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

[Albert ARIBAUD]

Le 12/01/2011 05:31, Lei Wen a écrit :
> On Wed, Jan 12, 2011 at 12:27 PM, Lei Wen<adrian.wenl at gmail.com>  wrote:
>> 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.
>
> I take my words back...
> I forget to open the dcache... After dcache is on, the usb tftp still
> cannot works...
> Seems still do the clean cache operation...

Anyway, changes to ARM926E-JS common code must work with existing 
ARM926E-JS SoCs, so this patch is NAK. Pantheon-specific cache ops 
should only be executed for Pantheon-based boards.

> Best regards,
> Lei

Amicalement,
-- 
Albert.