[PATCH 5.1 086/122] fbdev: sm712fb: fix brightness control on reboot, dont set SR30

Greg Kroah-Hartman
2019-05-23T19:30:20Z

From: Yifeng Li <tomli@tomli.me>

commit 5481115e25e42b9215f2619452aa99c95f08492f upstream.

On a Thinkpad s30 (Pentium III / i440MX, Lynx3DM), rebooting with
sm712fb framebuffer driver would cause the role of brightness up/down
button to swap.

Experiments showed the FPR30 register caused this behavior. Moreover,
even if this register don't have side-effect on other systems, over-
writing it is also highly questionable, since it was originally
configurated by the motherboard manufacturer by hardwiring pull-down
resistors to indicate the type of LCD panel. We should not mess with
it.

Stop writing to the SR30 (a.k.a FPR30) register.

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 | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/video/fbdev/sm712fb.c
+++ b/drivers/video/fbdev/sm712fb.c
@@ -1145,8 +1145,8 @@ static void sm7xx_set_timing(struct smtc

/* init SEQ register SR30 - SR75 */
for (i = 0; i < SIZE_SR30_SR75; i++)
- if ((i + 0x30) != 0x62 && (i + 0x30) != 0x6a &&
- (i + 0x30) != 0x6b)
+ if ((i + 0x30) != 0x30 && (i + 0x30) != 0x62 &&
+ (i + 0x30) != 0x6a && (i + 0x30) != 0x6b)
smtc_seqw(i + 0x30,
vgamode[j].init_sr30_sr75[i]);