[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 #42 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to Jesse Barnes from comment #41)
> Well, it's definitely possible we have to re-program the PWM params as those
> are panel specific; I think the VBT is supposed to be updated with the
> correct values.
> 
> Jani, do we trust those these days?  Maybe current bits will behave better?

No, we don't look at the PWM freq in VBT, we just use whatever the BIOS used at
boot. Which *should* be the same thing.

I had patches eons ago to use the VBT freq, but I haven't updated them in a
while. The VBT has the frequency in Hz (which I think is a surprisingly sane
choice) but translating that to the register value depends on clocks and needs
a bunch of platform specific code. And I'm not really sure it's worthwhile to
be adding that for the oldest gens.

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