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 tomli@tomli.me Cc: stable@vger.kernel.org # v4.4+
Tested-by: Sudip Mukherjee sudipm.mukherjee@gmail.com
-- Regards Sudip