Hi, Steven,
Maybe you are misunderstand Loongson-3's "hardware-maintained cache".
Loongson-3's hardware maintain the cache coherency between multi-cores
(also maintain coherency between CPU-core and DMA), but Loongson-3 can
*still* has cache alias (Cache alias in Loongson is sovled by 16K
PageSize).
Meanwhile, I know why you misunderstand, because my code is like this:
static inline void local_r4k___flush_cache_all(void * args)
if (cpu_has_coherent_cache)
return;
This implies that Loongson-3 has no cache alias, but in fact this is wrong
if Loongson has configured PageSize < 16K.
I think I should make my code in all flush functions like this:
static inline void local_r4k___flush_cache_all(void * args)
if (cpu_has_coherent_cache && !cpu_has_dc_aliases)
return;
Am I right?
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 01/30/2013 12:24 AM, Huacai Chen wrote:
>> Loongson-3 maintains cache coherency by hardware. So we introduce a cpu
>> feature named cpu_has_coherent_cache and use it to modify MIPS's cache
>> flushing functions.
>>
>> Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx> Signed-off-by: Hongliang
>> Tao
>> <taohl@xxxxxxxxxx> Signed-off-by: Hua Yan <yanh@xxxxxxxxxx> ---
>> arch/mips/include/asm/cacheflush.h | 6 +++++
>> arch/mips/include/asm/cpu-features.h | 3 ++
>> .../asm/mach-loongson/cpu-feature-overrides.h | 6 +++++
>> arch/mips/mm/c-r4k.c | 21
>> ++++++++++++++++++- 4 files changed, 34 insertions(+), 2 deletions(-)
>>
> Hello.
>
> This patch masks the problem that you are not properly probing your L1
> caches
> to start with. For some reason in 'probe_pcache()' you reach the default
> case
> where the primary data cache is marked as having aliases. If your CPU
> truly is
> HW coherent with no aliases, then MIPS_CACHE_ALIASES should never get set.
> Fixing this would eliminate the 'arch/mips/include/asm/cacheflush.h' and
> 'arch/mips/mm/c-r4k.c' changes completely. There is no need to add more
> CPU
> feature bits for this single platform, thus changes to 'cpu-features.h'
> and
> 'cpu-features-overrides.h' will not be accepted.
>
> Also, please do not copy the <linux-kernel@xxxxxxxxxxxxxxx> mailing list
> unless your patch touches files outside of 'arch/mips' in order to cut
> down
> traffic on an already busy list. Thanks.
>
> Steve
> - -----
> <sjhill@xxxxxxxx>
> <Steven.Hill@xxxxxxxxxx>
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