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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,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 D3C24C433DF for ; Mon, 12 Oct 2020 10:43:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8280520E65 for ; Mon, 12 Oct 2020 10:43:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602499388; bh=kkVGzqO7Lb+9K3Dk6vciWgEoxx1jza/xqmllWjBzjpk=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=QiOgaDazVmeshukhknGNEwc8FYs0W0Pe00G/7WQUqSsbLgORIiBmcz7aAJYDwF2nC qHEUsNUJQ8nxrN8wGVxVuHZ4/AP99cNEvJdyx+DTuFqoJ/0yB/hfZ+zxMKJfus4DOa 7ygTi+qhJQ75hdNR8Ri1lTX4V/eF8rZfSvTB5xis= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387669AbgJLKnH (ORCPT ); Mon, 12 Oct 2020 06:43:07 -0400 Received: from mail-ot1-f67.google.com ([209.85.210.67]:33232 "EHLO mail-ot1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387596AbgJLKnH (ORCPT ); Mon, 12 Oct 2020 06:43:07 -0400 Received: by mail-ot1-f67.google.com with SMTP id t15so15485051otk.0 for ; Mon, 12 Oct 2020 03:43:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=FNdG1MGcFaUsr7wF+6WWLM/nbNEIpoqNIuMa9ABnFws=; b=kDWR8jDF3ntP9ZKSnmE1YGWBEFyERtLn5uESub6Ycg5vENjrDQvGki5SdevPfTbuhq RugWAmHdJgugO8k7jg7hNX44rw7lZAohqfPa9H00jniUyBzpBdk9/9KI9wVZr44IxNBH qTjHoFS1+69myw6QRpVnAhcCCe2jOKbLqOLQJUpE2FPb/wPAyJCIIE3Q+eiT7oPMx9u+ sIDeVsDm+aU7bugFVvK9xvrBq1md9hNX4oLAVPY5P26ddHnPHvBrph7qW69RmeSO2y5Z c+2Z/9CLBcJS2fZ+bMrvTJomVZ0jrxh3x3ttJ0wVeUrfsJfvgMN1+x29RrmyNlSHGei4 ODoQ== X-Gm-Message-State: AOAM5316E26jGaoY4ZP4dt3aN1ddWpHwL/egRcqWdDC5TXm+Q+SOz3dO fax/jOLYnyjCYeBmRCjtqUz3HmLZjOEkkyM7W4YUnGdtG/s= X-Google-Smtp-Source: ABdhPJycKUQq7SanniBDFnT1Ib0LfuXgjk2ytgqWuAnKK/eBt0KfRNCgryGGEa5cyP4khbd0k+kN3skIXQ0+QNvsN30= X-Received: by 2002:a9d:734f:: with SMTP id l15mr19095652otk.260.1602499385988; Mon, 12 Oct 2020 03:43:05 -0700 (PDT) MIME-Version: 1.0 References: <20201010022606.27669-1-rui.zhang@intel.com> In-Reply-To: <20201010022606.27669-1-rui.zhang@intel.com> From: "Rafael J. Wysocki" Date: Mon, 12 Oct 2020 12:42:51 +0200 Message-ID: Subject: Re: [PATCH] acpi: reboot: fix racing after writing to ACPI RESET_REG To: Zhang Rui Cc: ACPI Devel Maling List , "Rafael J. Wysocki" , sukumar.ghorai@intel.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Sat, Oct 10, 2020 at 4:36 AM Zhang Rui wrote: > > According to the ACPI spec, "The system must reset immediately following > the write to the ACPI RESET_REG register.", but there are cases that the > system does not follow this and results in racing with the subsequetial > reboot mechanism, which brings unexpected behavior. > > Fix this by adding a 15ms delay after writing to the ACPI RESET_REG. > > Reported-by: Ghorai, Sukumar > Signed-off-by: Zhang Rui > --- > drivers/acpi/reboot.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c > index ca707f5b521d..88e6b083d702 100644 > --- a/drivers/acpi/reboot.c > +++ b/drivers/acpi/reboot.c > @@ -3,6 +3,7 @@ > #include > #include > #include > +#include > > #ifdef CONFIG_PCI > static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value) > @@ -66,4 +67,10 @@ void acpi_reboot(void) > acpi_reset(); > break; > } > + > + /* > + * delay for 15ms in case the system does not shutdown immediately after > + * writing to the ACPI reset register It would also be good to make a note of where the 15ms value comes from. Even if it has been guessed, it will still be good to know that, say, 5 years from now. > + */ > + mdelay(15); > } > -- > 2.17.1 >