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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 20FC3C2D0DB for ; Fri, 24 Jan 2020 09:53:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E861120718 for ; Fri, 24 Jan 2020 09:53:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579859599; bh=ogdsnwmeqaKBTAR36iRDzbokIcv1R80wiadMcy6VvZo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=z66OZTpW7ao6mg0e8bipsaWChiZhROg9GNRxFVJUs5WOF8AO63Pv6zKpFbrk7x2dN twtbPgJ9oB6J76g692A3gIB94HC9pPWuGfWfO712JQHrNK9eQZogm6DW9UUVnzNI7z Xm0DWv7EwnHSJ66OWMwEMDhUN9awbuVSsdUmV11g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388249AbgAXJxR (ORCPT ); Fri, 24 Jan 2020 04:53:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:55666 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387835AbgAXJxP (ORCPT ); Fri, 24 Jan 2020 04:53:15 -0500 Received: from localhost (unknown [145.15.244.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 873D0206D5; Fri, 24 Jan 2020 09:53:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579859594; bh=ogdsnwmeqaKBTAR36iRDzbokIcv1R80wiadMcy6VvZo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QSeB23kbBAXN3D09pn/bDrDEIr2WtUxOzs4inAf5ZZv3TccE+PIYq3g1QdHYCAaep gnEIGiVk260v6fEIdeyqlimQY2p+pk59GAecQ9RXLMbB6Dac8h1N6WC6dVQtXzox3V oDuKUcpFEK/PJUonDPNC1jA55zA73OvGM+q+a7rU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Finn Thain , Geert Uytterhoeven , Sasha Levin Subject: [PATCH 4.14 151/343] m68k: mac: Fix VIA timer counter accesses Date: Fri, 24 Jan 2020 10:29:29 +0100 Message-Id: <20200124092939.867579106@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200124092919.490687572@linuxfoundation.org> References: <20200124092919.490687572@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Finn Thain [ Upstream commit 0ca7ce7db771580433bf24454f7a1542bd326078 ] This resolves some bugs that affect VIA timer counter accesses. Avoid lost interrupts caused by reading the counter low byte register. Make allowance for the fact that the counter will be decremented to 0xFFFF before being reloaded. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Finn Thain Signed-off-by: Geert Uytterhoeven Signed-off-by: Sasha Levin --- arch/m68k/mac/via.c | 102 +++++++++++++++++++++++--------------------- 1 file changed, 53 insertions(+), 49 deletions(-) diff --git a/arch/m68k/mac/via.c b/arch/m68k/mac/via.c index 9f59a662ace57..7334245abf26f 100644 --- a/arch/m68k/mac/via.c +++ b/arch/m68k/mac/via.c @@ -54,16 +54,6 @@ static __u8 rbv_clear; static int gIER,gIFR,gBufA,gBufB; -/* - * Timer defs. - */ - -#define TICK_SIZE 10000 -#define MAC_CLOCK_TICK (783300/HZ) /* ticks per HZ */ -#define MAC_CLOCK_LOW (MAC_CLOCK_TICK&0xFF) -#define MAC_CLOCK_HIGH (MAC_CLOCK_TICK>>8) - - /* * On Macs with a genuine VIA chip there is no way to mask an individual slot * interrupt. This limitation also seems to apply to VIA clone logic cores in @@ -278,22 +268,6 @@ void __init via_init(void) } } -/* - * Start the 100 Hz clock - */ - -void __init via_init_clock(irq_handler_t func) -{ - via1[vACR] |= 0x40; - via1[vT1LL] = MAC_CLOCK_LOW; - via1[vT1LH] = MAC_CLOCK_HIGH; - via1[vT1CL] = MAC_CLOCK_LOW; - via1[vT1CH] = MAC_CLOCK_HIGH; - - if (request_irq(IRQ_MAC_TIMER_1, func, 0, "timer", func)) - pr_err("Couldn't register %s interrupt\n", "timer"); -} - /* * Debugging dump, used in various places to see what's going on. */ @@ -321,29 +295,6 @@ void via_debug_dump(void) } } -/* - * This is always executed with interrupts disabled. - * - * TBI: get time offset between scheduling timer ticks - */ - -u32 mac_gettimeoffset(void) -{ - unsigned long ticks, offset = 0; - - /* read VIA1 timer 2 current value */ - ticks = via1[vT1CL] | (via1[vT1CH] << 8); - /* The probability of underflow is less than 2% */ - if (ticks > MAC_CLOCK_TICK - MAC_CLOCK_TICK / 50) - /* Check for pending timer interrupt in VIA1 IFR */ - if (via1[vIFR] & 0x40) offset = TICK_SIZE; - - ticks = MAC_CLOCK_TICK - ticks; - ticks = ticks * 10000L / MAC_CLOCK_TICK; - - return (ticks + offset) * 1000; -} - /* * Flush the L2 cache on Macs that have it by flipping * the system into 24-bit mode for an instant. @@ -612,3 +563,56 @@ int via2_scsi_drq_pending(void) return via2[gIFR] & (1 << IRQ_IDX(IRQ_MAC_SCSIDRQ)); } EXPORT_SYMBOL(via2_scsi_drq_pending); + +/* timer and clock source */ + +#define VIA_CLOCK_FREQ 783360 /* VIA "phase 2" clock in Hz */ +#define VIA_TIMER_INTERVAL (1000000 / HZ) /* microseconds per jiffy */ +#define VIA_TIMER_CYCLES (VIA_CLOCK_FREQ / HZ) /* clock cycles per jiffy */ + +#define VIA_TC (VIA_TIMER_CYCLES - 2) /* including 0 and -1 */ +#define VIA_TC_LOW (VIA_TC & 0xFF) +#define VIA_TC_HIGH (VIA_TC >> 8) + +void __init via_init_clock(irq_handler_t timer_routine) +{ + if (request_irq(IRQ_MAC_TIMER_1, timer_routine, 0, "timer", NULL)) { + pr_err("Couldn't register %s interrupt\n", "timer"); + return; + } + + via1[vT1LL] = VIA_TC_LOW; + via1[vT1LH] = VIA_TC_HIGH; + via1[vT1CL] = VIA_TC_LOW; + via1[vT1CH] = VIA_TC_HIGH; + via1[vACR] |= 0x40; +} + +u32 mac_gettimeoffset(void) +{ + unsigned long flags; + u8 count_high; + u16 count, offset = 0; + + /* + * Timer counter wrap-around is detected with the timer interrupt flag + * but reading the counter low byte (vT1CL) would reset the flag. + * Also, accessing both counter registers is essentially a data race. + * These problems are avoided by ignoring the low byte. Clock accuracy + * is 256 times worse (error can reach 0.327 ms) but CPU overhead is + * reduced by avoiding slow VIA register accesses. + */ + + local_irq_save(flags); + count_high = via1[vT1CH]; + if (count_high == 0xFF) + count_high = 0; + if (count_high > 0 && (via1[vIFR] & VIA_TIMER_1_INT)) + offset = VIA_TIMER_CYCLES; + local_irq_restore(flags); + + count = count_high << 8; + count = VIA_TIMER_CYCLES - count + offset; + + return ((count * VIA_TIMER_INTERVAL) / VIA_TIMER_CYCLES) * 1000; +} -- 2.20.1