Hi Jani, On Thu, Mar 7, 2019 at 10:00 AM Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote: > On Thu, 07 Mar 2019, Tom Li <tomli@xxxxxxxx> wrote: > > As you may have noticed, recently I've been working on a reworked version > > of sm712fb, and planned to convert it to a DRM/KMS driver. Besides using > > it on embedded/non-x86 systems, I thought it would be a good idea to support > > histrocial x86 laptops with this VGA chipset as well, so I've acquired a > > machine for testing. > > > > However, soon I found a nasty problem. The BIOS does not reset the chip > > on boot! Like most graphics controller of that era, sm712 chipset has a > > VGA compatible mode and a 2D framebuffer mode. The power-on default is > > VGA. The BIOS writer just assumed this, and does nothing to reinitialize > > it. If one uses the framebuffer driver under Linux, once the machine reboots, > > the entire LCD panel becomes a piece of garbage. > > > > AFAIK, the framebuffer driver would be running throughout the kernel's life- > > cycle, is it really possible to workaround this issue by restoring on VGA > > state upon reboot? > > It's possible to do this using a reboot notifier. I am not sure if there > are better ways to achieve the same, but there's at least one example of > using reboot notifiers to achieve the exact same goal. > > See drivers/video/fbdev/aty/atyfb_base.c, look for > register_reboot_notifier(). Or a shutdown handler, which is more device-centric? (cfr. "[3/4] fbdev: atafb: Fix broken frame buffer after kexec", https://patchwork.kernel.org/patch/10814381/). Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
