From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sudip Mukherjee Date: Sun, 31 Mar 2019 12:18:51 +0000 Subject: Re: [PATCH 1/8] fbdev: sm712fb: fix white screen of death on reboot, don't set CR3B-CR3F. Message-Id: <20190331121851.h3j2pud6yhelsknr@debian> List-Id: References: <20190316222504.27170-1-tomli@tomli.me> <20190316222504.27170-2-tomli@tomli.me> In-Reply-To: <20190316222504.27170-2-tomli@tomli.me> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Yifeng Li Cc: Teddy Wang , Bartlomiej Zolnierkiewicz , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org On Sun, Mar 17, 2019 at 06:24:57AM +0800, Yifeng Li wrote: > On a Thinkpad s30 (Pentium III / i440MX, Lynx3DM), rebooting with > sm712fb framebuffer driver would cause a white screen of death on > the next POST, presumably the proper timings for the LCD panel was > not reprogrammed properly by the BIOS. > > Experiments showed a few CRTC Scratch Registers, including CRT3D, > CRT3E and CRT3F may be used internally by BIOS as some flags. CRT3B is > a hardware testing register, we shouldn't mess with it. CRT3C has > blanking signal and line compare control, which is not needed for this > driver. > > Stop writing to CR3B-CR3F (a.k.a CRT3B-CRT3F) registers. Even if these > registers don't have side-effect on other systems, writing to them is > also highly questionable. > > Signed-off-by: Yifeng Li > Cc: stable@vger.kernel.org # v4.4+ Tested-by: Sudip Mukherjee -- Regards Sudip