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[209.132.180.67]) by mx.google.com with ESMTP id i69si6880201plb.17.2019.03.08.02.36.32; Fri, 08 Mar 2019 02:36:48 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@tomli.me header.s=1490979754 header.b=Kjx6zL4e; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=tomli.me Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726424AbfCHKfu (ORCPT + 99 others); Fri, 8 Mar 2019 05:35:50 -0500 Received: from tomli.me ([153.92.126.73]:49410 "EHLO tomli.me" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726261AbfCHKfu (ORCPT ); Fri, 8 Mar 2019 05:35:50 -0500 Received: from tomli.me (localhost [127.0.0.1]) by tomli.me (OpenSMTPD) with ESMTP id f1c332d7; Fri, 8 Mar 2019 10:35:47 +0000 (UTC) X-HELO: localhost.localdomain Authentication-Results: tomli.me; auth=pass (login) smtp.auth=tomli Received: from Unknown (HELO localhost.localdomain) (2402:f000:1:1501:200:5efe:72f4:b31) by tomli.me (qpsmtpd/0.95) with ESMTPSA (DHE-RSA-CHACHA20-POLY1305 encrypted); Fri, 08 Mar 2019 10:35:46 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=tomli.me; h=date:from:to:cc:subject:message-id:references:mime-version:content-type:in-reply-to; s=1490979754; bh=t9wemqcEPJHkmqGG1fVbiGvM/fm7piN+icR+Ynx6f/o=; b=Kjx6zL4e3/ejaNt60TP/meuBpEcb+zXdiZioZ3dX0Ec3yil9NKRu4CNxRQ9OAW0LNMyLFHJomHlCn+LgUvnN6YlTOSyVWJrXVItzoD+XN7LwVk6jTKIkqJ36vykdAt9NOVPHS5oh9i6C5oqLr8MbK3vwJZx6Nf7WtqKBz+5y8AuK+SENE/KDW8Ql76c2c9yloRVR5F6vcUdFqq1i9a1wqnfdbN6Phm1ftey2lKA2gNr31qbNVejZd9g+ZoG6Bk2lEk3FqeTZktMN70EaOjoKNXSnFn+ifc1RKX4t9q3j79VNIcmnv4hcAMC0j70Gg0Ku9Ee+0/w7i5XmCvruplGoRA== Date: Fri, 8 Mar 2019 18:35:36 +0800 From: Tom Li To: Geert Uytterhoeven Cc: Jani Nikula , Linux Fbdev development list , DRI Development , Linux Kernel Mailing List , Bartlomiej Zolnierkiewicz , Sudip Mukherjee , Teddy Wang Subject: Re: Is it possible to reset graphics controller on reboot in a framebuffer driver? Message-ID: <20190308103536.GA17258@localhost.localdomain> References: <20190307051641.GA7012@localhost.localdomain> <871s3jm532.fsf@intel.com> <20190307213759.GA14798@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 08, 2019 at 10:13:58AM +0100, Geert Uytterhoeven wrote: > Hi Tom, > > If the kernel just crashes, of course all of that doesn't happen. > Is your graphics card reset when the reset button is pressed, or only on > cold power on? It's a laptop, so it doesn't have a reset button. I've tried reboot=cold/warn but apparently it doesn't make any difference. So I think only a cold boot can reset the graphics card. > On Thu, Mar 7, 2019 at 10:38 PM Tom Li wrote: > > Nevertheless, does it mean there's no way to prevent it from happening if the > > user issues a emergency reboot? Like an automatic reboot after a kernel panic, > > or a SysRq-B reboot. > > If Linux performs a reboot, it calls the shutdown handlers. > I think that includes reboot on panic, or SysRq-B, but I'd have to check to > be 100% sure. Okay, glad to hear that. If it works for SysRq-B or panic reboot, I think it would be enough. After all, hard kernel crashes are rare nowadays, and most crashes are hard lockups. In case it happens, the user just presses the power button to halt. NMI watchdog reset is still an issue though, but I don't think people who are playing with those ~1999-2002 hardware (like this one) is actually using it. Anyway, In this case, I think putting a special note in the documentation, and raising a warning in dmesg (WARNING: LCD output may be corrupted on reset, read ./Documentation/fb/sm712fb.txt!) would be adequate. Thanks, Tom Li