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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Nov 05, 2020 at 12:27:02PM +0000, Ionela Voinescu wrote: > If Activity Monitors (AMUs) are present, two of the counters can be used > to implement support for CPPC's (Collaborative Processor Performance > Control) delivered and reference performance monitoring functionality > using FFH (Functional Fixed Hardware). > > Given that counters for a certain CPU can only be read from that CPU, > while FFH operations can be called from any CPU for any of the CPUs, use > smp_call_function_single() to provide the requested values. > > Therefore, depending on the register addresses, the following values > are returned: > - 0x0 (DeliveredPerformanceCounterRegister): AMU core counter > - 0x1 (ReferencePerformanceCounterRegister): AMU constant counter > > The use of Activity Monitors is hidden behind the generic > {read,store}_{corecnt,constcnt}() functions. > > Read functionality for these two registers represents the only current > FFH support for CPPC. Read operations for other register values or write > operation for all registers are unsupported. Therefore, keep CPPC's FFH > unsupported if no CPUs have valid AMU frequency counters. For this > purpose, the get_cpu_with_amu_feat() is introduced. > > Signed-off-by: Ionela Voinescu > Cc: Catalin Marinas > Cc: Will Deacon > --- > arch/arm64/include/asm/cpufeature.h | 3 ++ > arch/arm64/kernel/cpufeature.c | 10 ++++++ > arch/arm64/kernel/topology.c | 54 +++++++++++++++++++++++++++++ > 3 files changed, 67 insertions(+) > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index 751bd9d3376b..f5b44ac354dc 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -772,6 +772,9 @@ static inline bool cpu_has_amu_feat(int cpu) > } > #endif > > +/* Get a cpu that supports the Activity Monitors Unit (AMU) */ > +extern int get_cpu_with_amu_feat(void); > + > static inline unsigned int get_vmid_bits(u64 mmfr1) > { > int vmid_bits; > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 1142970e985b..6b08ae74ad0a 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -1526,6 +1526,11 @@ bool cpu_has_amu_feat(int cpu) > return cpumask_test_cpu(cpu, &amu_cpus); > } > > +int get_cpu_with_amu_feat(void) > +{ > + return cpumask_any(&amu_cpus); > +} > + > static void cpu_amu_enable(struct arm64_cpu_capabilities const *cap) > { > if (has_cpuid_feature(cap, SCOPE_LOCAL_CPU)) { > @@ -1554,6 +1559,11 @@ static bool has_amu(const struct arm64_cpu_capabilities *cap, > > return true; > } > +#else > +int get_cpu_with_amu_feat(void) > +{ > + return nr_cpu_ids; > +} > #endif > > #ifdef CONFIG_ARM64_VHE > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > index 764fdb0f947b..7d25087deaa5 100644 > --- a/arch/arm64/kernel/topology.c > +++ b/arch/arm64/kernel/topology.c > @@ -154,6 +154,9 @@ void update_freq_counters_refs(void) > > static inline bool freq_counters_valid(int cpu) > { > + if ((cpu >= nr_cpu_ids) || !cpumask_test_cpu(cpu, cpu_present_mask)) > + return false; > + > if (!cpu_has_amu_feat(cpu)) { > pr_debug("CPU%d: counters are not supported.\n", cpu); > return false; > @@ -330,3 +333,54 @@ void topology_scale_freq_tick(void) > this_cpu_write(arch_core_cycles_prev, core_cnt); > this_cpu_write(arch_const_cycles_prev, const_cnt); > } > + > +#ifdef CONFIG_ACPI_CPPC_LIB > +#include As mentioned on patch 1, I think it'd be better to open-code the smp call functions here, e.g. static void cpu_read_corecnt(void *val) { *(u64 *)val = read_corecnt() } static void cpu_read_constcnt(void *val) { *(u64 *)val = read_constcnt() } ... as they're only needed here and it's much clearer what they're doing in-context. I think that would als oget rid of the warning you mention in the cover letter. Thanks, Mark. > + > +static inline > +int counters_read_on_cpu(int cpu, smp_call_func_t func, u64 *val) > +{ > + if (!cpu_has_amu_feat(cpu)) > + return -EOPNOTSUPP; > + > + smp_call_function_single(cpu, func, val, 1); > + > + return 0; > +} > + > +/* > + * Refer to drivers/acpi/cppc_acpi.c for the description of the functions > + * below. > + */ > +bool cpc_ffh_supported(void) > +{ > + return freq_counters_valid(get_cpu_with_amu_feat()); > +} > + > +int cpc_read_ffh(int cpu, struct cpc_reg *reg, u64 *val) > +{ > + int ret = -EOPNOTSUPP; > + > + switch ((u64)reg->address) { > + case 0x0: > + ret = counters_read_on_cpu(cpu, store_corecnt, val); > + break; > + case 0x1: > + ret = counters_read_on_cpu(cpu, store_constcnt, val); > + break; > + } > + > + if (!ret) { > + *val &= GENMASK_ULL(reg->bit_offset + reg->bit_width - 1, > + reg->bit_offset); > + *val >>= reg->bit_offset; > + } > + > + return ret; > +} > + > +int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val) > +{ > + return -EOPNOTSUPP; > +} > +#endif /* CONFIG_ACPI_CPPC_LIB */ > -- > 2.17.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel