Messages in this thread | | | Subject | Re: [PATCH v4 05/10] powerpc/dt_cpu_ftrs: Add feature for 2nd DAWR | From | Ravi Bangoria <> | Date | Tue, 21 Jul 2020 19:46:55 +0530 |
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On 7/21/20 7:37 PM, Michael Ellerman wrote: > Ravi Bangoria <ravi.bangoria@linux.ibm.com> writes: >> On 7/21/20 4:59 PM, Michael Ellerman wrote: >>> Ravi Bangoria <ravi.bangoria@linux.ibm.com> writes: >>>> On 7/17/20 11:14 AM, Jordan Niethe wrote: >>>>> On Fri, Jul 17, 2020 at 2:10 PM Ravi Bangoria >>>>> <ravi.bangoria@linux.ibm.com> wrote: >>>>>> >>>>>> Add new device-tree feature for 2nd DAWR. If this feature is present, >>>>>> 2nd DAWR is supported, otherwise not. >>>>>> >>>>>> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com> >>>>>> --- >>>>>> arch/powerpc/include/asm/cputable.h | 7 +++++-- >>>>>> arch/powerpc/kernel/dt_cpu_ftrs.c | 7 +++++++ >>>>>> 2 files changed, 12 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h >>>>>> index e506d429b1af..3445c86e1f6f 100644 >>>>>> --- a/arch/powerpc/include/asm/cputable.h >>>>>> +++ b/arch/powerpc/include/asm/cputable.h >>>>>> @@ -214,6 +214,7 @@ static inline void cpu_feature_keys_init(void) { } >>>>>> #define CPU_FTR_P9_TLBIE_ERAT_BUG LONG_ASM_CONST(0x0001000000000000) >>>>>> #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) >>>>>> >>>>>> #ifndef __ASSEMBLY__ >>>>>> >>>>>> @@ -497,14 +498,16 @@ 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_FTR_DAWR1) >>>>>> #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_FTR_DAWR1) >>> >>>>> Instead of putting CPU_FTR_DAWR1 into CPU_FTRS_POSSIBLE should it go >>>>> into CPU_FTRS_POWER10? >>>>> Then it will be picked up by CPU_FTRS_POSSIBLE. >>>> >>>> I remember a discussion about this with Mikey and we decided to do it >>>> this way. Obviously, the purpose is to make CPU_FTR_DAWR1 independent of >>>> CPU_FTRS_POWER10 because DAWR1 is an optional feature in p10. I fear >>>> including CPU_FTR_DAWR1 in CPU_FTRS_POWER10 can make it forcefully enabled >>>> even when device-tree property is not present or pa-feature bit it not set, >>>> because we do: >>>> >>>> { /* 3.1-compliant processor, i.e. Power10 "architected" mode */ >>>> .pvr_mask = 0xffffffff, >>>> .pvr_value = 0x0f000006, >>>> .cpu_name = "POWER10 (architected)", >>>> .cpu_features = CPU_FTRS_POWER10, >>> >>> The pa-features logic will turn it off if the feature bit is not set. >>> >>> So you should be able to put it in CPU_FTRS_POWER10. >>> >>> See for example CPU_FTR_NOEXECUTE. >> >> Ah ok. scan_features() clears the feature if the bit is not set in >> pa-features. So it should work find for powervm. I'll verify the same >> thing happens in case of baremetal where we use cpu-features not >> pa-features. If it works in baremetal as well, will put it in >> CPU_FTRS_POWER10. > > When we use DT CPU features we don't use CPU_FTRS_POWER10 at all. > > We construct a cpu_spec from scratch with just the base set of features: > > static struct cpu_spec __initdata base_cpu_spec = { > .cpu_name = NULL, > .cpu_features = CPU_FTRS_DT_CPU_BASE, > > > And then individual features are enabled via the device tree flags.
Ah good. I was under a wrong impression that we use cpu_specs[] for all the cases. Thanks mpe for explaining in detail :)
Ravi
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