Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751282Ab3HTN1s (ORCPT ); Tue, 20 Aug 2013 09:27:48 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:64040 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751049Ab3HTN1r (ORCPT ); Tue, 20 Aug 2013 09:27:47 -0400 Date: Tue, 20 Aug 2013 14:27:12 +0100 From: Will Deacon To: Sudeep KarkadaNagesha Cc: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Lorenzo Pieralisi , Catalin Marinas , Thomas Gleixner , Daniel Lezcano Subject: Re: [PATCH v3 4/6] ARM64: arch_timer: configure and enable event stream Message-ID: <20130820132712.GE26129@mudshark.cambridge.arm.com> References: <1374492082-13686-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> <1376414984-14182-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> <1376414984-14182-5-git-send-email-Sudeep.KarkadaNagesha@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1376414984-14182-5-git-send-email-Sudeep.KarkadaNagesha@arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3364 Lines: 87 Hi Sudeep, Couple of comments inline... On Tue, Aug 13, 2013 at 06:29:42PM +0100, Sudeep KarkadaNagesha wrote: > From: Sudeep KarkadaNagesha > > This patch configures the event stream frequency and enables it. > It also adds the hwcaps as well as compat-specific definitions to > the user to detect this event stream feature. > > Cc: Catalin Marinas > Reviewed-by: Lorenzo Pieralisi > Signed-off-by: Will Deacon > [sudeep: moving ARM/ARM64 changes into separate patches] > Signed-off-by: Sudeep KarkadaNagesha > --- > arch/arm64/include/asm/arch_timer.h | 12 ++++++++++-- > arch/arm64/include/asm/hwcap.h | 4 +++- > arch/arm64/include/uapi/asm/hwcap.h | 1 + > arch/arm64/kernel/setup.c | 1 + > 4 files changed, 15 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h > index 69f5c8e..43f322a 100644 > --- a/arch/arm64/include/asm/arch_timer.h > +++ b/arch/arm64/include/asm/arch_timer.h > @@ -106,14 +106,22 @@ static inline void arch_counter_set_user_access(int divider) > /* Disable user access to the timers and the physical counter. */ > cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN > | ARCH_TIMER_USR_VT_ACCESS_EN > + | ARCH_TIMER_EVT_TRIGGER_MASK > | ARCH_TIMER_USR_PCT_ACCESS_EN); > > - /* Enable user access to the virtual counter. */ > - cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN; > + /* Enable event stream and user access to the virtual counter */ > + cntkctl |= (divider << ARCH_TIMER_EVT_TRIGGER_SHIFT) > + | ARCH_TIMER_VIRT_EVT_EN > + | ARCH_TIMER_USR_VCT_ACCESS_EN; > > asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl)); > } > > +static inline void arch_timer_set_hwcap_evtstrm(void) > +{ > + elf_hwcap |= HWCAP_EVTSTRM; > +} > + > static inline u64 arch_counter_get_cntvct(void) > { > u64 cval; > diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h > index 6d4482f..effd8f9 100644 > --- a/arch/arm64/include/asm/hwcap.h > +++ b/arch/arm64/include/asm/hwcap.h > @@ -30,6 +30,7 @@ > #define COMPAT_HWCAP_IDIVA (1 << 17) > #define COMPAT_HWCAP_IDIVT (1 << 18) > #define COMPAT_HWCAP_IDIV (COMPAT_HWCAP_IDIVA|COMPAT_HWCAP_IDIVT) > +#define COMPAT_HWCAP_EVTSTRM (1 << 21) Looking at the context, we should also add COMPAT_HWCAP_LPAE as a separate patch (not part of this series). > #ifndef __ASSEMBLY__ > /* > @@ -41,7 +42,8 @@ > COMPAT_HWCAP_FAST_MULT|COMPAT_HWCAP_EDSP|\ > COMPAT_HWCAP_TLS|COMPAT_HWCAP_VFP|\ > COMPAT_HWCAP_VFPv3|COMPAT_HWCAP_VFPv4|\ > - COMPAT_HWCAP_NEON|COMPAT_HWCAP_IDIV) > + COMPAT_HWCAP_NEON|COMPAT_HWCAP_IDIV|\ > + COMPAT_HWCAP_EVTSTRM) So here you're hardcoding COMPAT_HWCAP_EVTSTRM in the COMPAT_ELF_HWCAP, yet we only enable the native one from the arch-timer driver. The question then is "Can we rely on the event-stream working for AArch64?". If so, we don't need the native hwcap at all. If not, then we need to make the compat hwcap dynamic. Will -- 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/