[PATCH v2 1/2] powerpc: Introduce POWER10_DD1 feature

[Ravi Bangoria]

On 10/22/20 10:41 AM, Jordan Niethe wrote:
> On Thu, Oct 22, 2020 at 2:40 PM Ravi Bangoria
> <ravi.bangoria at linux.ibm.com> wrote:
>>
>> POWER10_DD1 feature flag will be needed while adding
>> conditional code that applies only for Power10 DD1.
>>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria at linux.ibm.com>
>> ---
>>   arch/powerpc/include/asm/cputable.h | 8 ++++++--
>>   arch/powerpc/kernel/dt_cpu_ftrs.c   | 3 +++
>>   arch/powerpc/kernel/prom.c          | 9 +++++++++
>>   3 files changed, 18 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
>> index 93bc70d4c9a1..d486f56c0d33 100644
>> --- a/arch/powerpc/include/asm/cputable.h
>> +++ b/arch/powerpc/include/asm/cputable.h
>> @@ -216,6 +216,7 @@ static inline void cpu_feature_keys_init(void) { }
>>   #define CPU_FTR_P9_RADIX_PREFETCH_BUG  LONG_ASM_CONST(0x0002000000000000)
>>   #define CPU_FTR_ARCH_31                        LONG_ASM_CONST(0x0004000000000000)
>>   #define CPU_FTR_DAWR1                  LONG_ASM_CONST(0x0008000000000000)
>> +#define CPU_FTR_POWER10_DD1            LONG_ASM_CONST(0x0010000000000000)
>>
>>   #ifndef __ASSEMBLY__
>>
>> @@ -479,6 +480,7 @@ static inline void cpu_feature_keys_init(void) { }
>>              CPU_FTR_DBELL | CPU_FTR_HAS_PPR | CPU_FTR_ARCH_207S | \
>>              CPU_FTR_TM_COMP | CPU_FTR_ARCH_300 | CPU_FTR_ARCH_31 | \
>>              CPU_FTR_DAWR | CPU_FTR_DAWR1)
>> +#define CPU_FTRS_POWER10_DD1   (CPU_FTRS_POWER10 | CPU_FTR_POWER10_DD1)
>>   #define CPU_FTRS_CELL  (CPU_FTR_LWSYNC | \
>>              CPU_FTR_PPCAS_ARCH_V2 | CPU_FTR_CTRL | \
>>              CPU_FTR_ALTIVEC_COMP | CPU_FTR_MMCRA | CPU_FTR_SMT | \
>> @@ -497,14 +499,16 @@ static inline void cpu_feature_keys_init(void) { }
>>   #define CPU_FTRS_POSSIBLE      \
>>              (CPU_FTRS_POWER7 | CPU_FTRS_POWER8E | CPU_FTRS_POWER8 | \
>>               CPU_FTR_ALTIVEC_COMP | CPU_FTR_VSX_COMP | CPU_FTRS_POWER9 | \
>> -            CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10)
>> +            CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10 | \
>> +            CPU_FTRS_POWER10_DD1)
>>   #else
>>   #define CPU_FTRS_POSSIBLE      \
>>              (CPU_FTRS_PPC970 | CPU_FTRS_POWER5 | \
>>               CPU_FTRS_POWER6 | CPU_FTRS_POWER7 | CPU_FTRS_POWER8E | \
>>               CPU_FTRS_POWER8 | CPU_FTRS_CELL | CPU_FTRS_PA6T | \
>>               CPU_FTR_VSX_COMP | CPU_FTR_ALTIVEC_COMP | CPU_FTRS_POWER9 | \
>> -            CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10)
>> +            CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10 | \
>> +            CPU_FTRS_POWER10_DD1)
>>   #endif /* CONFIG_CPU_LITTLE_ENDIAN */
>>   #endif
>>   #else
>> diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
>> index 1098863e17ee..b2327f2967ff 100644
>> --- a/arch/powerpc/kernel/dt_cpu_ftrs.c
>> +++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
>> @@ -811,6 +811,9 @@ static __init void cpufeatures_cpu_quirks(void)
>>          }
>>
>>          update_tlbie_feature_flag(version);
>> +
>> +       if ((version & 0xffffffff) == 0x00800100)
>> +               cur_cpu_spec->cpu_features |= CPU_FTR_POWER10_DD1;
>>   }
>>
>>   static void __init cpufeatures_setup_finished(void)
>> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
>> index c1545f22c077..c778c81284f7 100644
>> --- a/arch/powerpc/kernel/prom.c
>> +++ b/arch/powerpc/kernel/prom.c
>> @@ -305,6 +305,14 @@ static void __init check_cpu_feature_properties(unsigned long node)
>>          }
>>   }
>>
>> +static void __init fixup_cpu_features(void)
>> +{
>> +       unsigned long version = mfspr(SPRN_PVR);
>> +
>> +       if ((version & 0xffffffff) == 0x00800100)
>> +               cur_cpu_spec->cpu_features |= CPU_FTR_POWER10_DD1;
>> +}
>> +
> I am just wondering why this is needed here, but the same thing is not
> done for, say, CPU_FTR_POWER9_DD2_1?

When we don't use DT cpu_features (PowerVM / kvm geusts), we call
identify_cpu() twice. First with Real PVR which sets "raw" cpu_spec
as cur_cpu_spec and then 2nd time with Logical PVR (0x0f...) which
(mostly) overwrites the cur_cpu_spec with "architected" mode cpu_spec.
I don't see DD version specific entries for "architected" mode in
cpu_specs[] for any previous processors. So I've introduced this
function to tweak cpu_features.

Though, I don't know why we don't have similar thing for
CPU_FTR_POWER9_DD2_1. I've to check that.

> And should we get a /* Power10 DD 1 */ added to cpu_specs[]?

IIUC, we don't need such entry. For PowerVM / kvm guests, we overwrite
cpu_spec, so /* Power10 */ "raw" entry is sufficient. And For baremetal,
we don't use cpu_specs[] at all.

> 
>>   static int __init early_init_dt_scan_cpus(unsigned long node,
>>                                            const char *uname, int depth,
>>                                            void *data)
>> @@ -378,6 +386,7 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
>>
>>                  check_cpu_feature_properties(node);
>>                  check_cpu_pa_features(node);
>> +               fixup_cpu_features();
>>          }
>>
>>          identical_pvr_fixup(node);
>> --
>> 2.25.1
>>