Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752123AbaKZMsC (ORCPT ); Wed, 26 Nov 2014 07:48:02 -0500 Received: from mail-wg0-f52.google.com ([74.125.82.52]:54759 "EHLO mail-wg0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750963AbaKZMr7 (ORCPT ); Wed, 26 Nov 2014 07:47:59 -0500 Message-ID: <5475CBF9.8050706@linaro.org> Date: Wed, 26 Nov 2014 13:47:53 +0100 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Sonny Rao , linux-arm-kernel@lists.infradead.org CC: linux-kernel@vger.kernel.org, dianders@chromium.org, Lorenzo Pieralisi , Sudeep KarkadaNagesha , Olof Johansson , Thomas Gleixner , Will Deacon , Catalin Marinas , Russell King , Sudeep Holla , Mark Rutland , Stephen Boyd , Marc Zyngier , stable@vger.kernel.org Subject: Re: [PATCH v5] clocksource: arch_timer: Fix code to use physical timers when requested References: <1416812564-26465-1-git-send-email-sonnyrao@chromium.org> In-Reply-To: <1416812564-26465-1-git-send-email-sonnyrao@chromium.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/24/2014 08:02 AM, Sonny Rao wrote: > This is a bug fix for using physical arch timers when > the arch_timer_use_virtual boolean is false. It restores the > arch_counter_get_cntpct() function after removal in > > 0d651e4e "clocksource: arch_timer: use virtual counters" > > We need this on certain ARMv7 systems which are architected like this: > > * The firmware doesn't know and doesn't care about hypervisor mode and > we don't want to add the complexity of hypervisor there. > > * The firmware isn't involved in SMP bringup or resume. > > * The ARCH timer come up with an uninitialized offset between the > virtual and physical counters. Each core gets a different random > offset. > > * The device boots in "Secure SVC" mode. > > * Nothing has touched the reset value of CNTHCTL.PL1PCEN or > CNTHCTL.PL1PCTEN (both default to 1 at reset) > > One example of such as system is RK3288 where it is much simpler to > use the physical counter since there's nobody managing the offset and > each time a core goes down and comes back up it will get reinitialized > to some other random value. > > Fixes: 0d651e4e65e9 ("clocksource: arch_timer: use virtual counters") > Cc: stable@vger.kernel.org > Signed-off-by: Sonny Rao > Acked-by: Olof Johansson Acked-by: Daniel Lezcano > --- > v2: Add fixes tag to commit message, cc stable, copy Doug's > description of the systems which need this in commit message. > v3: Don't change the memory-mapped physical timer/counter code > v4: remove the memory-mapped physical counter code since it's not used > v5: rebase and make AArch64 version of arch_counter_get_cntpct call BUG() > --- > arch/arm/include/asm/arch_timer.h | 9 +++++++++ > arch/arm64/include/asm/arch_timer.h | 9 +++++++++ > drivers/clocksource/arm_arch_timer.c | 5 ++++- > 3 files changed, 22 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h > index 92793ba..d4ebf56 100644 > --- a/arch/arm/include/asm/arch_timer.h > +++ b/arch/arm/include/asm/arch_timer.h > @@ -78,6 +78,15 @@ static inline u32 arch_timer_get_cntfrq(void) > return val; > } > > +static inline u64 arch_counter_get_cntpct(void) > +{ > + u64 cval; > + > + isb(); > + asm volatile("mrrc p15, 0, %Q0, %R0, c14" : "=r" (cval)); > + return cval; > +} > + > static inline u64 arch_counter_get_cntvct(void) > { > u64 cval; > diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h > index f190971..b1fa4e6 100644 > --- a/arch/arm64/include/asm/arch_timer.h > +++ b/arch/arm64/include/asm/arch_timer.h > @@ -104,6 +104,15 @@ static inline void arch_timer_set_cntkctl(u32 cntkctl) > asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl)); > } > > +static inline u64 arch_counter_get_cntpct(void) > +{ > + /* > + * AArch64 kernel and user space mandate the use of CNTVCT. > + */ > + BUG(); > + return 0; > +} > + > static inline u64 arch_counter_get_cntvct(void) > { > u64 cval; > diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c > index 43005d4..1fa2af9 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -462,7 +462,10 @@ static void __init arch_counter_register(unsigned type) > > /* Register the CP15 based counter if we have one */ > if (type & ARCH_CP15_TIMER) { > - arch_timer_read_counter = arch_counter_get_cntvct; > + if (arch_timer_use_virtual) > + arch_timer_read_counter = arch_counter_get_cntvct; > + else > + arch_timer_read_counter = arch_counter_get_cntpct; > } else { > arch_timer_read_counter = arch_counter_get_cntvct_mem; > > -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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/