Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759011Ab3HMR37 (ORCPT ); Tue, 13 Aug 2013 13:29:59 -0400 Received: from service87.mimecast.com ([91.220.42.44]:45617 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758961Ab3HMR3z (ORCPT ); Tue, 13 Aug 2013 13:29:55 -0400 From: Sudeep KarkadaNagesha To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Sudeep.KarkadaNagesha@arm.com, Lorenzo Pieralisi , Catalin Marinas , Will Deacon , Thomas Gleixner , Daniel Lezcano , Mathieu Poirier , Sudeep KarkadaNagesha 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 Content-Type: text/plain; charset=WINDOWS-1252 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id r7DHWBvi000837 Content-Length: 3828 Lines: 105 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); -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/