| From 8069053880e0ee3a75fd6d7e0a30293265fe3de4 Mon Sep 17 00:00:00 2001 |
| From: Yifeng Li <tomli@tomli.me> |
| Date: Mon, 1 Apr 2019 17:46:58 +0200 |
| Subject: fbdev: sm712fb: fix white screen of death on reboot, don't set CR3B-CR3F |
| |
| From: Yifeng Li <tomli@tomli.me> |
| |
| commit 8069053880e0ee3a75fd6d7e0a30293265fe3de4 upstream. |
| |
| 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> |
| Tested-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com> |
| Cc: Teddy Wang <teddy.wang@siliconmotion.com> |
| Cc: <stable@vger.kernel.org> # v4.4+ |
| Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/video/fbdev/sm712fb.c | 6 +++++- |
| 1 file changed, 5 insertions(+), 1 deletion(-) |
| |
| --- a/drivers/video/fbdev/sm712fb.c |
| +++ b/drivers/video/fbdev/sm712fb.c |
| @@ -1172,8 +1172,12 @@ static void sm7xx_set_timing(struct smtc |
| smtc_crtcw(i, vgamode[j].init_cr00_cr18[i]); |
| |
| /* init CRTC register CR30 - CR4D */ |
| - for (i = 0; i < SIZE_CR30_CR4D; i++) |
| + for (i = 0; i < SIZE_CR30_CR4D; i++) { |
| + if ((i + 0x30) >= 0x3B && (i + 0x30) <= 0x3F) |
| + /* side-effect, don't write to CR3B-CR3F */ |
| + continue; |
| smtc_crtcw(i + 0x30, vgamode[j].init_cr30_cr4d[i]); |
| + } |
| |
| /* init CRTC register CR90 - CRA7 */ |
| for (i = 0; i < SIZE_CR90_CRA7; i++) |
