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cpufreq: intel_pstate: Use passive mode by default without HWP

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After recent changes allowing scale-invariant utilization to be
used on x86, the schedutil governor on top of intel_pstate in the
passive mode should be on par with (or better than) the active mode
"powersave" algorithm of intel_pstate on systems in which
hardware-managed P-states (HWP) are not used, so it should not be
necessary to use the internal scaling algorithm in those cases.

Accordingly, modify intel_pstate to start in the passive mode by
default if the processor at hand does not support HWP of if the driver
is requested to avoid using HWP through the kernel command line.

Among other things, that will allow utilization clamps and the
support for RT/DL tasks in the schedutil governor to be utilized on
systems in which intel_pstate is used.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki
2020-03-25 15:03:35 +01:00
parent 8f3d9f3542
commit 33aa46f252
2 changed files with 21 additions and 14 deletions
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3
drivers/cpufreq/intel_pstate.c
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@@ -2771,6 +2771,8 @@ static int __init intel_pstate_init(void)
pr_info("Invalid MSRs\n");
return -ENODEV;
}
/* Without HWP start in the passive mode. */
default_driver = &intel_cpufreq;
hwp_cpu_matched:
/*
@@ -2816,7 +2818,6 @@ static int __init intel_pstate_setup(char *str)
if (!strcmp(str, "disable")) {
no_load = 1;
} else if (!strcmp(str, "passive")) {
pr_info("Passive mode enabled\n");
default_driver = &intel_cpufreq;
no_hwp = 1;
}