From: Rafael J. Wysocki <[email protected]> There may be reasons to use generic cpufreq governors (eg. schedutil) on Intel platforms instead of the intel_pstate driver's internal governor. However, that currently can only be done by disabling intel_pstate altogether and using the acpi-cpufreq driver instead of it, which is subject to limitations.
First of all, acpi-cpufreq only works on systems where the _PSS object is present in the ACPI tables for all logical CPUs. Second, on those systems acpi-cpufreq will only use frequencies listed by _PSS which may be suboptimal. In particular, by convention, the whole turbo range is represented in _PSS as a single P-state and the frequency assigned to it is greater by 1 MHz than the greatest non-turbo frequency listed by _PSS. That may confuse governors to use turbo frequencies less frequently which may lead to suboptimal performance. For this reason, make it possible to use the intel_pstate driver with generic cpufreq governors as a "normal" cpufreq driver. That mode is enforced by adding intel_pstate=passive to the kernel command line and cannot be disabled at run time. In that mode, intel_pstate provides a cpufreq driver interface including the ->target() and ->fast_switch() callbacks and is listed in scaling_driver as "intel_cpufreq". Signed-off-by: Rafael J. Wysocki <[email protected]> --- Rebased on top of my linux-next branch, which in turn is based on 4.9-rc5 now. I'm running this on my IVB laptop w/ the schedutil governor, no problems so far (fingers crossed). Thanks, Rafael --- Documentation/kernel-parameters.txt | 6 + drivers/cpufreq/intel_pstate.c | 169 ++++++++++++++++++++++++++++++------ 2 files changed, 151 insertions(+), 24 deletions(-) Index: linux-pm/drivers/cpufreq/intel_pstate.c =================================================================== --- linux-pm.orig/drivers/cpufreq/intel_pstate.c +++ linux-pm/drivers/cpufreq/intel_pstate.c @@ -37,6 +37,8 @@ #include <asm/cpufeature.h> #include <asm/intel-family.h> +#define INTEL_CPUFREQ_TRANSITION_LATENCY 20000 + #define ATOM_RATIOS 0x66a #define ATOM_VIDS 0x66b #define ATOM_TURBO_RATIOS 0x66c @@ -122,6 +124,8 @@ struct sample { * @scaling: Scaling factor to convert frequency to cpufreq * frequency units * @turbo_pstate: Max Turbo P state possible for this platform + * @max_freq: @max_pstate frequency in cpufreq units + * @turbo_freq: @turbo_pstate frequency in cpufreq units * * Stores the per cpu model P state limits and current P state. */ @@ -132,6 +136,8 @@ struct pstate_data { int max_pstate_physical; int scaling; int turbo_pstate; + unsigned int max_freq; + unsigned int turbo_freq; }; /** @@ -470,7 +476,7 @@ static void intel_pstate_init_acpi_perf_ { } -static void intel_pstate_exit_perf_limits(struct cpufreq_policy *policy) +static inline int intel_pstate_exit_perf_limits(struct cpufreq_policy *policy) { } #endif @@ -1225,6 +1231,8 @@ static void intel_pstate_get_cpu_pstates cpu->pstate.max_pstate_physical = pstate_funcs.get_max_physical(); cpu->pstate.turbo_pstate = pstate_funcs.get_turbo(); cpu->pstate.scaling = pstate_funcs.get_scaling(); + cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling; + cpu->pstate.turbo_freq = cpu->pstate.turbo_pstate * cpu->pstate.scaling; if (pstate_funcs.get_vid) pstate_funcs.get_vid(cpu); @@ -1367,8 +1375,6 @@ static inline void intel_pstate_update_p { int max_perf, min_perf; - update_turbo_state(); - intel_pstate_get_min_max(cpu, &min_perf, &max_perf); pstate = clamp_t(int, pstate, min_perf, max_perf); trace_cpu_frequency(pstate * cpu->pstate.scaling, cpu->cpu); @@ -1389,6 +1395,8 @@ static inline void intel_pstate_adjust_b target_pstate = cpu->policy == CPUFREQ_POLICY_PERFORMANCE ? cpu->pstate.turbo_pstate : pstate_funcs.get_target_pstate(cpu); + update_turbo_state(); + intel_pstate_update_pstate(cpu, target_pstate); sample = &cpu->sample; @@ -1670,22 +1678,21 @@ static int intel_pstate_verify_policy(st return 0; } -static void intel_pstate_stop_cpu(struct cpufreq_policy *policy) +static void intel_cpufreq_stop_cpu(struct cpufreq_policy *policy) { - int cpu_num = policy->cpu; - struct cpudata *cpu = all_cpu_data[cpu_num]; - - pr_debug("CPU %d exiting\n", cpu_num); - - intel_pstate_clear_update_util_hook(cpu_num); + intel_pstate_set_min_pstate(all_cpu_data[policy->cpu]); +} - if (hwp_active) - return; +static void intel_pstate_stop_cpu(struct cpufreq_policy *policy) +{ + pr_debug("CPU %d exiting\n", policy->cpu); - intel_pstate_set_min_pstate(cpu); + intel_pstate_clear_update_util_hook(policy->cpu); + if (!hwp_active) + intel_cpufreq_stop_cpu(policy); } -static int intel_pstate_cpu_init(struct cpufreq_policy *policy) +static int intel_cpufreq_cpu_init(struct cpufreq_policy *policy) { struct cpudata *cpu; int rc; @@ -1696,11 +1703,6 @@ static int intel_pstate_cpu_init(struct cpu = all_cpu_data[policy->cpu]; - if (limits->min_perf_pct == 100 && limits->max_perf_pct == 100) - policy->policy = CPUFREQ_POLICY_PERFORMANCE; - else - policy->policy = CPUFREQ_POLICY_POWERSAVE; - /* * We need sane value in the cpu->perf_limits, so inherit from global * perf_limits limits, which are seeded with values based on the @@ -1720,9 +1722,11 @@ static int intel_pstate_cpu_init(struct policy->cpuinfo.max_freq *= cpu->pstate.scaling; intel_pstate_init_acpi_perf_limits(policy); - policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL; + policy->cpuinfo.transition_latency = INTEL_CPUFREQ_TRANSITION_LATENCY; cpumask_set_cpu(policy->cpu, policy->cpus); + policy->fast_switch_possible = true; + return 0; } @@ -1730,10 +1734,27 @@ static int intel_pstate_cpu_exit(struct { intel_pstate_exit_perf_limits(policy); + policy->fast_switch_possible = false; + return 0; } -static struct cpufreq_driver intel_pstate_driver = { +static int intel_pstate_cpu_init(struct cpufreq_policy *policy) +{ + int ret = intel_cpufreq_cpu_init(policy); + + if (ret) + return ret; + + if (limits->min_perf_pct == 100 && limits->max_perf_pct == 100) + policy->policy = CPUFREQ_POLICY_PERFORMANCE; + else + policy->policy = CPUFREQ_POLICY_POWERSAVE; + + return 0; +} + +static struct cpufreq_driver intel_pstate = { .flags = CPUFREQ_CONST_LOOPS, .verify = intel_pstate_verify_policy, .setpolicy = intel_pstate_set_policy, @@ -1745,6 +1766,99 @@ static struct cpufreq_driver intel_pstat .name = "intel_pstate", }; +static int intel_cpufreq_verify_policy(struct cpufreq_policy *policy) +{ + struct cpudata *cpu = all_cpu_data[policy->cpu]; + struct perf_limits *perf_limits = limits; + + update_turbo_state(); + policy->cpuinfo.max_freq = limits->turbo_disabled ? + cpu->pstate.max_freq : cpu->pstate.turbo_freq; + + cpufreq_verify_within_cpu_limits(policy); + + if (per_cpu_limits) + perf_limits = cpu->perf_limits; + + intel_pstate_update_perf_limits(policy, perf_limits); + + return 0; +} + +static unsigned int intel_cpufreq_turbo_update(struct cpudata *cpu, + struct cpufreq_policy *policy, + unsigned int target_freq) +{ + unsigned int max_freq; + + update_turbo_state(); + + max_freq = limits->no_turbo || limits->turbo_disabled ? + cpu->pstate.max_freq : cpu->pstate.turbo_freq; + policy->cpuinfo.max_freq = max_freq; + if (policy->max > max_freq) + policy->max = max_freq; + + if (target_freq > max_freq) + target_freq = max_freq; + + return target_freq; +} + +static int intel_cpufreq_target(struct cpufreq_policy *policy, + unsigned int target_freq, + unsigned int relation) +{ + struct cpudata *cpu = all_cpu_data[policy->cpu]; + struct cpufreq_freqs freqs; + int target_pstate; + + freqs.old = policy->cur; + freqs.new = intel_cpufreq_turbo_update(cpu, policy, target_freq); + + cpufreq_freq_transition_begin(policy, &freqs); + switch (relation) { + case CPUFREQ_RELATION_L: + target_pstate = DIV_ROUND_UP(freqs.new, cpu->pstate.scaling); + break; + case CPUFREQ_RELATION_H: + target_pstate = freqs.new / cpu->pstate.scaling; + break; + default: + target_pstate = DIV_ROUND_CLOSEST(freqs.new, cpu->pstate.scaling); + break; + } + intel_pstate_update_pstate(cpu, target_pstate); + cpufreq_freq_transition_end(policy, &freqs, false); + + return 0; +} + +static unsigned int intel_cpufreq_fast_switch(struct cpufreq_policy *policy, + unsigned int target_freq) +{ + struct cpudata *cpu = all_cpu_data[policy->cpu]; + int target_pstate; + + target_freq = intel_cpufreq_turbo_update(cpu, policy, target_freq); + target_pstate = DIV_ROUND_UP(target_freq, cpu->pstate.scaling); + intel_pstate_update_pstate(cpu, target_pstate); + return target_freq; +} + +static struct cpufreq_driver intel_cpufreq = { + .flags = CPUFREQ_CONST_LOOPS, + .verify = intel_cpufreq_verify_policy, + .target = intel_cpufreq_target, + .fast_switch = intel_cpufreq_fast_switch, + .init = intel_cpufreq_cpu_init, + .exit = intel_pstate_cpu_exit, + .stop_cpu = intel_cpufreq_stop_cpu, + .name = "intel_cpufreq", +}; + +static struct cpufreq_driver *intel_pstate_driver = &intel_pstate; + static int no_load __initdata; static int no_hwp __initdata; static int hwp_only __initdata; @@ -1963,7 +2077,7 @@ hwp_cpu_matched: if (!hwp_active && hwp_only) goto out; - rc = cpufreq_register_driver(&intel_pstate_driver); + rc = cpufreq_register_driver(intel_pstate_driver); if (rc) goto out; @@ -1978,7 +2092,9 @@ out: get_online_cpus(); for_each_online_cpu(cpu) { if (all_cpu_data[cpu]) { - intel_pstate_clear_update_util_hook(cpu); + if (intel_pstate_driver == &intel_pstate) + intel_pstate_clear_update_util_hook(cpu); + kfree(all_cpu_data[cpu]); } } @@ -1994,8 +2110,13 @@ static int __init intel_pstate_setup(cha if (!str) return -EINVAL; - if (!strcmp(str, "disable")) + if (!strcmp(str, "disable")) { no_load = 1; + } else if (!strcmp(str, "passive")) { + pr_info("Passive mode enabled\n"); + intel_pstate_driver = &intel_cpufreq; + no_hwp = 1; + } if (!strcmp(str, "no_hwp")) { pr_info("HWP disabled\n"); no_hwp = 1; Index: linux-pm/Documentation/kernel-parameters.txt =================================================================== --- linux-pm.orig/Documentation/kernel-parameters.txt +++ linux-pm/Documentation/kernel-parameters.txt @@ -1760,6 +1760,12 @@ bytes respectively. Such letter suffixes disable Do not enable intel_pstate as the default scaling driver for the supported processors + passive + Use intel_pstate as a scaling driver, but configure it + to work with generic cpufreq governors (instead of + enabling its internal governor). This mode cannot be + used along with the hardware-managed P-states (HWP) + feature. force Enable intel_pstate on systems that prohibit it by default in favor of acpi-cpufreq. Forcing the intel_pstate driver
