[Bug 72289] [GM45 backlight] LCD waterfall effect on HP 2230s laptop

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=72289

--- Comment #38 from Joonas Saarinen <jza at saunalahti.fi> ---
Will do.

The backlight range seems correct now, although the range becomes wrong once I
write the new backlight PWM value. Anyway, before manually setting the new
value, the display still has the wavy effect, so problem remains.

So how does this work? If done properly, should it be the responsibility of the
video BIOS to set the correct PWM value already when the machine is started? I
know that there has been batches of this computer sold with both CMO and SEC
panel. So maybe the former works properly, but with low frequency the internal
temporal dithering in the SEC display goes haywire and HP did not account for
this? But then again, the Windows driver takes care of it, which makes me
almost wonder that there is some exception for this panel baked in. Maybe not,
though.

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