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authorYifeng Li <tomli@tomli.me>2019-04-01 17:46:58 +0200
committerBartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>2019-04-01 17:46:58 +0200
commit8069053880e0ee3a75fd6d7e0a30293265fe3de4 (patch)
tree230e8095fa1d546bbb0ca28dcce595c3f06a4ef4 /drivers/video
parent1d84353d205a953e2381044953b7fa31c8c9702d (diff)
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')
-rw-r--r--drivers/video/fbdev/sm712fb.c6
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++)