Messages in this thread | | | Subject | Re: [PATCH] cpufreq: intel_pstate: Load when ACPI PCCH is present | From | Srinivas Pandruvada <> | Date | Tue, 17 Jul 2018 10:23:00 -0700 |
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On Tue, 2018-07-17 at 18:13 +0200, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Currently, intel_pstate doesn't load if _PSS is not present on > HP Proliant systems, because it expects the firmware to take over > CPU performance scaling in that case. However, if ACPI PCCH is > present, the firmware expects the kernel to use it for CPU > performance scaling and the pcc-cpufreq driver is loaded for that. > > Unfortunately, the firmware interface used by that driver is not > scalable for fundamental reasons, so pcc-cpufreq is way suboptimal > on systems with more than just a few CPUs. In fact, it is better to > avoid using it at all. > > For this reason, modify intel_pstate to look for ACPI PCCH if _PSS > is not present and load if it is there. > > Fixes: fbbcdc0744da (intel_pstate: skip the driver if ACPI has power > mgmt option) > Reported-by: Andreas Herrmann <aherrmann@suse.com> > Tested-by: Andreas Herrmann <aherrmann@suse.com> > Reviewed-by: Andreas Herrmann <aherrmann@suse.com> > Cc: 4.17+ <stable@vger.kernel.org> # 4.17+ > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
But do we need a change as done by the following commit in in pcc- cpufreq.c?
" commit 8a61e12e84597b5f8155ac91b44dea866ccfaac2 Author: Yinghai Lu <yinghai@kernel.org> Date: Fri Sep 20 10:43:56 2013 -0700
acpi-cpufreq: skip loading acpi_cpufreq after intel_pstate
"
Thanks, Srinivas
> --- > drivers/cpufreq/intel_pstate.c | 17 ++++++++++++++++- > 1 file changed, 16 insertions(+), 1 deletion(-) > > Index: linux-pm/drivers/cpufreq/intel_pstate.c > =================================================================== > --- linux-pm.orig/drivers/cpufreq/intel_pstate.c > +++ linux-pm/drivers/cpufreq/intel_pstate.c > @@ -2391,6 +2391,18 @@ static bool __init intel_pstate_no_acpi_ > return true; > } > > +static bool __init intel_pstate_no_acpi_pcch(void) > +{ > + acpi_status status; > + acpi_handle handle; > + > + status = acpi_get_handle(NULL, "\\_SB", &handle); > + if (ACPI_FAILURE(status)) > + return true; > + > + return !acpi_has_method(handle, "PCCH"); > +} > + > static bool __init intel_pstate_has_acpi_ppc(void) > { > int i; > @@ -2450,7 +2462,10 @@ static bool __init intel_pstate_platform > > switch (plat_info[idx].data) { > case PSS: > - return intel_pstate_no_acpi_pss(); > + if (!intel_pstate_no_acpi_pss()) > + return false; > + > + return intel_pstate_no_acpi_pcch(); > case PPC: > return intel_pstate_has_acpi_ppc() && !force_load; > } >
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