The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 95d6c0857e54b788982746071130d822a795026b Mon Sep 17 00:00:00 2001

From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com Date: Wed, 18 Jul 2018 13:38:37 +0200 Subject: [PATCH] cpufreq: intel_pstate: Register when ACPI PCCH is present

Currently, intel_pstate doesn't register 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 register if it is there. Also prevent the pcc-cpufreq driver from trying to initialize itself if intel_pstate has been registered already.

Fixes: fbbcdc0744da (intel_pstate: skip the driver if ACPI has power mgmt option) Reported-by: Andreas Herrmann aherrmann@suse.com Reviewed-by: Andreas Herrmann aherrmann@suse.com Acked-by: Srinivas Pandruvada srinivas.pandruvada@linux.intel.com Tested-by: Andreas Herrmann aherrmann@suse.com Cc: 4.16+ stable@vger.kernel.org # 4.16+ Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index ece120da3353..3c3971256130 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -2394,6 +2394,18 @@ static bool __init intel_pstate_no_acpi_pss(void) 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; @@ -2453,7 +2465,10 @@ static bool __init intel_pstate_platform_pwr_mgmt_exists(void)

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; } diff --git a/drivers/cpufreq/pcc-cpufreq.c b/drivers/cpufreq/pcc-cpufreq.c index 3f0ce2ae35ee..0c56c9759672 100644 --- a/drivers/cpufreq/pcc-cpufreq.c +++ b/drivers/cpufreq/pcc-cpufreq.c @@ -580,6 +580,10 @@ static int __init pcc_cpufreq_init(void) { int ret;

+ /* Skip initialization if another cpufreq driver is there. */ + if (cpufreq_get_current_driver()) + return 0; + if (acpi_disabled) return 0;