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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 08C0FC636C9 for ; Thu, 15 Jul 2021 18:45:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EAAE7613CF for ; Thu, 15 Jul 2021 18:45:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239865AbhGOSss (ORCPT ); Thu, 15 Jul 2021 14:48:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:48812 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236532AbhGOSrI (ORCPT ); Thu, 15 Jul 2021 14:47:08 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id F075761396; Thu, 15 Jul 2021 18:44:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626374654; bh=5TlJLhKCdmnQ2KEj8PczzkA6k7Gtm1NuaR798d7HNhI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vFvstwexy43pLmZBAdNr4kbJGeCfXb3b/fmDH4jXI4wLaxkH5m0T5ekUpXBEdPEoR R370xw5G4zHFr9NXpNao5+bOvgFQ+1K+tyJVIix990mflcVNsFNwuE3l56A9tjcDc0 g1jnUd3d3xkSrIW0DK03boBJHjIEVAGAXQscrWfg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Roman Stratiienko , Samuel Holland , Daniel Lezcano Subject: [PATCH 5.4 091/122] clocksource/arm_arch_timer: Improve Allwinner A64 timer workaround Date: Thu, 15 Jul 2021 20:38:58 +0200 Message-Id: <20210715182515.473663789@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210715182448.393443551@linuxfoundation.org> References: <20210715182448.393443551@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Samuel Holland commit 8b33dfe0ba1c84c1aab2456590b38195837f1e6e upstream. Bad counter reads are experienced sometimes when bit 10 or greater rolls over. Originally, testing showed that at least 10 lower bits would be set to the same value during these bad reads. However, some users still reported time skips. Wider testing revealed that on some chips, occasionally only the lowest 9 bits would read as the anomalous value. During these reads (which still happen only when bit 10), bit 9 would read as the correct value. Reduce the mask by one bit to cover these cases as well. Cc: stable@vger.kernel.org Fixes: c950ca8c35ee ("clocksource/drivers/arch_timer: Workaround for Allwinner A64 timer instability") Reported-by: Roman Stratiienko Signed-off-by: Samuel Holland Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20210515021439.55316-1-samuel@sholland.org Signed-off-by: Greg Kroah-Hartman --- drivers/clocksource/arm_arch_timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -348,7 +348,7 @@ static u64 notrace arm64_858921_read_cnt do { \ _val = read_sysreg(reg); \ _retries--; \ - } while (((_val + 1) & GENMASK(9, 0)) <= 1 && _retries); \ + } while (((_val + 1) & GENMASK(8, 0)) <= 1 && _retries); \ \ WARN_ON_ONCE(!_retries); \ _val; \