Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932606Ab3GVLV7 (ORCPT ); Mon, 22 Jul 2013 07:21:59 -0400 Received: from service87.mimecast.com ([91.220.42.44]:42526 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932380Ab3GVLVc (ORCPT ); Mon, 22 Jul 2013 07:21:32 -0400 From: Sudeep KarkadaNagesha To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Sudeep.KarkadaNagesha@arm.com, Mark Rutland , Lorenzo Pieralisi , Russell King , Catalin Marinas , Will Deacon , Mathieu Poirier Subject: [PATCH v2 1/3] drivers: clocksource: configure event stream for ARM arch timer Date: Mon, 22 Jul 2013 12:21:20 +0100 Message-Id: <1374492082-13686-2-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1374492082-13686-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> References: <1371575223-21702-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> <1374492082-13686-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-OriginalArrivalTime: 22 Jul 2013 11:21:28.0481 (UTC) FILETIME=[9C0C9110:01CE86CD] X-MC-Unique: 113072212213002701 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 r6MBM4QX009574 Content-Length: 3992 Lines: 115 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. This patch configures the event stream, aiming for a period of 100us between events. This can be used to implement wfe-based timeouts for userspace locking implementations. Cc: Mathieu Poirier Reviewed-by: Lorenzo Pieralisi Signed-off-by: Will Deacon --- arch/arm/include/asm/arch_timer.h | 5 +++-- arch/arm64/include/asm/arch_timer.h | 6 +++--- drivers/clocksource/arm_arch_timer.c | 9 ++++++++- include/clocksource/arm_arch_timer.h | 2 ++ 4 files changed, 16 insertions(+), 6 deletions(-) diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h index e406d57..c3d9ef7 100644 --- a/arch/arm/include/asm/arch_timer.h +++ b/arch/arm/include/asm/arch_timer.h @@ -89,14 +89,15 @@ 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; asm volatile("mrc p15, 0, %0, c14, c1, 0" : "=r" (cntkctl)); /* disable user access to everything */ - cntkctl &= ~((3 << 8) | (7 << 0)); + cntkctl &= ~((3 << 8) | (0xf << 4) | (3 << 0)); + cntkctl |= (divider << 4) | (1 << 2); asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl)); } diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h index 98abd47..8c1e42f 100644 --- a/arch/arm64/include/asm/arch_timer.h +++ b/arch/arm64/include/asm/arch_timer.h @@ -97,16 +97,16 @@ 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; /* Disable user access to the timers and the physical counter. */ asm volatile("mrs %0, cntkctl_el1" : "=r" (cntkctl)); - cntkctl &= ~((3 << 8) | (1 << 0)); + cntkctl &= ~((3 << 8) | (0xf << 4) | (1 << 0)); /* Enable user access to the virtual counter and frequency. */ - cntkctl |= (1 << 1); + cntkctl |= (divider << 4) | (1 << 2) | (1 << 1); asm volatile("msr cntkctl_el1, %0" : : "r" (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 c463ce9..24dc140 100644 --- a/include/clocksource/arm_arch_timer.h +++ b/include/clocksource/arm_arch_timer.h @@ -29,6 +29,8 @@ #define ARCH_TIMER_PHYS_ACCESS 0 #define ARCH_TIMER_VIRT_ACCESS 1 +#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/