[U-Boot] [PATCH 3/3 v2] ARM: ARM926EJS - Add cache operations

[V, Aneesh]

Hi Eric,

On Mon, Aug 22, 2011 at 7:44 AM, Hong Xu <hong.xu at atmel.com> wrote:
> Hi Aneesh,
>
> On 08/19/2011 10:20 PM, Aneesh V wrote:
>>
>> Hi Hong,
>>
>> On Friday 19 August 2011 02:53 PM, Hong Xu wrote:
>>>
>>> Add a new file arch/arm/cpu/arm926ejs/cache.c and put cache operations
>>> into this file.
>>>
>>> Signed-off-by: Hong Xu<hong.xu at atmel.com>
>>> Tested-by: Elen Song<elen.song at atmel.com>
>>> CC: Albert Aribaud<albert.u.boot at aribaud.net>
>>> ---
>>> Since V1
>>>     Modified copyright line
>>>     Fix for compiling warnings
>>>     Changed the way to use CONFIG_SYS_CACHELINE_SIZE
>>>     When unaligned buffer detected, emit ERROR instead of WARNING
>>>
>>>     Do not make a common v5,v6 cache file. It seems arm946 is lack of
>>>     Test-and-Clean DCache operation. And maybe more differents...
>>>
>>>  arch/arm/cpu/arm926ejs/Makefile |    2 +-
>>>  arch/arm/cpu/arm926ejs/cache.c  |  135
>>> +++++++++++++++++++++++++++++++++++++++
>>>  2 files changed, 136 insertions(+), 1 deletions(-)
>>>  create mode 100644 arch/arm/cpu/arm926ejs/cache.c
>>>
>
> [...]
>
>>> +
>>> +/*
>>> + * The buffer range to be flushed is [start, stop)
>>> + */
>>> +void flush_dcache_range(unsigned long start, unsigned long stop)
>>> +{
>>> +       cache_range_op(start, stop, FLUSH_CACHE_OP);
>>> +}
>>> +
>>> +void flush_dcache_all(void)
>>> +{
>>> +       /*
>>> +        * ARM926EJ-S Technical Reference Manual, Chap 2.3.8
>>> +        * Clean&  Invalidate the entire DCache
>>> +        */
>>> +       asm("0: mrc p15, 0, r15, c7, c14, 3\n\t" "bne 0b\n" : : :
>>> "memory");
>>> +       /* Drain WB */
>>> +       asm("mcr p15, 0, %0, c7, c10, 4\n" : : "r" (0));
>>
>> While looking at the manuals for the armv5 compatibility I stumbled
>> upon the following in Chapter 2.3.8. Are you sure your flush_dcache_all
>> implementation is correct? I suspect the above is flushing only one
>> line?
>>
>> "The test, clean, and invalidate DCache instruction is the same as test
>> and clean DCache,
>> except that when the entire cache has been cleaned, it is invalidated.
>> This means that
>> you can use the following loop to clean and invalidate the entire
>> DCache:
>>
>> tci_loop:     MRC p15, 0, r15, c7, c14, 3
>>               BNE tci_loop
>> "
>
> As stated in the manual, we can use a loop to clean and invalidate the
> entire DCache.
>
> The "asm" statement above is a loop, isn't it? ;-)

Oops! I didn't notice that. Sorry for the noise. But, maybe, it could be made
two separate lines to make it more readable.

br,
Aneesh