Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756403Ab3HLNcG (ORCPT ); Mon, 12 Aug 2013 09:32:06 -0400 Received: from service87.mimecast.com ([91.220.42.44]:45136 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756125Ab3HLNbq convert rfc822-to-8bit (ORCPT ); Mon, 12 Aug 2013 09:31:46 -0400 Message-ID: <5208E3E2.4010505@arm.com> Date: Mon, 12 Aug 2013 14:32:18 +0100 From: Sudeep KarkadaNagesha User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: Catalin Marinas CC: Sudeep KarkadaNagesha , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Mark Rutland , Lorenzo Pieralisi , Russell King , Will Deacon , Mathieu Poirier Subject: Re: [PATCH v3 1/3] drivers: clocksource: configure event stream for ARM arch timer References: <1374492082-13686-2-git-send-email-Sudeep.KarkadaNagesha@arm.com> <1374745537-30389-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> In-Reply-To: <1374745537-30389-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> X-OriginalArrivalTime: 12 Aug 2013 13:31:43.0919 (UTC) FILETIME=[491683F0:01CE9760] X-MC-Unique: 113081214314405901 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5627 Lines: 166 On 25/07/13 10:45, Sudeep KarkadaNagesha wrote: > 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. > > This patch also adds the hwcaps for the same, so that userspace can > detect this feature. > > Cc: Mathieu Poirier > Reviewed-by: Lorenzo Pieralisi > Signed-off-by: Will Deacon > --- > arch/arm/include/asm/arch_timer.h | 6 ++++-- > arch/arm/include/uapi/asm/hwcap.h | 1 + > arch/arm/kernel/setup.c | 1 + > arch/arm64/include/asm/arch_timer.h | 6 +++--- > drivers/clocksource/arm_arch_timer.c | 9 ++++++++- > include/clocksource/arm_arch_timer.h | 2 ++ > 6 files changed, 19 insertions(+), 6 deletions(-) > > ------------>8--------------------- > > Hi, > > This version adds the hwcaps for publishing the event stream feature to the > userspace. > Hi Catalin, If you are OK with this patch, can I have your ACK ? Regards, Sudeep > This patch is now rebased on rmk's fixes branch as it conflicts with ab8d46c0 > "ARM: 7788/1: elf: fix lpae hwcap feature reporting in proc/cpuinfo" > > Regards, > Sudeep > > diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h > index e406d57..8963877 100644 > --- a/arch/arm/include/asm/arch_timer.h > +++ b/arch/arm/include/asm/arch_timer.h > @@ -89,16 +89,18 @@ 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)); > + elf_hwcap |= HWCAP_EVTSTRM; > } > #endif > > diff --git a/arch/arm/include/uapi/asm/hwcap.h b/arch/arm/include/uapi/asm/hwcap.h > index 6d34d08..7dcc10d 100644 > --- a/arch/arm/include/uapi/asm/hwcap.h > +++ b/arch/arm/include/uapi/asm/hwcap.h > @@ -26,5 +26,6 @@ > #define HWCAP_VFPD32 (1 << 19) /* set if VFP has 32 regs (not 16) */ > #define HWCAP_IDIV (HWCAP_IDIVA | HWCAP_IDIVT) > #define HWCAP_LPAE (1 << 20) > +#define HWCAP_EVTSTRM (1 << 21) > > #endif /* _UAPI__ASMARM_HWCAP_H */ > diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c > index 96286cb..5191956 100644 > --- a/arch/arm/kernel/setup.c > +++ b/arch/arm/kernel/setup.c > @@ -973,6 +973,7 @@ static const char *hwcap_str[] = { > "idivt", > "vfpd32", > "lpae", > + "evtstrm", > NULL > }; > > 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); > -- 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/