Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934861Ab3GRXZy (ORCPT ); Thu, 18 Jul 2013 19:25:54 -0400 Received: from smtp.codeaurora.org ([198.145.11.231]:58717 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934595Ab3GRXVg (ORCPT ); Thu, 18 Jul 2013 19:21:36 -0400 From: Stephen Boyd To: John Stultz Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Thomas Gleixner , Russell King , Catalin Marinas , Will Deacon , Christopher Covington Subject: [PATCH v4 04/17] sched_clock: Add support for >32 bit sched_clock Date: Thu, 18 Jul 2013 16:21:17 -0700 Message-Id: <1374189690-10810-5-git-send-email-sboyd@codeaurora.org> X-Mailer: git-send-email 1.8.3.3.754.g9c3c367 In-Reply-To: <1374189690-10810-1-git-send-email-sboyd@codeaurora.org> References: <1374189690-10810-1-git-send-email-sboyd@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5939 Lines: 174 The ARM architected system counter has at least 56 usable bits. Add support for counters with more than 32 bits to the generic sched_clock implementation so we can increase the time between wakeups due to dealing with wrap-around on these devices while benefiting from the irqtime accounting and suspend/resume handling that the generic sched_clock code already has. On my system using 56 bits over 32 bits changes the wraparound time from a few minutes to an hour. For faster running counters (GHz range) this is even more important because we may not be able to execute the timer in time to deal with the wraparound if only 32 bits are used. We choose a maxsec value of 3600 seconds because we assume no system will go idle for more than an hour. In the future we may need to increase this value. Note: All users should switch over to the 64-bit read function so we can remove setup_sched_clock() in favor of sched_clock_register(). Cc: Russell King Signed-off-by: Stephen Boyd --- include/linux/sched_clock.h | 2 ++ kernel/time/sched_clock.c | 46 +++++++++++++++++++++++++++++++-------------- 2 files changed, 34 insertions(+), 14 deletions(-) diff --git a/include/linux/sched_clock.h b/include/linux/sched_clock.h index fa7922c..eca7abe 100644 --- a/include/linux/sched_clock.h +++ b/include/linux/sched_clock.h @@ -15,6 +15,8 @@ static inline void sched_clock_postinit(void) { } #endif extern void setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate); +extern void sched_clock_register(u64 (*read)(void), int bits, + unsigned long rate); extern unsigned long long (*sched_clock_func)(void); diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c index a269890b..3aa83ba 100644 --- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -16,11 +16,12 @@ #include #include #include +#include struct clock_data { ktime_t wrap_kt; u64 epoch_ns; - u32 epoch_cyc; + u64 epoch_cyc; seqcount_t seq; unsigned long rate; u32 mult; @@ -37,14 +38,25 @@ static struct clock_data cd = { .mult = NSEC_PER_SEC / HZ, }; -static u32 __read_mostly sched_clock_mask = 0xffffffff; +static u64 __read_mostly sched_clock_mask; -static u32 notrace jiffy_sched_clock_read(void) +static u64 notrace jiffy_sched_clock_read(void) { - return (u32)(jiffies - INITIAL_JIFFIES); + /* + * We don't need to use get_jiffies_64 on 32-bit arches here + * because we register with BITS_PER_LONG + */ + return (u64)(jiffies - INITIAL_JIFFIES); +} + +static u32 __read_mostly (*read_sched_clock_32)(void); + +static u64 notrace read_sched_clock_32_wrapper(void) +{ + return read_sched_clock_32(); } -static u32 __read_mostly (*read_sched_clock)(void) = jiffy_sched_clock_read; +static u64 __read_mostly (*read_sched_clock)(void) = jiffy_sched_clock_read; static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift) { @@ -54,8 +66,8 @@ static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift) static unsigned long long notrace sched_clock_32(void) { u64 epoch_ns; - u32 epoch_cyc; - u32 cyc; + u64 epoch_cyc; + u64 cyc; unsigned long seq; if (cd.suspended) @@ -78,7 +90,7 @@ static unsigned long long notrace sched_clock_32(void) static void notrace update_sched_clock(void) { unsigned long flags; - u32 cyc; + u64 cyc; u64 ns; cyc = read_sched_clock(); @@ -101,7 +113,8 @@ static enum hrtimer_restart sched_clock_poll(struct hrtimer *hrt) return HRTIMER_RESTART; } -void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) +void __init sched_clock_register(u64 (*read)(void), int bits, + unsigned long rate) { unsigned long r; u64 res, wrap; @@ -110,14 +123,13 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) if (cd.rate > rate) return; - BUG_ON(bits > 32); WARN_ON(!irqs_disabled()); read_sched_clock = read; - sched_clock_mask = (1 << bits) - 1; + sched_clock_mask = CLOCKSOURCE_MASK(bits); cd.rate = rate; /* calculate the mult/shift to convert counter ticks to ns. */ - clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 0); + clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 3600); r = rate; if (r >= 4000000) { @@ -130,7 +142,7 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) r_unit = ' '; /* calculate how many ns until we wrap */ - wrap = cyc_to_ns((1ULL << bits) - 1, cd.mult, cd.shift); + wrap = clocks_calc_max_nsecs(cd.mult, cd.shift, 0, sched_clock_mask); cd.wrap_kt = ns_to_ktime(wrap - (wrap >> 3)); /* calculate the ns resolution of this counter */ @@ -158,6 +170,12 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) pr_debug("Registered %pF as sched_clock source\n", read); } +void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) +{ + read_sched_clock_32 = read; + sched_clock_register(read_sched_clock_32_wrapper, bits, rate); +} + unsigned long long __read_mostly (*sched_clock_func)(void) = sched_clock_32; unsigned long long notrace sched_clock(void) @@ -172,7 +190,7 @@ void __init sched_clock_postinit(void) * make it the final one one. */ if (read_sched_clock == jiffy_sched_clock_read) - setup_sched_clock(jiffy_sched_clock_read, 32, HZ); + sched_clock_register(jiffy_sched_clock_read, BITS_PER_LONG, HZ); update_sched_clock(); hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- 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/