cp15 instruction?
>

My mistake...
Pantheon board's sheeva core modify the standard cp15 op code a bit...
With one opcode, it could invalidate and clean the dcache all.

So could I modify the original patch like below?
asm("mcr p15, 0, %0, c7, c6, 0" : : "r" (0));
This would only invalidate all dcache. Since current dcache enable is
just write-through,
I think it is safe to just do the invalidate operation.

This also could works for my board.

Best regards,
Lei