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| author | Yifeng Li <tomli@tomli.me> | 2019-04-01 17:46:58 +0200 |
|---|---|---|
| committer | Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> | 2019-04-01 17:46:58 +0200 |
| commit | 8069053880e0ee3a75fd6d7e0a30293265fe3de4 (patch) | |
| tree | 230e8095fa1d546bbb0ca28dcce595c3f06a4ef4 /drivers/video/fbdev | |
| parent | video: imsttfb: fix potential NULL pointer dereferences (diff) | |
| download | linux-8069053880e0ee3a75fd6d7e0a30293265fe3de4.tar.xz linux-8069053880e0ee3a75fd6d7e0a30293265fe3de4.zip | |
fbdev: sm712fb: fix white screen of death on reboot, don't set CR3B-CR3F
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>
Diffstat (limited to 'drivers/video/fbdev')
| -rw-r--r-- | drivers/video/fbdev/sm712fb.c | 6 |
1 files changed, 5 insertions, 1 deletions
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++) |