The CPPC driver reads delivered and reference counters using cpc_read one at a time. This leads to inaccurate measurement of CPU frequency discussed in [1]. If the firmware indicates that both the registers are in the FFH interface the kernel can read the registers together in a single IPI. This has two benefits: 1. Reduces the number of IPIs needed to read the two registers 2. The two registers will be read in close proximity resulting in more accurate CPU frequency measurement [1]: https://lore.kernel.org/all/20230328193846.8757-1-yang@xxxxxxxxxxxxxxxxxxxxxx/ Signed-off-by: Vanshidhar Konda <vanshikonda@xxxxxxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/topology.c | 37 ++++++++++++++++++++++++++++++++++++ drivers/acpi/cppc_acpi.c | 32 +++++++++++++++++++++++++++---- include/acpi/cppc_acpi.h | 13 +++++++++++++ 3 files changed, 78 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index 8905eb0c681f..8207565f43ee 100644 --- a/arch/arm64/kernel/topology.c +++ b/arch/arm64/kernel/topology.c @@ -421,6 +421,43 @@ int cpc_read_ffh(int cpu, struct cpc_reg *reg, u64 *val) return ret; } +static void cpc_update_freq_counters(void *info) +{ + update_freq_counters_refs(); +} + +int cpc_read_regs_ffh(int cpu, struct ffh_cpc_reg_values *ffh_regs) +{ + struct amu_counters *ctrs = per_cpu_ptr(&cpu_samples, cpu); + int idx; + + if (!cpc_ffh_supported() || !freq_counters_valid(cpu)) + return -EOPNOTSUPP; + + if (WARN_ON_ONCE(irqs_disabled())) + return -EPERM; + + if (!idle_cpu(cpu)) + smp_call_function_single(cpu, cpc_update_freq_counters, NULL, 1); + + for (idx = 0; idx < MAX_NUM_CPC_REGS_FFH; idx++) { + + if (!ffh_regs->regs[idx].reg) + continue; + + switch ((u64)(ffh_regs->regs[idx].reg->address)) { + case 0x0: + ffh_regs->regs[idx].value = ctrs->core_cnt; + break; + case 0x1: + ffh_regs->regs[idx].value = ctrs->const_cnt; + break; + } + } + + return 0; +} + int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val) { return -EOPNOTSUPP; diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index d155a86a8614..55ffb1915e4f 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -113,6 +113,10 @@ static DEFINE_PER_CPU(struct cpc_desc *, cpc_desc_ptr); (cpc)->cpc_entry.reg.space_id == \ ACPI_ADR_SPACE_SYSTEM_IO) +#define CPC_IN_FFH(cpc) ((cpc)->type == ACPI_TYPE_BUFFER && \ + (cpc)->cpc_entry.reg.space_id == \ + ACPI_ADR_SPACE_FIXED_HARDWARE) + /* Evaluates to True if reg is a NULL register descriptor */ #define IS_NULL_REG(reg) ((reg)->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY && \ (reg)->address == 0 && \ @@ -974,6 +978,11 @@ int __weak cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val) return -ENOTSUPP; } +int __weak cpc_read_regs_ffh(int cpu, struct ffh_cpc_reg_values *regs) +{ + return -ENOTSUPP; +} + /* * Since cpc_read and cpc_write are called while holding pcc_lock, it should be * as fast as possible. We have already mapped the PCC subspace during init, so @@ -1317,7 +1326,7 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs) int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum); struct cppc_pcc_data *pcc_ss_data = NULL; u64 delivered, reference, ref_perf, ctr_wrap_time; - int ret = 0, regs_in_pcc = 0; + int ret = 0, regs_in_pcc = 0, regs_read_in_ffh = 0; if (!cpc_desc) { pr_debug("No CPC descriptor for CPU:%d\n", cpunum); @@ -1353,8 +1362,23 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs) } } - cpc_read(cpunum, delivered_reg, &delivered); - cpc_read(cpunum, reference_reg, &reference); + if (CPC_IN_FFH(delivered_reg) && CPC_IN_FFH(reference_reg)) { + struct ffh_cpc_reg_values ffh_regs; + + ffh_regs.regs[0].reg = &(delivered_reg->cpc_entry.reg); + ffh_regs.regs[1].reg = &(reference_reg->cpc_entry.reg); + ret = cpc_read_regs_ffh(cpunum, &ffh_regs); + if (!ret) { + delivered = ffh_regs.regs[0].value; + reference = ffh_regs.regs[1].value; + regs_read_in_ffh = 1; + } + } + + if (!regs_read_in_ffh) { + cpc_read(cpunum, delivered_reg, &delivered); + cpc_read(cpunum, reference_reg, &reference); + } cpc_read(cpunum, ref_perf_reg, &ref_perf); /* @@ -1366,7 +1390,7 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs) if (CPC_SUPPORTED(ctr_wrap_reg)) cpc_read(cpunum, ctr_wrap_reg, &ctr_wrap_time); - if (!delivered || !reference || !ref_perf) { + if (!delivered || !reference || !ref_perf) { ret = -EFAULT; goto out_err; } diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h index 3a0995f8bce8..0da614a50edd 100644 --- a/include/acpi/cppc_acpi.h +++ b/include/acpi/cppc_acpi.h @@ -137,6 +137,18 @@ struct cppc_cpudata { }; #ifdef CONFIG_ACPI_CPPC_LIB + +#define MAX_NUM_CPC_REGS_FFH 2 + +struct ffh_cpc_reg { + struct cpc_reg *reg; + u64 value; +}; + +struct ffh_cpc_reg_values { + struct ffh_cpc_reg regs[MAX_NUM_CPC_REGS_FFH]; +}; + extern int cppc_get_desired_perf(int cpunum, u64 *desired_perf); extern int cppc_get_nominal_perf(int cpunum, u64 *nominal_perf); extern int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs); @@ -153,6 +165,7 @@ extern unsigned int cppc_get_transition_latency(int cpu); extern bool cpc_ffh_supported(void); extern bool cpc_supported_by_cpu(void); extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val); +extern int cpc_read_regs_ffh(int cpu, struct ffh_cpc_reg_values *regs); extern int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val); extern int cppc_get_epp_perf(int cpunum, u64 *epp_perf); extern int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable); -- 2.43.1
