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Date:   Sun, 31 Mar 2019 13:19:07 +0100
From:   Sudip Mukherjee <>
To:     Yifeng Li <>
Cc:     Teddy Wang <>,
        Bartlomiej Zolnierkiewicz <>,,,,
Subject: Re: [PATCH 2/8] fbdev: sm712fb: fix brightness control on reboot,
 don't set SR30.

On Sun, Mar 17, 2019 at 06:24:58AM +0800, Yifeng Li wrote:
> 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 <>
> Cc:  # v4.4+

Tested-by: Sudip Mukherjee <>


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