From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4157kD2vNszDr1b for ; Wed, 13 Jun 2018 11:01:40 +1000 (AEST) From: Ricardo Neri To: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Cc: Andi Kleen , Ashok Raj , Borislav Petkov , Tony Luck , "Ravi V. Shankar" , x86@kernel.org, sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Ricardo Neri , Jacob Pan , Clemens Ladisch , Arnd Bergmann , Philippe Ombredanne , Kate Stewart , "Rafael J. Wysocki" , iommu@lists.linux-foundation.org Subject: [RFC PATCH 08/23] x86/hpet: Calculate ticks-per-second in a separate function Date: Tue, 12 Jun 2018 17:57:28 -0700 Message-Id: <1528851463-21140-9-git-send-email-ricardo.neri-calderon@linux.intel.com> In-Reply-To: <1528851463-21140-1-git-send-email-ricardo.neri-calderon@linux.intel.com> References: <1528851463-21140-1-git-send-email-ricardo.neri-calderon@linux.intel.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , It is easier to compute the expiration times of an HPET timer by using its frequency (i.e., the number of times it ticks in a second) than its period, as given in the capabilities register. In addition to the HPET char driver, the HPET-based hardlockup detector will also need to know the timer's frequency. Thus, create a common function that both can use. Cc: Ashok Raj Cc: Andi Kleen Cc: Tony Luck Cc: Borislav Petkov Cc: Jacob Pan Cc: Clemens Ladisch Cc: Arnd Bergmann Cc: Philippe Ombredanne Cc: Kate Stewart Cc: "Rafael J. Wysocki" Cc: "Ravi V. Shankar" Cc: x86@kernel.org Cc: iommu@lists.linux-foundation.org Signed-off-by: Ricardo Neri --- drivers/char/hpet.c | 31 +++++++++++++++++++++++++------ include/linux/hpet.h | 1 + 2 files changed, 26 insertions(+), 6 deletions(-) diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c index be426eb..1c9584a 100644 --- a/drivers/char/hpet.c +++ b/drivers/char/hpet.c @@ -838,6 +838,29 @@ static unsigned long hpet_calibrate(struct hpets *hpetp) return ret; } +u64 hpet_get_ticks_per_sec(u64 hpet_caps) +{ + u64 ticks_per_sec, period; + + period = (hpet_caps & HPET_COUNTER_CLK_PERIOD_MASK) >> + HPET_COUNTER_CLK_PERIOD_SHIFT; /* fs, 10^-15 */ + + /* + * The frequency is the reciprocal of the period. The period is given + * femtoseconds per second. Thus, prepare a dividend to obtain the + * frequency in ticks per second. + */ + + /* 10^15 femtoseconds per second */ + ticks_per_sec = 1000000000000000uLL; + ticks_per_sec += period >> 1; /* round */ + + /* The quotient is put in the dividend. We drop the remainder. */ + do_div(ticks_per_sec, period); + + return ticks_per_sec; +} + int hpet_alloc(struct hpet_data *hdp) { u64 cap, mcfg; @@ -847,7 +870,6 @@ int hpet_alloc(struct hpet_data *hdp) size_t siz; struct hpet __iomem *hpet; static struct hpets *last; - unsigned long period; unsigned long long temp; u32 remainder; @@ -883,6 +905,8 @@ int hpet_alloc(struct hpet_data *hdp) cap = readq(&hpet->hpet_cap); + temp = hpet_get_ticks_per_sec(cap); + ntimer = ((cap & HPET_NUM_TIM_CAP_MASK) >> HPET_NUM_TIM_CAP_SHIFT) + 1; if (hpetp->hp_ntimer != ntimer) { @@ -899,11 +923,6 @@ int hpet_alloc(struct hpet_data *hdp) last = hpetp; - period = (cap & HPET_COUNTER_CLK_PERIOD_MASK) >> - HPET_COUNTER_CLK_PERIOD_SHIFT; /* fs, 10^-15 */ - temp = 1000000000000000uLL; /* 10^15 femtoseconds per second */ - temp += period >> 1; /* round */ - do_div(temp, period); hpetp->hp_tick_freq = temp; /* ticks per second */ printk(KERN_INFO "hpet%d: at MMIO 0x%lx, IRQ%s", diff --git a/include/linux/hpet.h b/include/linux/hpet.h index 8604564..e7b36bcf4 100644 --- a/include/linux/hpet.h +++ b/include/linux/hpet.h @@ -107,5 +107,6 @@ static inline void hpet_reserve_timer(struct hpet_data *hd, int timer) } int hpet_alloc(struct hpet_data *); +u64 hpet_get_ticks_per_sec(u64 hpet_caps); #endif /* !__HPET__ */ -- 2.7.4