On 2017-08-02 02:15, Pandiyan, Dhinakaran wrote:
On Mon, 2017-07-31 at 15:41 -0700, Puthikorn Voravootivat wrote:
But now you're suggesting another arbitrary narrow selection of panels
based on limited evidence.
I understand your point that the panel I observe is not the
representative of the real world.
My point is that we don't know that the panel will work or not unless
we test all panel in the world.
And blacklist would be too much work to maintain and whitelist would
make this code too limited.
As standard adoption should be better over time, I suggest that the
newer panel should have
better implement of the standard than older panel. And I suggest that
eDP 1.4 should be a good
heuristic for the "newer panel" based on these 2 reasons
1. Even though it is a limited evident, David and I independently saw
unrelated eDP 1.3 panel that
implement this feature incorrectly.
2. eDP 1.4 is the first version that support AUX backlight enablement.
TCON vendor probably also
make sure the AUX backlight brightness ajustment works when testing
that feature.
Is this make sense?
Thanks.
I tried to investigate this a little bit and found a device that
reproduces the issue. The backlight does not come back up after a
suspend-resume cycle because the PWM controller does not get enabled at
resume. However, things just work at boot because the BIOS happens to
enable PCH PWM at boot and the panel lights up via the BL_PWM_PIN. Like
you said, this could be because some eDP 1.3 panels have a broken
implementation and eDP 1.4 panels are better. Or, with the BL_PWM_PIN
wired to the board, it simply overrides the DPCD settings. I decided to
not disconnect the PWM pin and test this theory since this was a
development laptop. In summary, I am not really sure blacklisting all
eDP 1.3 panels is the best idea. Also, I don't know how many eDP 1.4
panels this has been tested to correctly work on.
Anyway, since we have four panels that do not work, we could check if
these are the same model/make etc. and blacklist them if there's a
common thread.
The panel in my system is made by LG, model LP140QH1-SPF1.
Kind regards, David
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