[PATCH] modesetting: prefer primary crtc when picking over nothing

Keith Packard keithp at keithp.com
Wed Aug 3 05:09:03 UTC 2016

Dave Airlie <airlied at gmail.com> writes:

> So we had a bug report that epiphany was rendering slow on
> modesetting + DRI3, that I tracked down to the fact it was
> rendering offscreen to a single buffer. However due to this
> rendering being offscreen we were getting the fake crtc
> chosen by the X server as the window didn't overlap any
> active CRTCs.

It looks like that's just a bug -- if they don't want to be throttled,
they should fix the swap interval on their crazy redirected and
off-screen window.

> This didn't happen on amdgpu and I ported this patch across,
> but I believe this only fixed this problem by accident,
> it always picks the primary crtc when it needs one.

That means you're never getting the 1fps throttling setting if a screen
is lit up?

> But this fixes it here for me, the question is whether
> we should do better at picking the fake crtc and whether
> we should be throttling things.

I'd say no; the throttling behaviour is designed to reduce power
consumption when an application isn't visible.

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