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fbdev: sm712fb: fix brightness control on reboot, don't set SR30 

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>
This commit is contained in:
Yifeng Li 2019-04-01 17:46:58 +02:00 committed by Bartlomiej Zolnierkiewicz
parent 8069053880
commit 5481115e25
1 changed files with 2 additions and 2 deletions
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4
drivers/video/fbdev/sm712fb.c
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@ -1145,8 +1145,8 @@ static void sm7xx_set_timing(struct smtcfb_info *sfb)
/* 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]);