| Message ID | 20190316222504.27170-2-tomli@tomli.me (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fbdev: sm712fb: fix a series of lockups, crashes and gliches. | expand |
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
diff --git a/drivers/video/fbdev/sm712fb.c b/drivers/video/fbdev/sm712fb.c index 502d0de2feec..d05379affa32 100644 --- a/drivers/video/fbdev/sm712fb.c +++ b/drivers/video/fbdev/sm712fb.c @@ -1171,8 +1171,12 @@ static void sm7xx_set_timing(struct smtcfb_info *sfb) 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++)
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+ --- drivers/video/fbdev/sm712fb.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)