Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Tue, 17 Jul 2018 19:28:41 +0200 | Subject | Re: [PATCH] cpufreq: intel_pstate: Load when ACPI PCCH is present |
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On Tue, Jul 17, 2018 at 7:23 PM, Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> wrote: > 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 > > "
Quite likely yes, good point!
>> --- >> 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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