Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933456Ab3FRRHG (ORCPT ); Tue, 18 Jun 2013 13:07:06 -0400 Received: from service87.mimecast.com ([91.220.42.44]:45957 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933107Ab3FRRHF (ORCPT ); Tue, 18 Jun 2013 13:07:05 -0400 From: Sudeep KarkadaNagesha To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Sudeep.KarkadaNagesha@arm.com, linux@arm.linux.org.uk, catalin.marinas@arm.com, will.deacon@arm.com, mark.rutland@arm.com, marc.zyngier@arm.com, tglx@linutronix.de, Mathieu Poirier Subject: [PATCH 1/4] drivers: clocksource: configure event stream for ARM arch timer Date: Tue, 18 Jun 2013 18:07:00 +0100 Message-Id: <1371575223-21702-2-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1371575223-21702-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> References: <1371575223-21702-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-OriginalArrivalTime: 18 Jun 2013 17:07:01.0185 (UTC) FILETIME=[3FA8A310:01CE6C46] X-MC-Unique: 113061818070206901 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 r5IH8sFH002387 Content-Length: 4052 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 Signed-off-by: Will Deacon Reviewed-by: Lorenzo Pieralisi --- 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 accefe0..75c8ec3 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 __cpuinit arch_counter_set_user_access(void) +static inline void __cpuinit 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 d56ed11..5fcaa6f 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 __cpuinit arch_counter_set_user_access(void) +static inline void __cpuinit 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 053d846..11aaf06 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 __cpuinit 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 __cpuinit 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/