Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261454AbVDWCtA (ORCPT ); Fri, 22 Apr 2005 22:49:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261464AbVDWCtA (ORCPT ); Fri, 22 Apr 2005 22:49:00 -0400 Received: from e33.co.us.ibm.com ([32.97.110.131]:26786 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S261454AbVDWCsw (ORCPT ); Fri, 22 Apr 2005 22:48:52 -0400 Subject: [PATCH] X86_64: fix hpet for systems that don't support legacy replacement (v. A3) From: john stultz To: Andrew Morton , vojtech@suse.cz Cc: lkml , Andi Kleen , Venkatesh Pallipadi In-Reply-To: <1113961261.19541.167.camel@cog.beaverton.ibm.com> References: <1113961261.19541.167.camel@cog.beaverton.ibm.com> Content-Type: text/plain Date: Fri, 22 Apr 2005 19:48:47 -0700 Message-Id: <1114224527.19541.278.camel@cog.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-2) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4882 Lines: 154 Andrew, All, Currently the x86-64 HPET code assumes the entire HPET implementation from the spec is present. This breaks on boxes that do not implement the optional legacy timer replacement functionality portion of the spec. This patch fixes this issue, allowing x86-64 systems that cannot use the HPET for the timer interrupt and RTC to still use the HPET as a time source. I've tested this patch on a system systems without HPET, with HPET but without legacy timer replacement, as well as HPET with legacy timer replacement. This version adds a minor check to cap the HPET counter value in gettimeoffset_hpet to avoid possible time inconsistencies. Please ignore the A2 version I sent to you earlier. Please consider for your tree. thanks -john Changelog: A0: First sent to lkml A1: Implemented suggestions from Venkatesh A2: Whitespace cleanup. A3: Cap gettimeoffset_hpet to avoid time inconsistencies linux-2.6.12-rc2_x86-64_hpet_nolegacy-fix_A3.patch ================================================== diff -Nru a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c --- a/arch/x86_64/kernel/time.c 2005-04-22 19:41:09 -07:00 +++ b/arch/x86_64/kernel/time.c 2005-04-22 19:41:09 -07:00 @@ -60,6 +60,7 @@ unsigned int cpu_khz; /* TSC clocks / usec, not used here */ static unsigned long hpet_period; /* fsecs / HPET clock */ unsigned long hpet_tick; /* HPET clocks / interrupt */ +static int hpet_use_timer; unsigned long vxtime_hz = PIT_TICK_RATE; int report_lost_ticks; /* command line option */ unsigned long long monotonic_base; @@ -101,7 +102,9 @@ static inline unsigned int do_gettimeoffset_hpet(void) { - return ((hpet_readl(HPET_COUNTER) - vxtime.last) * vxtime.quot) >> 32; + /* cap counter read to one tick to avoid inconsistencies */ + unsigned long counter = hpet_readl(HPET_COUNTER) - vxtime.last; + return (min(counter,hpet_tick) * vxtime.quot) >> 32; } unsigned int (*do_gettimeoffset)(void) = do_gettimeoffset_tsc; @@ -297,7 +300,7 @@ last_offset = vxtime.last; base = monotonic_base; - this_offset = hpet_readl(HPET_T0_CMP) - hpet_tick; + this_offset = hpet_readl(HPET_COUNTER); } while (read_seqretry(&xtime_lock, seq)); offset = (this_offset - last_offset); @@ -373,7 +376,14 @@ write_seqlock(&xtime_lock); - if (vxtime.hpet_address) { + if (vxtime.hpet_address) + offset = hpet_readl(HPET_COUNTER); + + if (hpet_use_timer) { + /* if we're using the hpet timer functionality, + * we can more accurately know the counter value + * when the timer interrupt occured. + */ offset = hpet_readl(HPET_T0_CMP) - hpet_tick; delay = hpet_readl(HPET_COUNTER) - offset; } else { @@ -794,17 +804,18 @@ * Set up timer 0, as periodic with first interrupt to happen at hpet_tick, * and period also hpet_tick. */ - - hpet_writel(HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL | + if (hpet_use_timer) { + hpet_writel(HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL | HPET_TN_32BIT, HPET_T0_CFG); - hpet_writel(hpet_tick, HPET_T0_CMP); - hpet_writel(hpet_tick, HPET_T0_CMP); /* AK: why twice? */ - + hpet_writel(hpet_tick, HPET_T0_CMP); + hpet_writel(hpet_tick, HPET_T0_CMP); /* AK: why twice? */ + cfg |= HPET_CFG_LEGACY; + } /* * Go! */ - cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY; + cfg |= HPET_CFG_ENABLE; hpet_writel(cfg, HPET_CFG); return 0; @@ -825,8 +836,7 @@ id = hpet_readl(HPET_ID); - if (!(id & HPET_ID_VENDOR) || !(id & HPET_ID_NUMBER) || - !(id & HPET_ID_LEGSUP)) + if (!(id & HPET_ID_VENDOR) || !(id & HPET_ID_NUMBER)) return -1; hpet_period = hpet_readl(HPET_PERIOD); @@ -836,6 +846,8 @@ hpet_tick = (1000000000L * (USEC_PER_SEC / HZ) + hpet_period / 2) / hpet_period; + hpet_use_timer = (id & HPET_ID_LEGSUP); + return hpet_timer_stop_set_go(hpet_tick); } @@ -892,9 +904,11 @@ set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec); - if (!hpet_init()) { + if (!hpet_init()) vxtime_hz = (1000000000000000L + hpet_period / 2) / hpet_period; + + if (hpet_use_timer) { cpu_khz = hpet_calibrate_tsc(); timename = "HPET"; } else { @@ -940,12 +954,12 @@ if (oem_force_hpet_timer()) notsc = 1; if (vxtime.hpet_address && notsc) { - timetype = "HPET"; + timetype = hpet_use_timer ? "HPET" : "PIT/HPET"; vxtime.last = hpet_readl(HPET_T0_CMP) - hpet_tick; vxtime.mode = VXTIME_HPET; do_gettimeoffset = do_gettimeoffset_hpet; } else { - timetype = vxtime.hpet_address ? "HPET/TSC" : "PIT/TSC"; + timetype = hpet_use_timer ? "HPET/TSC" : "PIT/TSC"; vxtime.mode = VXTIME_TSC; } - 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/