"cache coherency" here means the coherency across cores, not ic/dc
coherency, could you please suggest a suitable name?
Huacai
On Tue, Jan 26, 2016 at 9:42 PM, James Hogan <james.hogan@xxxxxxxxxx> wrote:
> Hi,
>
> On Tue, Jan 26, 2016 at 09:26:23PM +0800, 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.
>
> This is rather ambiguous (the phrase "cache coherency" can be associated
> with dcache coherency between cores). Are you saying that the icache is
> coherent with the dcache, such that writes to dcache are immediately
> visible to instruction fetches on all CPUs in the system without any
> icache flushing?
>
> If so, I think that needs clarifying, e.g. cpu_has_coherent_icache.
>
> Perhaps it should be a flag of icache along with MIPS_CACHE_IC_F_DC too
> which is already intended to avoid the dcache flushes, but not necessary
> the icache flushes.
>
> Cheers
> James
>
>>
>> Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx>
>> ---
>> arch/mips/include/asm/cpu-features.h | 3 +++
>> arch/mips/include/asm/cpu.h | 1 +
>> .../asm/mach-loongson64/cpu-feature-overrides.h | 1 +
>> arch/mips/mm/c-r4k.c | 21 +++++++++++++++++++++
>> 4 files changed, 26 insertions(+)
>>
>> diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
>> index e0ba50a..1ec3dea 100644
>> --- a/arch/mips/include/asm/cpu-features.h
>> +++ b/arch/mips/include/asm/cpu-features.h
>> @@ -148,6 +148,9 @@
>> #ifndef cpu_has_xpa
>> #define cpu_has_xpa (cpu_data[0].options & MIPS_CPU_XPA)
>> #endif
>> +#ifndef cpu_has_coherent_cache
>> +#define cpu_has_coherent_cache (cpu_data[0].options & MIPS_CPU_CACHE_COHERENT)
>> +#endif
>> #ifndef cpu_has_vtag_icache
>> #define cpu_has_vtag_icache (cpu_data[0].icache.flags & MIPS_CACHE_VTAG)
>> #endif
>> diff --git a/arch/mips/include/asm/cpu.h b/arch/mips/include/asm/cpu.h
>> index 5f50551..28471f0 100644
>> --- a/arch/mips/include/asm/cpu.h
>> +++ b/arch/mips/include/asm/cpu.h
>> @@ -391,6 +391,7 @@ enum cpu_type_enum {
>> #define MIPS_CPU_NAN_LEGACY 0x40000000000ull /* Legacy NaN implemented */
>> #define MIPS_CPU_NAN_2008 0x80000000000ull /* 2008 NaN implemented */
>> #define MIPS_CPU_LDPTE 0x100000000000ull /* CPU has ldpte/lddir instructions */
>> +#define MIPS_CPU_CACHE_COHERENT 0x200000000000ull /* CPU maintains cache coherency by hardware */
>>
>> /*
>> * CPU ASE encodings
>> diff --git a/arch/mips/include/asm/mach-loongson64/cpu-feature-overrides.h b/arch/mips/include/asm/mach-loongson64/cpu-feature-overrides.h
>> index c3406db..647d952 100644
>> --- a/arch/mips/include/asm/mach-loongson64/cpu-feature-overrides.h
>> +++ b/arch/mips/include/asm/mach-loongson64/cpu-feature-overrides.h
>> @@ -46,6 +46,7 @@
>> #define cpu_has_local_ebase 0
>>
>> #define cpu_has_wsbh IS_ENABLED(CONFIG_CPU_LOONGSON3)
>> +#define cpu_has_coherent_cache IS_ENABLED(CONFIG_CPU_LOONGSON3)
>> #define cpu_hwrena_impl_bits 0xc0000000
>>
>> #endif /* __ASM_MACH_LOONGSON64_CPU_FEATURE_OVERRIDES_H */
>> diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
>> index 2abc73d..65fb28c 100644
>> --- a/arch/mips/mm/c-r4k.c
>> +++ b/arch/mips/mm/c-r4k.c
>> @@ -429,6 +429,9 @@ static void r4k_blast_scache_setup(void)
>>
>> static inline void local_r4k___flush_cache_all(void * args)
>> {
>> + if (cpu_has_coherent_cache)
>> + return;
>> +
>> switch (current_cpu_type()) {
>> case CPU_LOONGSON2:
>> case CPU_LOONGSON3:
>> @@ -457,6 +460,9 @@ static inline void local_r4k___flush_cache_all(void * args)
>>
>> static void r4k___flush_cache_all(void)
>> {
>> + if (cpu_has_coherent_cache)
>> + return;
>> +
>> r4k_on_each_cpu(local_r4k___flush_cache_all, NULL);
>> }
>>
>> @@ -503,6 +509,9 @@ static void r4k_flush_cache_range(struct vm_area_struct *vma,
>> {
>> int exec = vma->vm_flags & VM_EXEC;
>>
>> + if (cpu_has_coherent_cache)
>> + return;
>> +
>> if (cpu_has_dc_aliases || (exec && !cpu_has_ic_fills_f_dc))
>> r4k_on_each_cpu(local_r4k_flush_cache_range, vma);
>> }
>> @@ -627,6 +636,9 @@ static void r4k_flush_cache_page(struct vm_area_struct *vma,
>> {
>> struct flush_cache_page_args args;
>>
>> + if (cpu_has_coherent_cache)
>> + return;
>> +
>> args.vma = vma;
>> args.addr = addr;
>> args.pfn = pfn;
>> @@ -636,11 +648,17 @@ static void r4k_flush_cache_page(struct vm_area_struct *vma,
>>
>> static inline void local_r4k_flush_data_cache_page(void * addr)
>> {
>> + if (cpu_has_coherent_cache)
>> + return;
>> +
>> r4k_blast_dcache_page((unsigned long) addr);
>> }
>>
>> static void r4k_flush_data_cache_page(unsigned long addr)
>> {
>> + if (cpu_has_coherent_cache)
>> + return;
>> +
>> if (in_atomic())
>> local_r4k_flush_data_cache_page((void *)addr);
>> else
>> @@ -825,6 +843,9 @@ static void local_r4k_flush_cache_sigtramp(void * arg)
>>
>> static void r4k_flush_cache_sigtramp(unsigned long addr)
>> {
>> + if (cpu_has_coherent_cache)
>> + return;
>> +
>> r4k_on_each_cpu(local_r4k_flush_cache_sigtramp, (void *) addr);
>> }
>>
>> --
>> 2.4.6
>>
>>
>>
>>
>>
