From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Wang Subject: [PATCH v3] Optimize C3 entry on Centaur CPUs Date: Tue, 29 May 2018 18:12:37 +0800 Message-ID: <1527588757-19229-1-git-send-email-davidwang@zhaoxin.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Sender: linux-kernel-owner@vger.kernel.org To: rjw@rjwysocki.net, mingo@redhat.com, len.brown@intel.com, pavel@ucw.cz, tglx@linutronix.de, hpa@zytor.com, x86@kernel.org, linux-pm@kernel.org, linux-kernel@vger.kernel.org Cc: brucechang@via-alliance.com, cooperyan@zhaoxin.com, qiyuanwang@zhaoxin.com, benjaminpan@viatech.com, lukelin@viacpu.com, timguo@zhaoxin.com, David Wang List-Id: linux-pm@vger.kernel.org For new Centaur CPUs the ucode will take care of the preservation of cache coherence between CPU cores in C-states regardless of how deep the C-states are. So, it is not necessary to flush the caches in software befor entering C3. Signed-off-by: David Wang Changes from v2 to v3: *1, Replace "c->x86_mask" with "c->x86_stepping". Changes from v1 to v2: * 1, Add some Family/Model/Stepping contrains to let this patch only apply * to new centaur CPUs. * 2, The arbiter disable/enable operations maybe needed for old VIA/Centaur * platform. So, delete "flags->bm_control=0" in patch v1. --- arch/x86/kernel/acpi/cstate.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c index dde437f..a82fed6 100644 --- a/arch/x86/kernel/acpi/cstate.c +++ b/arch/x86/kernel/acpi/cstate.c @@ -51,6 +51,19 @@ void acpi_processor_power_init_bm_check(struct acpi_processor_flags *flags, if (c->x86_vendor == X86_VENDOR_INTEL && (c->x86 > 0xf || (c->x86 == 6 && c->x86_model >= 0x0f))) flags->bm_control = 0; + + /* + * For all recent Centaur CPUs, the ucode will make sure that each + * core can keep cache coherence with each other while entering C3 + * type state. So, set bm_check to 1 to indicate that the kernel + * need not execute a cache flush operation (WBINVD) when entering + * C3 type state. + */ + if (c->x86_vendor == X86_VENDOR_CENTAUR) { + if (c->x86 > 6 || (c->x86 == 6 && c->x86_model == 0x0f && + c->x86_stepping >= 0x0e)) + flags->bm_check = 1; + } } EXPORT_SYMBOL(acpi_processor_power_init_bm_check); -- 1.9.1