From patchwork Fri Aug 23 16:19:08 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sudeep KarkadaNagesha X-Patchwork-Id: 2848936 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 713A9BF546 for ; Fri, 23 Aug 2013 16:23:27 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8581120480 for ; Fri, 23 Aug 2013 16:23:26 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 71ED52047B for ; Fri, 23 Aug 2013 16:23:25 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1VCu7k-0005is-9N; Fri, 23 Aug 2013 16:22:09 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1VCu7P-0007vo-Od; Fri, 23 Aug 2013 16:21:47 +0000 Received: from service87.mimecast.com ([91.220.42.44]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1VCu6R-0007p2-FZ for linux-arm-kernel@lists.infradead.org; Fri, 23 Aug 2013 16:20:53 +0000 Received: from cam-owa2.Emea.Arm.com (fw-tnat.cambridge.arm.com [217.140.96.21]) by service87.mimecast.com; Fri, 23 Aug 2013 17:20:26 +0100 Received: from e103737-lin.cambridge.arm.com ([10.1.255.212]) by cam-owa2.Emea.Arm.com with Microsoft SMTPSVC(6.0.3790.3959); Fri, 23 Aug 2013 17:20:23 +0100 From: Sudeep KarkadaNagesha To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 4/5] drivers: clocksource: add support for ARM architected timer event stream Date: Fri, 23 Aug 2013 17:19:08 +0100 Message-Id: <1377274749-6196-5-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1377274749-6196-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> References: <1377274749-6196-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-OriginalArrivalTime: 23 Aug 2013 16:20:23.0626 (UTC) FILETIME=[AB7282A0:01CEA01C] X-MC-Unique: 113082317202603201 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130823_122047_744637_578B700A X-CRM114-Status: GOOD ( 15.18 ) X-Spam-Score: -2.6 (--) Cc: Lorenzo Pieralisi , Sudeep KarkadaNagesha , Catalin Marinas , Daniel Lezcano , Will Deacon , Thomas Gleixner X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-7.0 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Will Deacon The ARM architected timer can generate events (used for waking up CPUs executing the wfe instruction) at a frequency represented as a power-of-2 divisor of the clock rate. An event stream might be used: - To impose a time-out on a wfe polling loop. - To safeguard against any programming error in case an expected event is not generated. - To implement wfe-based timeouts for userspace locking implementations. This patch computes the event stream frequency aiming for a period of 100us between events. It uses ARM/ARM64 specific backends to configure and enable the event stream. Cc: Catalin Marinas Cc: Lorenzo Pieralisi Signed-off-by: Will Deacon [sudeep: moving ARM/ARM64 changes into separate patches and adding Kconfig option] Signed-off-by: Sudeep KarkadaNagesha --- drivers/clocksource/Kconfig | 14 ++++++++++++++ drivers/clocksource/arm_arch_timer.c | 23 +++++++++++++++++++++++ include/clocksource/arm_arch_timer.h | 2 ++ 3 files changed, 39 insertions(+) diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig index b7b9b04..8c10d9a 100644 --- a/drivers/clocksource/Kconfig +++ b/drivers/clocksource/Kconfig @@ -74,6 +74,20 @@ config ARM_ARCH_TIMER bool select CLKSRC_OF if OF +config ARM_ARCH_TIMER_EVTSTREAM + bool "Support for ARM architected timer event stream generation" + default y if ARM_ARCH_TIMER + help + This option enables support for event stream generation based on + the ARM architected timer. It is used for waking up CPUs executing + the wfe instruction at a frequency represented as a power-of-2 + divisor of the clock rate. An event stream might be useful for + imposing timeout on a wfe, safeguarding against any programming + errors in case an expected event is not generated or even to + implement wfe-based timeouts for userspace locking implementations. + This can be disabled for hardware validation purposes to detect any + hardware anamolies of missing events. + config ARM_GLOBAL_TIMER bool select CLKSRC_OF if OF diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index ffadd83..e331818 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -123,6 +123,28 @@ static int arch_timer_set_next_event_phys(unsigned long evt, return 0; } +#ifdef CONFIG_ARM_ARCH_TIMER_EVTSTREAM +static void arch_timer_setup_evtstream(void) +{ + int evt_stream_div, pos; + + /* Find the closest power of two to the divisor */ + evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ; + pos = fls(evt_stream_div); + if (pos > 1 && !(evt_stream_div & (1 << (pos - 2)))) + pos--; + /* enable event stream */ + arch_timer_evtstrm_config(true, min(pos, 15)); + /* enable hwcap definition to the users for event stream feature */ + arch_timer_set_hwcap_evtstrm(); +} +#else +static void arch_timer_setup_evtstream(void) +{ + arch_timer_evtstrm_config(false, 0); +} +#endif + static int arch_timer_setup(struct clock_event_device *clk) { clk->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP; @@ -154,6 +176,7 @@ static int arch_timer_setup(struct clock_event_device *clk) } arch_counter_set_user_access(); + arch_timer_setup_evtstream(); return 0; } diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h index 551f7e9..c4d0fc4 100644 --- a/include/clocksource/arm_arch_timer.h +++ b/include/clocksource/arm_arch_timer.h @@ -37,6 +37,8 @@ #define ARCH_TIMER_USR_VT_ACCESS_EN (1 << 8) /* virtual timer registers */ #define ARCH_TIMER_USR_PT_ACCESS_EN (1 << 9) /* physical timer registers */ +#define ARCH_TIMER_EVT_STREAM_FREQ 10000 /* 100us */ + #ifdef CONFIG_ARM_ARCH_TIMER extern u32 arch_timer_get_rate(void);