From patchwork Tue Aug 13 17:29:40 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sudeep KarkadaNagesha X-Patchwork-Id: 2843915 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 41DDB9F239 for ; Tue, 13 Aug 2013 17:31:51 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 1CC292063B for ; Tue, 13 Aug 2013 17:31:50 +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 AED322063A for ; Tue, 13 Aug 2013 17:31:48 +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 1V9IQz-0002a6-CS; Tue, 13 Aug 2013 17:31:06 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1V9IQh-0006w8-QW; Tue, 13 Aug 2013 17:30:47 +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 1V9IQC-0006qT-88 for linux-arm-kernel@lists.infradead.org; Tue, 13 Aug 2013 17:30:21 +0000 Received: from cam-owa2.Emea.Arm.com (fw-tnat.cambridge.arm.com [217.140.96.21]) by service87.mimecast.com; Tue, 13 Aug 2013 18:29:54 +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); Tue, 13 Aug 2013 18:29:51 +0100 From: Sudeep KarkadaNagesha To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 2/6] drivers: clocksource: configure event stream for ARM arch timer Date: Tue, 13 Aug 2013 18:29:40 +0100 Message-Id: <1376414984-14182-3-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1376414984-14182-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> References: <1374492082-13686-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> <1376414984-14182-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-OriginalArrivalTime: 13 Aug 2013 17:29:51.0767 (UTC) FILETIME=[B7B8DA70:01CE984A] X-MC-Unique: 113081318295402201 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130813_133016_632101_29559509 X-CRM114-Status: GOOD ( 12.70 ) X-Spam-Score: -2.6 (--) Cc: Lorenzo Pieralisi , Mathieu Poirier , 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 only computes the event stream frequency, aiming for a period of 100us between events. ARM/ARM64 specific backends needs to configure and enable the event stream using this frequency. Cc: Mathieu Poirier Cc: Catalin Marinas Reviewed-by: Lorenzo Pieralisi Signed-off-by: Will Deacon [sudeep: moving ARM/ARM64 changes into separate patches, cosmetic changes to commit message] Signed-off-by: Sudeep KarkadaNagesha --- arch/arm/include/asm/arch_timer.h | 2 +- arch/arm64/include/asm/arch_timer.h | 2 +- drivers/clocksource/arm_arch_timer.c | 9 ++++++++- include/clocksource/arm_arch_timer.h | 2 ++ 4 files changed, 12 insertions(+), 3 deletions(-) diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h index 9ef74da..12f3fac 100644 --- a/arch/arm/include/asm/arch_timer.h +++ b/arch/arm/include/asm/arch_timer.h @@ -89,7 +89,7 @@ static inline u64 arch_counter_get_cntvct(void) return cval; } -static inline void arch_counter_set_user_access(void) +static inline void arch_counter_set_user_access(int divider) { u32 cntkctl; diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h index 00b09d0..69f5c8e 100644 --- a/arch/arm64/include/asm/arch_timer.h +++ b/arch/arm64/include/asm/arch_timer.h @@ -97,7 +97,7 @@ static inline u32 arch_timer_get_cntfrq(void) return val; } -static inline void arch_counter_set_user_access(void) +static inline void arch_counter_set_user_access(int divider) { u32 cntkctl; diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index ffadd83..6301ee5 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -125,6 +125,8 @@ static int arch_timer_set_next_event_phys(unsigned long evt, static int arch_timer_setup(struct clock_event_device *clk) { + int evt_stream_div, pos; + clk->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP; clk->name = "arch_sys_timer"; clk->rating = 450; @@ -153,7 +155,12 @@ static int arch_timer_setup(struct clock_event_device *clk) enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI], 0); } - arch_counter_set_user_access(); + /* 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--; + arch_counter_set_user_access(min(pos, 15)); 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);