[Bug 94245] Lubuntu 1404 Kernel 3.19 the DDI1_BKLTCTL is no signal at S3

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94245

--- Comment #9 from shadow <shadow.yang at advantech.com.tw> ---
(In reply to Jani Nikula from comment #5)
> (In reply to shadow from comment #0)
> > -- Display connector: HDMI, DP, VGA
> > 
> > The DDI1_BKLTCTL has output at S3 resume on WIN7 /8, but Lubuntu 1404 Kernel
> > 3.19 the DDI1_BKLTCTL is no signal at S3 resume.
> 
> What is DDI1_BKLTCTL exactly? Is that some PWM output pin on your board, or
> in some display connector?
>
> In any case, per the dmesg and xrandr, your displays are not identified as
> an eDP (embedded display port) output. We don't have SoC PWM support for
> external displays or other PWM pins.
> 
> What is your use case? Is this a somehow misconfigured eDP port, or do you
> need the PWM signal for something else?

The DDI1_BKLTCTL is same as CRB, it is DDI backlight PWM signal. Please
reference the "DDI BKLT.png".
In our circuit, it is connected to CH7511B PWM input. And the CH7511B just only
bypass the signal to LVDS panel. Please reference the "CH7511 PWM.png" and
"LVDS panel.png". The Chrontel CH7511B is eDP to LVDS bridge.


The DDI1_BKLTCTL is PWM signal. It can be used at Windows OS. Does it not use
at the Linux OS?

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