From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8343FC64EB4 for ; Sat, 1 Dec 2018 01:01:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4EC7320673 for ; Sat, 1 Dec 2018 01:01:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4EC7320673 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=telegraphics.com.au Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727156AbeLAMMR (ORCPT ); Sat, 1 Dec 2018 07:12:17 -0500 Received: from kvm5.telegraphics.com.au ([98.124.60.144]:38158 "EHLO kvm5.telegraphics.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726895AbeLAMLb (ORCPT ); Sat, 1 Dec 2018 07:11:31 -0500 Received: by kvm5.telegraphics.com.au (Postfix, from userid 502) id 6DACE28201; Fri, 30 Nov 2018 20:00:15 -0500 (EST) To: Geert Uytterhoeven Cc: Andreas Schwab , Arnd Bergmann , Stephen N Chivers , Thomas Gleixner , Kars de Jong , Daniel Lezcano , Michael Schmitz , John Stultz , Linus Walleij , linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org Message-Id: In-Reply-To: References: From: Finn Thain Subject: [PATCH v4 12/14] m68k: mvme147: Handle timer counter overflow Date: Sat, 01 Dec 2018 11:53:10 +1100 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Reading the timer counter races with timer overflow (and the corresponding interrupt). This is resolved by reading the overflow register and taking this value into account. The interrupt handler must clear the overflow register when it eventually executes. Suggested-by: Thomas Gleixner Signed-off-by: Finn Thain --- TODO: find a spare counter for the clocksource, rather than hanging it off the HZ timer. --- arch/m68k/include/asm/mvme147hw.h | 1 + arch/m68k/mvme147/config.c | 21 +++++++++++---------- 2 files changed, 12 insertions(+), 10 deletions(-) diff --git a/arch/m68k/include/asm/mvme147hw.h b/arch/m68k/include/asm/mvme147hw.h index 7c3dd513128e..257b29184af9 100644 --- a/arch/m68k/include/asm/mvme147hw.h +++ b/arch/m68k/include/asm/mvme147hw.h @@ -66,6 +66,7 @@ struct pcc_regs { #define PCC_INT_ENAB 0x08 #define PCC_TIMER_INT_CLR 0x80 +#define PCC_TIMER_CLR_OVF 0x04 #define PCC_LEVEL_ABORT 0x07 #define PCC_LEVEL_SERIAL 0x04 diff --git a/arch/m68k/mvme147/config.c b/arch/m68k/mvme147/config.c index c44a254e8a8c..545a1fe0e119 100644 --- a/arch/m68k/mvme147/config.c +++ b/arch/m68k/mvme147/config.c @@ -118,7 +118,7 @@ static irqreturn_t mvme147_timer_int (int irq, void *dev_id) local_irq_save(flags); m147_pcc->t1_int_cntrl = PCC_TIMER_INT_CLR; - m147_pcc->t1_int_cntrl = PCC_INT_ENAB|PCC_LEVEL_TIMER1; + m147_pcc->t1_cntrl = PCC_TIMER_CLR_OVF; clk_total += PCC_TIMER_CYCLES; timer_routine(0, NULL); local_irq_restore(flags); @@ -144,21 +144,22 @@ void mvme147_sched_init (irq_handler_t timer_routine) clocksource_register_hz(&mvme147_clk, PCC_TIMER_CLOCK_FREQ); } -/* XXX There are race hazards in this code XXX */ static u64 mvme147_read_clk(struct clocksource *cs) { unsigned long flags; - volatile unsigned short *cp = (volatile unsigned short *)0xfffe1012; - unsigned short n; + u8 overflow, tmp; + u16 count; u32 ticks; local_irq_save(flags); - n = *cp; - while (n != *cp) - n = *cp; - - n -= PCC_TIMER_PRELOAD; - ticks = clk_total + n; + tmp = m147_pcc->t1_cntrl >> 4; + count = m147_pcc->t1_count; + overflow = m147_pcc->t1_cntrl >> 4; + if (overflow != tmp) + count = m147_pcc->t1_count; + count -= PCC_TIMER_PRELOAD; + ticks = count + overflow * PCC_TIMER_CYCLES; + ticks += clk_total; local_irq_restore(flags); return ticks; -- 2.18.1